Morphological and behavioral sex reversal in mermithid-infected mayflies - S. A. Vance (Proceedings of the Royal Society of London, 1996)

Competition and relatedness between queens of the facultatively polygynous ant Myrmica tahoensis - J. D. Evans (Animal Behaviour, 1996)

The ant/plant relationship of Formica and Helianthella - S. Merz (1996)

Untangling multiple factors in spatial distributions: Lilies, gophers, and rocks - P. Legendre; G. D. Weiblen; S. Alfaro; B. A. Thomson; James D. Thomson (Ecology, 1996)
Despite broad consensus on the power of experiments, correlational studies are still important in ecology, and may become more so as spatial studies proliferate. Conventional correlation analysis, however, (1) fundamentally conflicts with the basic ecological concept of limiting factors, and (2) ignores spatial structure in data, which can produce spuriously high correlations. Especially for field data, bivariate scattergrams often show factor—ceiling" distributions wherein data points are widely scattered beneath an upper limit, due to the action of other factors. Although most ecological information in such a graph resides in the upper limit, standard correlation/regression does not characterize such limits. If other factors have been measured, path analysis may be useful, but otherwise, direct description of ecological ceilings is desirable. Objective methods for doing so are barely known to ecologists; we review recent proposals for statistical testing and data display. For correcting correlations for spatial patchiness of the variables, another new technique has been proposed by Clifford, Richardson, and Hemon: by reducing the effective sample size to account for the autocorrelation it allows significance tests. We discuss these issues with reference to counts of glacier lily (Erythronium grandiflorum) seedlings, vegetative plants, and flowering plants in a square grid of 256 contiguous $2 × 2$ m quadrats in subalpine meadow in western Colorado. We also measured soil moisture, pocket gopher activity, and soil rockiness. All six variables showed significant patchiness (spatial autocorrelation) at similar scales. The abundance of flowering plants was positively correlated with rockiness and negatively correlated with moisture and gopher activity. Although limited seed dispersal suggests that seedlings should be spatially associated with flowering plants, no such correlation existed: indeed, examination of the bivariate scatterplot suggests a negative association, in the particular and restricted sense that seedlings are abundant only in quadrats where flowering is low. We hypothesize that seed germination is higher in less rocky areas of deeper, moister soil than in the rocky areas where most seeds land, but that seedlings seldom reach maturity unless they are in a rocky refuge from predation. Results from path analysis are consistent with this hypothesis. Such an ecological situation should weaken natural selection on characters enhancing seed dispersal.

Insect herbivory as a major factor in the shade distribution of a native crucifer (Cardamine cordifolia A. Gray, bittercress) - S. M. Louda; J. E. Rodman (Journal of Ecology, 1996)
Svata M. Louda, James E. Rodman, Insect Herbivory as a Major Factor in the Shade Distribution of a Native Crucifer (Cardamine Cordifolia A. Gray, Bittercress), Journal of Ecology, Vol. 84, No. 2 (Apr., 1996), pp. 229-237

Noteworthy collections: Colorado - R. V. Seagrist; K. J. Taylor (Madro¤o, 1996)

Generalization in pollination systems, and why it matters - N. M. Williams; J. Ollerton; L. Chittka; Mary V. Price; Nickolas M. Waser (Ecology, 1996)
One view of pollination systems is that they tend toward specialization. This view is implicit in many discussions of angiosperm evolution and plant—pollinator coevolution and in the long—standing concept of pollination syndromes. But actual pollination systems often are more generalized and dynamic than these traditions might suggest. To illustrate the range of specialization and generalization in pollinators' use of plants and vice versa, we draw on studies of two floras in the United States, and of members of several plant families and solitary bee genera. We also summarize a recent study of one local flora which suggests that, although the colors of flowers are aggregated in phenotype space, there is no strong association with pollinator types as pollination syndromes would predict. That moderate to substantial generalization often occurs is not surprising on theoretical grounds. Plant generalization is predicted by a simple model as long as temporal and spatial variance in pollinator quality is appreciable, different pollinator species do not fluctuate in unison, and they are similar in their pollination effectiveness. Pollinator generalization is predicted when floral rewards are similar across plant species, travel is costly, constraints of behavior and morphology are minor, and/or pollinator lifespan is long relative to flowering of individual plant species. Recognizing that pollination systems often are generalized has important implications. In ecological predictions of plant reproductive success and population dynamics it is useful to widen the focus beyond flower visitors within the correct" pollination syndrome, and to recognize temporal and spatial fluidity of interactions. Behavioral studies of pollinator foraging choices and information—processing abilities will benefit from understanding the selective advantages of generalization. In studies of floral adaptation, microevolution, and plant speciation one should recognize that selection and gene flow vary in time and space and that the contribution of pollinators to reproductive isolation of plant species may be overstated. In conservation biology, generalized pollination systems imply resilience to linked extinctions, but also the possibility for introduced generalists to displace natives with a net loss of diversity.

Effects of manipulated soil microclimate on mesofaunal biomass and diversity - V. Price; A. Rawa; John Harte (Soil Biology and Biochemistry, 1996)

Upper mantle shear structure beneath the Colorado Rocky Mountains - Stephen P. Grand; Duk‐Kee Lee (Journal of Geophysical Research: Solid Earth, 1996)
A tomographic inversion of teleseismic shear wave delays has been performed using data collected in the 1992 Program for Array Seismic Studies of the Continental Lithosphere Rocky Mountain Front experiment. The shear wave residuals used as data were corrected for known crustal, sediment and topographic differences and thus were sensitive to mantle shear velocity variations beneath the Colorado array. Large differences in shear wave travel time are observed across Colorado and into western Kansas with a maximum difference of near 5 sec between the central Rockies in Colorado and a station in western Kansas. The shear wave residuals were inverted for shear wave velocity variations in the upper 350 km of the mantle beneath Colorado and Kansas. Large differences in mantle shear velocity are found between the Rockies and the Kansas Great Plains. The average shear velocity in the upper 200 km is about 9% greater beneath Kansas than beneath the Rockies. At greater depths, lateral variations are far smaller and not as well correlated with surface tectonics. In a qualitative sense, there appear to be three mantle structures present beneath the study area. Beneath the Rockies the upper mantle is extremely slow. Both to the west and east of the Rockies we find intermediate mantle shear velocity. There is then an abrupt increase in mantle shear velocity near the Colorado‐Kansas border. We interpret the abrupt increase in mantle shear velocity near the Colorado‐Kansas border to mark the boundary of cratonic lithosphere. The slow velocity zone beneath the Rockies appears to be upwelled asthenosphere as is seen beneath the Rio Grande Rift to the south. To match the seismic contrast between the mantle beneath Kansas and the Colorado Rockies requires a temperature contrast of at least 350° C as well as partial melt beneath the Rockies. The hot mantle beneath the Rockies implies that the mantle density is low and the high topography of the Rockies is at least partially due to buoyant mantle.

Colorado Potato Beetle Control; Asana Wettable Powder Efficacy Trial, Grand Forks, Nd, 1994 - Carlyle Holen; David M. Noetzel; Jennifer Miller (Arthropod Management Tests, 1996)
Abstract Certified B-sized potato seed was planted at the Red River Valley Potato Growers Research farm on 20 May. Soils were of a finely textured (clay) type. Plot size was 4 rows 36 inch wide and 25 ft. in length. Treatments were arranged in a RCB design, replicated 4 times. Insecticide application were broadcast using a hand held spray and applying at 40 psi. Dry materials were preweighed, all materials were mixed at the site and applied in 20 gal total material per acre. The trial site was extremely wet during July and August. The center two rows of each plot were harvested on 14 Oct.

Colorado Potato Beetle Control; Furadan 4F Comparisons, Grand Forks, Nd, 1994 - Carlyle Holen; David M. Noetzel; Jennifer Miller (Arthropod Management Tests, 1996)
Abstract A field was planted on 11 May using certified B-sized Norchip potatoes. Soils are of a fine texture (clay), and were dry at planting time. Plots were 4 rows 36 inch wide, 25 ft. in length with a 6 ft. alley at the ends. Treatments were arranged in a RCB design, replicated 4 times. Soil treatments were applied into a trench 2 inches above the seed piece on May 11, and covered with dry soil. Foliars were broadcast in 20 gal total material at 40 psi using a hand held CO2sprayer. Application dates were 1, 28 July and 11 Aug. Conditions in July and August were very wet with standing water often present.

Intraguild predation and cannibalism among larvae of detritivorous caddisflies in subalpine wetlands - G. B. Sparks; G. L. Rouse; Heidi Steltzer; W. S. Brown; S. A. Wissinger (Ecology, 1996)
Comparative data from subalpine wetlands in Colorado indicate that larvae of the limnephilid caddisflies, Asynarchus nigriculus and Limnephilus externus, are reciprocally abundant among habitats–Limnephilus larvae dominate in permanent waters, whereas Asynarchus larvae dominate in temporary basins. The purpose of this paper is to report on field and laboratory experiments that link this pattern of abundance to biotic interactions among larvae. In the first field experiment, growth and survival were compared in single and mixed species treatments in littoral enclosures. Larvae, which eat mainly vascular plant detritus, grew at similar rates among treatments in both temporary and permanent habitats suggesting that exploitative competition is not important under natural food levels and caddisfly densities. However, the survival of Limnephilus larvae was reduced in the presence of Asynarchus larvae. Subsequent behavioral studies in laboratory arenas revealed that Asynarchus larvae are extremely aggressive predators on Limnephilus larvae. In a second field experiment we manipulated the relative sizes of larvae and found that Limnephilus larvae were preyed on only when Asynarchus larvae had the same size advantage observed in natural populations. Our data suggest that the dominance of Asynarchus larvae in temporary habitats is due to asymmetric intraguild predation (IGP) facilitated by a phenological head start in development. These data do not explain the dominance of Limnephilus larvae in permanent basins, which we show elsewhere to be an indirect effect of salamander predation. Behavioral observations also revealed that Asynarchus larvae are cannibalistic. In contrast to the IGP on Limnephilus larvae, Asynarchus cannibalism occurs among same—sized larvae and often involves the mobbing of one victim by several conspecifics. In a third field experiment, we found that Asynarchus cannibalism was not density—dependent and occurred even at low larval densities. We hypothesize that Asynarchus IGP and cannibalism provide a dietary supplement to detritus that may be necessary for the timely completion of development in these nutrient—poor, high—elevation wetlands.

Queen longevity, queen adoption, and posthumous indirect fitness in the facultatively polygynous ant Myrmica tahoensis - J. D. Evans (Behavioral Ecology, 1996)

Floral mimicry, coevolution of hosts and pathogens, and stress tolerance versus resistance to pathogens - B. A. Roy (Bulletin of the Geobotanical Institute ETH, 1996)

Temporal and spatial variation in reproduction in the facultatively polygynous ant Myrmica tahoensis (Hymenoptera: Formicidae) - J. D. Evans (Ins. Soc., 1996)

Distribution and habitat characterization of subalpine chiropteran species - M. A. Garza (1996)

The infection of nymphal Baetis bicaudatus by the mermithid nematode Gasteromermis sp - S. A. Vance; B. L. Peckarsky (Ecological Entomology, 1996)

Stoneflies as ecological engineers - hungry predators reduce fine sediments in stream beds - B. A. Zanatell; B. L. Peckarsky (Freshwater Biology, 1996)

Species diversity and evenness of benthic invertebrates as a measure of the effects of pollution from Gothic campground - J. Greshko (1996)

Benefits of coloniality: increased foraging frequency through the use of information centers in a cliff swallow colony - W. A. Jordan (1996)

Foraging efficiency as related to variance in worker size and colony size in Formica neorufibarbis - L. McClenachan (1996)

A population census and study of interspecific competition between Nicrophorus investigator and Nicrophorus defodiens - S. Richmond (1996)

Using species-area relationship to determine species turnover in terrestrial arthropods - R. Salinas (1996)

Correlation between insect abundance and foraging activity of the sub-alpine bats of Gothic, Colorado - S. Harney (1996)

Sexual dimorphism in tiger salamanders of the kettle ponds of Gothic, Colorado - M. Holderby (1996)

Biodiversity of insect families in three montane habitats - K. Jakubowski (1996)

The effect of size and morphology on the foraging behavior of Ambystoma tigrinum nebulosum - E. B. Johnson (1996)

The species-area relationship and spatial turnover - S. McCarthy (1996)

Prevalence of chiropteran predation by owls of the Gunnison County region - S. Merideth (1996)

The effect of mermithid parasitism on the behavior and ecology of its mayfly host - S. A. Vance (1996)

Wetlands of the Colorado River Delta Maintained by Agricultural Drainage Water - Edward P. Glenn (HortScience, 1996)
The delta of the Colorado River in Mexico historically contained 780,000 ha of riparian, marsh, and gallery forest habitat. Similar to other desert river deltas, such as the Nile and Indus, the lower delta of the Colorado River has been severely affected by the upstream diversion of water for human use. However, several large marsh areas of conservation interest still occur below the agricultural fields in Mexico. They are supported by flood water, agricultural drainage water, and municipal sewage effluent, as well as by seawater in the intertidal zone. The main anthropogenic marshes are the Rio Hardy wetland, maintained by geothermal discharge and Mexicali irrigation return flows in the western delta, and Cienega de Santa Clara, maintained by local irrigation return flows and by discharge of Wellton-Mohowk Valley drainage from the United States, imported via a 80-km canal to Mexico. These wetlands provide valuable habitat to resident and migratory waterfowl, shorebirds, mammals, and endangered species, including the Yuma Clapper Rail and the Desert Pupfish. Both wetlands are currently threatened by water management actions that do not take the wetland value of agricultural drainage into consideration. If agricultural drainage water and other available waste streams were explicitly managed to support wetlands, the Colorado River detla could potentially contain 50,000 ha or more of permanent, high-quality brackish wetlands below the agricultural fields.

Solitary behavior in a high-altitude population of the social sweat bee Halictus rubicundus (Hymenoptera: Halictidae) - J. M. Eickwort; G. C. Eickwort; JAMES H. Gordon; M. A. Eickwort (Behav Ecol Sociobiol, 1996)

Differential behavioural responses of mayflies from stream with and without fish to trout odour - A. R. McIntosh; B. L. Peckarsky (Freshwater Biology, 1996)
1. In streams, mayflies (Order Ephemeroptera) are at risk from fish feeding visually in the water column. The effect of fish odour on the behaviour of Baetis bicaudatus from a fishless stream and a trout stream was investigated in four large oval tanks supplied with water from the fishless stream.2. For each mayfly population, mayfly positioning on the substratum and movement in the water column (drift) were measured during the day and night, over 3 days. Brook trout (Salvelinus fontinalis) odour was added to two tanks to test the effect of a threat from fish.3. Throughout the experiment more mayflies from the trout stream were observed on the substratum surface and in the water column during the night than the day, but the magnitude of night drift was less in tanks with fish odour.4. Baetis from the fishless stream also displayed a nocturnal periodicity in drift and positioning, but their night‐time drift was not affected by the presence of fish odour. On the first day of the experiment, however, more mayflies were observed on the substratum surface and drifting in tanks without fish odour during the day.5. Sensitivity to fish odour may enable mayflies to alter their behaviour according to the risk of predation from fish.

Population time budget for the yellow-bellied marmot - R. C. Grey; A. Kovach; E. L. Barthelmess; C. M. Salsbury; Kenneth B. Armitage (Ethology, Ecology and Evolution, 1996)
Time budgets for 17 behaviors were analyzed for cohort, day-period, season- period and interactions among the main effects for three colonies of yellowbellied marmots in the Upper East River Valley in western Colorado. These effects explained up to 79% of the variation in the behaviors. Marmots allocated more time (40-60%, 110-265 min daily) above-ground to sitting/lying than to any other activity. Foraging was the other major activity (12-23%, 37 to 94 min daily). Vigilance/alert varied from 1.1 to 14.5% and from 12.0 to 71.7 min daily. Social status affected the time budget, especially time allocated to vigilance/alert. All other behaviors averaged about 5% or less except for out-of-sight and enterburrow. The adult male cohort spent significantly more time above-ground than all other cohorts and reproductive females allocated significantly more time to foraging than the other cohorts. The amount of time spent above-ground decreased linearly from the down-river site to the up-river site. The proportion of time spent above-ground was significantly less at mid day than in the morning or afternoon. Above-ground activity was lowest during gestation, increased during lactation, remained high during early post-lactation, and declined during the final season-period. The following significant relationships common to the three colonies suggest species characteristics or common environmental influences: more time allocated to foraging and foraging-vigilance in the afternoon and more time allocated to foraging-alert, alert, and locomotion during gestation and lactation than during post-lactation. Marmots adjust their behaviors according to prevailing conditions. The remaining significant relationships can be attributed to specific age-sex cohorts or to habitat differences. Because marmots allocate so much time to sitting/lying, we suggest that energy budgets are not constrained by foraging time but by time required to process ingested food. Similarly, time spent vigilant/alert does not seem to constrain energy intake. Social behavior is not limited by time, but could easily be expanded by spending less time inactive. In general, there do not seem to be tradeoffs among activities. Among other species of ground-dwelling sciurids, social behavior occupies a small proportion of the time budget, but the amount of time allocated to foraging and sitting/lying varies widely.

Alternative predator avoidance syndromes of stream-dwelling mayfly larvae - B. L. Peckarsky (Ecology, 1996)
Experiments were conducted to compare the patterns, mechanisms, and costs of predator avoidance behavior among larvae of five species of mayflies that co—occur with the predatory stoneflies, Megarcys signata and Kogotus modestus in western Colorado streams. Mayfly drift dispersal behavior, use of high vs. low food (periphyton or detritus) patches, microhabitat use, positioning, and activity periodicity were observed in the presence and absence of predators in circular flow—through chambers using natural stream water. Also, distances from predators at which prey initiated escape responses were compared among prey and predator species. Costs of predator avoidance behavior were assessed by measuring short—term (24 h) feeding rates of mayflies in the presence or absence of predatory stoneflies whose mouthparts were immobilized (glued) to prevent feeding. The intensity and associated costs of predator avoidance behavior of mayfly species were consistent with their relative rates of predation by stoneflies. Megarcys consumes overwintering generation Baetis bicaudatus > Epeorus longimanus > Cinygmula = Ephemerella; Kogotus consumes summer generation Baetis > Epeorus deceptivus = Cinygmula; Megarcys eats more mayflies than Kogotus. While Megarcys induced drift by Baetis, Epeorus, and Cinygmula, this disruptive predator avoidance behavior only reduced food intake by Baetis and Epeorus. The morphologically defended mayfly species, Ephemerella, neither showed escape behavior from Megarcys, nor any cost of its antipredatory posturing behavior. Only Baetis responded by drifting from Kogotus. No mayfly species shifted microhabitats or spent less time on high—food patches in the presence of foraging stoneflies. However, predators enhanced the nocturnal periodicity of Baetis drift, which was negligible in the absence of stoneflies as long as food was abundant. Lack of food also caused some microhabitat and periodicity shifts and increased the magnitude of both day and night drift of Baetis. Thus, Baetis took more risks of predation by visual, drift—feeding fish not only in the presence of predatory stoneflies, but also when food was low or they were hungry. All other mayflies were generally nocturnal in their use of rock surfaces, as long as food was abundant. Finally, the distances at which different mayfly species initiated acute escape responses were also consistent with relative rates of predation. This study demonstrates alternative predator avoidance syndromes by mayfly species ranging from an initial investment in constitutive morphological defenses (e.g., Ephemerella) to induced, energetically costly predator avoidance behaviors (e.g., Baetis). Although the costs of Ephemerella's constitutive defense are unknown, experiments show that prey dispersal is the mechanism underlying fecundity costs of induced responses by Baetis to predators, rather than microhabitat shifts to less favorable resources or temporal changes in foraging activity. A conceptual model suggests that contrasting resource acquisition modes may account for the evolution and maintenance of alternative predator avoidance syndromes along a continuum from Baetis (high mobility) to heptageniids (intermediate mobility) to Ephemerella (low mobility). Prey dispersal (swimming) to avoid capture results in reduction of otherwise high fecundity by Baetis, which trades off morphological defense for enhanced ability to acquire resources. Thus, improved foraging efficiency is the selection pressure maintaining the highly mobile life style in Baetis, which increases resource acquisition and fecundity, offsetting the high mortality costs associated with this behavior.

Land Use and Landscape Change in the Colorado Mountains II: A Case Study of the East River Valley - H. Gosnell; D. M. Theobald; W. E. Riebsame (Mountain Research and Development, 1996)
D. M. Theobald, H. Gosnell, W. E. Riebsame, Land Use and Landscape Change in the Colorado Mountains II: A Case Study of the East River Valley, Mountain Research and Development, Vol. 16, No. 4 (Nov., 1996), pp. 407-418

Does pollination matter to Polygonum douglasii? - R. Robles (1996)

Summer population structure of subalpine bats in Colorado - J. F. Storz; C.F. (Rick) Williams (Southwestern Naturalist, 1996)

Floral biology - P. T. Wilson; James D. Thomson (1996)

The effect of the mermithid parasite Gasteromermis sp. (Nematoda: Mermithidae) on the drift behaviour of its mayfly host, Baetis bicaudatus (Ephemeroptera: Baetidae): a trade-off between avoiding pred - S. A. Vance (Canadian Journal of Zoology, 1996)

Ectoparasites, fitness, and social behaviour of yellow-bellied marmots - D. H. Van Vuren (Ethology, 1996)
AbstractParasites can cause a loss of fitness for their hosts, potentially influencing social behaviour patterns of the host that promote or hinder parasite transmission. I studied yellow‐bellied marmots (Marmota flaviventris) and their ectoparasites to determine if ectoparasites reduce the fitness of marmots and to test whether ectoparasite loads differ according to social behaviour. Three taxa of ectoparasites were identified, fleas (Oropsylla Stanfordi), lice (Linognathoides marmotae), and mites (family Dermanyssidae). High ectoparasite loads were related to slower growth, lower overwinter survival, and reduced reproduction, suggesting that ectoparasites are a fitness cost for marmots. Ectoparasite loads were not higher in colonial than in noncolonial marmots, nor in polygynous than in monogamous adult males. There was a trend, however, toward higher ectoparasite loads in marmots that were dispersing rather than philopatric. Further, ectoparasite loads differed among groups of marmots that nested or hibernated communally, indicating that spatial scale is important in understanding the relationships between parasites and social behaviour.

Trapline foraging by bumblebees: I. Persistence of flight-path geometry - James D. Thomson (Behavioral Ecology, 1996)
By setting out arrays of potted plants of Penstemon strictus, I tested whether freely foraging bumblebee (Bombus spp.) workers would establish regular foraging routes that reflected the geometry of the array. They did, passing through an asymmetrical array in a pattern that minimized interplant flight distances. After the array was changed to a symmetrical pattern, however, the experienced bees continued to show their previous asymmetrical flight patterns. New bees without experience on the asymmetrical array showed no asymmetry on the symmetrical array. I term this persistence of flight-path geometry "trapline holdover," and discuss its implications for the study of animals' learning and foraging behavior.

Mating systems and sexual division of foraging effort affect puddling behavior by butterflies - C. E. Sculley; Carol L. Boggs (Ecological Entomology, 1996)
Abstract. 1. Foraging effort can vary among age classes and between the sexes. In many Lepidoptera, young males feed from mud, dung or carrion in a behaviour known as ‘puddling’, whereas females rarely puddle. In at least one species, males transfer sodium gained from puddling to females at mating for use in egg production. 2. Here we examine sex‐ and age‐specific puddling patterns in seven montane butterfly species. We also test the hypothesis that among species in which young males predominate at puddles, differences in age‐ and sex‐specific puddling patterns for a given species are related to mean female lifetime mating numbers. 3. For five species, young males fed proportionately more at puddles than other sex and age classes. Two species showed anomalous feeding patterns. In one, young females predominated at puddles; in the other, butterflies were rarely found at flowers. 4. As predicted, among the five species in which young males feed proportionately more at puddles, mean number of lifetime matings by females was negatively correlated with frequency of mud puddling by older females. A second prediction that mean number of lifetime matings by females is positively correlated with frequency of mud puddling by older males was not supported. 5. The results provide support for interspecific variation in division of responsibility between the sexes for resource acquisition for female reproduction, indicating close coordination between the sexes of foraging and life‐history tactics.

A plant pathogen influences pollinator behavior and may influence reproduction of nonhosts - B. A. Roy (Ecology, 1996)
Some plant pathogens attract pollinating insects and thus have the potential to influence the pollination of flowers, just as different flower species can influence one another's pollination. Showy, flower—like pseudoflowers caused by the rust fungus Puccinia monoica on Arabis holboellii (Brassicaceae) commonly co—occur with flowers of Anemone patens (Ranunculaceae). I evaluated the effects of pseudoflowers and anemone on each other's visitation, and the effect of pseudoflowers on the seed set of anemone. I expected that at low overall “flower” densities visitation would be facilitated in patches containing a mixture of these species. At low densities, pseudoflowers or flowers alone may be too rare to attract sufficient visitors, but the addition of the other species could make mixtures more attractive and thus increase visitation rates. At high densities I expected that “flower” in mixtures would compete for pollinators because it is more energy efficient for pollinators to concentrate visits on the most rewarding species. I used artificial arrays to separate the effects of “flower” density and relative frequency on visitation. Local density was not a good predictor of the influence of one species on the other. Instead, visitation patterns depended most strongly on the kind of visitor (flies vs. bees). Visitation to A. patens by flies was facilitated by the presence of pseudoflowers at both high and low densities, whereas visitation to pseudoflowers was not significantly influenced by A. patens at either density. Local density affected visitation by bees, but relative frequency did not. In addition to observing visitation, I also quantified the effects of interspecific movement of both pollen and spores on the reproductive success of A. patens. Although the presence of pseudoflowers sometimes facilitates visitation to A. patens, this effect could be counterbalanced by competition through interspecific insect movement: sticky pseudoflowers remove pollen from visiting insects, and fungal spermatia deposited on flower stigmas reduce seed set.

Detectability, philopatry, and the distribution of dispersal distances in vertebrates - W. D. Koenig; P. N. Hooge; D. H. Van Vuren (Trends in Ecology and Evolution, 1996)
The inadequacy of dispersal data obtained directly by traditional methods using population studies of marked individuals is highlighted by comparing the resulting distributions with dispersal estimates obtained by radio-tracking and by using genetic estimates of gene flow.

Evolution of floral traits in a hermaphroditic plant: field measurements of heritabilities and genetic correlations - Diane R. Campbell (Evolution, 1996)
Genetic variances, heritabilities, and genetic correlations of floral traits were measured in the monocarpic perennial Ipomopsis aggregata (Polemoniaceae). A paternal half-sib design was employed to generate seeds in each of four years, and seeds were planted back in the field near the parental site. The progeny were followed for up to eight years to estimate quantitative genetic parameters subject to natural levels of environmental variation over the entire life cycle. Narrow-sense heritabilities of 0.2-0.8 were detected for the morphometric traits of corolla length, corolla width, stigma position, and anther position. The proportion of time spent by the protandrous flowers in the pistillate phase ("proportion pistillate") also exhibited detectable heritability of near 0.3. In contrast, heritability estimates for nectar reward traits were low and not significantly different from zero, due to high environmental variance between and within flowering years. The estimates of genetic parameters were combined with phenotypic selection gradients to predict evolutionary responses to selection mediated by the hummingbird pollinators. One trait, corolla width, showed the potential for a rapid response to ongoing selection through male function, as it experienced both direct selection, by influencing pollen export, and relatively high heritability. Predicted responses were lower for proportion pistillate and corolla length, even though these traits also experienced direct selection. Stigma position was expected to respond positively to indirect selection of proportion pistillate but negatively to selection of corolla length, with the net effect sensitive to variation in the selection estimates. Anther position also was not directly selected but could respond to indirect selection of genetically correlated traits.

Colonization and reproduction of the epibiotic flagellate Colacium vesiculosum (Euglenophyceae) on Daphnia pulex - R. S. Al-Dhaheri; R. L. Willey (Journal of Phycology, 1996)
ABSTRACTThe epibiotic flagellate Colacium vesiculosum Pringsheim attaches to planktonic species of Daphnia in freshwater habitats. Previous studies found that prevalence (percentage of substrate organisms carrying attached epibionts) and intensity (number of attached epibionts on a given substrate organism) are low early in the Daphnia intermolt period and are high late in the intermolt period. We tested the hypothesis that increases of Colacium cells attached to Daphnia occur both by rapid initial and continuous colonization and by cell reproduction. Epibiont prevalence and intensities were determined at successive intermolt stages of Daphnia pulex Leydig collected from freshwater ponds in Colorado. Colonization was continuous throughout the intermolt period and was most important to epibiont population increase at the beginning of the intermolt period. Cell division was the major contributor to epibiont increase at the end of the intermolt period.

The effect of macroinvertebrate prey on the cannibalistic polymorphism in the tiger salamander Ambystoma tigrinum nebulosum - A. VanDeusen (1996)

Growth and survival of juvenile yellow-bellied marmots (Marmota flaviventris) - C. Lenihan; D. H. Van Vuren (Canadian Journal of Zoology, 1996)
We compared patterns of growth in juvenile yellow-bellied marmots (Marmota flaviventris) between 2 years in which precipitation differed, and we determined if mass at entry into hibernation affects over-winter survival. Juveniles exhibited an asymptotic growth pattern with mass gain for a mean of 60.8 days, followed by stable mass until entry into hibernation. Growth ceased in early September, shortly after the end of the plant growing season. Juveniles born in 1991, a year of late snowmelt and low summer precipitation, entered into hibernation at significantly lower mass than juveniles born in 1992. Juveniles born in 1992 survived better despite experiencing a long winter during which they spent more days in hibernation and lost more mass. Overall, heavier juveniles were more likely to survive hibernation. Further, mass at entry into hibernation apparently had a greater effect on over-winter survival than did winter severity.

Mechanisms of hummingbird-mediated selection for flower width in Ipomopsis aggregata - Mary V. Price; Nickolas M. Waser; Diane R. Campbell (Ecology, 1996)

Influence of cattle grazing on timing of post-breeding migration of Ambystoma tigrinum nebulosum - Charles Kelly (1996)

Parental care and mate guarding in the apparently monogamous mountain bluebird, Sialia currucoides - Charles Kelly (1996)

Microdistributions, food resources and feeding habits of filter-feeding Trichoptera in the Upper Colorado River - Neal J. Voelz; James V. Ward (Archiv für Hydrobiologie, 1996)
A year-round study was conducted in the Colorado River, USA, to examine microdistributions and feeding habits of the filter-feeding Trichoptera (caddisflies) Arctopsyche grandis, Brachycentrus occidentalis and Hydropsyche cockerelli. Only one significant relationship was found between individual rock surface area and the density of larvae during the sampling periods. Contrary to our predictions that current exposed microhabitats would be selected, all species occurred primarily on the bottom and lower lateral sides of rocks at all sites. Clumped distributions in the absence of spatial segregation by size class suggest common microhabitat preferenda for species and instars. Organic seston in the study reach consisted primarily of detritus, diatoms and Closterium sp. (a green alga). The diets of B. occidentalis and H. cockerelli generally corresponded with the observed proportions of food resources in the seston. Based on HORN'S index, we found high intraspecific dietary overlap for A. grandis and H. cockerelli. Dietary overlap was usually lower between A. grandis and other species. Dietary overlap between B. occidentalis and H. cockerelli larvae was high for most months. Ontogenetic niche shifts, especially in microhabitat use, were demonstrated in this study. The similar use of microhabitat, and the species- specific feeding habits by the filter-feeding Trichoptera suggest that examining relationships at a finer scale is important for a more thorough understanding of species' habitat requirements and overall distribution patterns.

Costs and benefits of sociality in yellow-bellied marmots (Marmota flaviventris): do noncolonial females have lower fitness? - C. Lenihan; C. Lenihan; D. H. Van Vuren (Ethology, Ecology and Evolution, 1996)
Whether an animal lives alone or in a group may have fitness consequences. Among yellow-bellied marmots (Marmota flaviventris), fitness is thought to be lower for noncolonial than for colonial females because juvenile survival, as indicated by trapping, is lower. Trapping, however, may not be an accurate estimate of survival. Low recapture rates of noncolonial juveniles may result from early dispersal due to maternal behavior, or higher mortality due to predation or inadequate resources for overwinter survival. Our objective was to determine if survival was lower for noncolonial than for colonial juveniles, and to determine the cause of the low recapture rate of noncolonial juveniles. Our results show that survival of noncolonial juveniles was not lower than that of colonial juveniles. Noncolonial juveniles were not more vulnerable to predation during the active season, nor was overwinter mortality higher. Some noncolonial juveniles did disperse early, and most moved away from the natal burrow to hibernate, thereby explaining the low recapture rate reported previously. Early dispersal was not related to maternal behavior. Noncolonial females do not enjoy the benefits of group-living, especially the opportunity to form matrilines; but they also do not suffer the costs, such as competition for resources.

A comparison of avian species diversity in the Gothic area and Crested Butte - A. McMellan (1996)

The short-term effects of cattle grazing on caddisfly populations - L. Beasley (1996)

The effects of various concentrations of fish chemicals on mayfly behavior - M. Robertson (1996)

Biodiversity in marmots (1996)

Can montane landscapes recover from human disturbance? Long-term evidence from disturbed subalpine communities - C. G. Curtin (Biological Conservation, 1995)
It is found that, after over 100 years, these disturbed plant communities remained distinct from similar surrounding undisturbed areas, suggesting that biotic factors structure vegetation communities even hundreds of years following disturbance.

Patterns and mechanisms of invasion of conifer (Abies lasiocarpa and Picea engelmanni) into aspen forest and montane meadow - J. Downing; John Harte (1995)

Study of dust accumulation on roadside vegetation along Gothic Road - M. Pengra (1995)

The core of the Black Canyon Computer Corporation - J. Couleur (IEEE Annals of the History of Computing, 1995)
The author discusses his experiences with the GEC computer department, starting with the M236, a high speed 36-bit minicomputer. He discusses the GE 600 lineage, the GE 600/645 and paging, tape transport problems, and the end of the department.

A comparison of resource allocation to reproduction and pollinator visitation to Delphinium nelsonii and Lupinus argentis - C. Kokesh (1995)

Oviposition patterns and larval success of a pre-dispersal seed predator attacking two confamilial host plants - Alison K. Brody; Nickolas M. Waser (Oikos, 1995)
Phytophagous insects that deposit eggs directly on hosts confront a plant world of variable quality. Some studies to date provide evidence for positive relationships between the site of oviposition and offspring success, as expected if females choose sites of high quality or if they or their offspring manipulate host physiology. We studied relationships between oviposition site and larval success for the anthomyiid fly Hyle-mya sp., a predispersal seed predator of the confamilial montane plants Polemonium foliosissimum and Ipomopsis aggregata. The intensity of oviposition on a given P. foliosissimum plant was a good predictor of attack in the following year, suggesting choosiness of female flies. However, larval survival did not decline detectably when eggs were transferred among flowers within or between plants, compared to survival where the female fly originally had deposited the eggs. Also, P. foliosissimum flowers with eggs did not have a higher probability of setting fruit than those without. In contrast, I. aggregata flowers on which Hylemya laid eggs had a significantly higher probability of setting fruit than flowers chosen at random ; this probability did not decline if eggs were removed experimentally. These results suggest that female flies are choosing among I. aggregata flowers in an adaptive manner, or manipulating their quality on behalf of offspring.

Epibiont populations on Daphnia: effects of habitat patch dispersion on metapopulation dynamics - D. A. Chiavelli (1995)

Relatedness threshold for the production of female sexuals in colonies of a polygynous ant, Myrmica tahoensis, as revealed by microsatellite DNA analysis - J. D. Evans (Proceedings of the National Academy of Sciences, USA, 1995)
The genetic relationships of colony members in the ant Myrmica tahoensis were determined on the basis of highly polymorphic microsatellite DNA loci. These analyses show that colonies fall into one of two classes. In roughly half of the sampled colonies, workers and female offspring appear to be full sisters. The remaining colonies contain offspring produced by two or more queens. Colonies that produce female sexuals are always composed of highly related females, while colonies that produce males often show low levels of nestmate relatedness. These results support theoretical predictions that workers should skew sex allocation in response to relatedness asymmetries found within colonies. The existence of a relatedness threshold below which female sexuals are not produced suggests a possible mechanism for worker perception of relatedness. Two results indicate that workers use genetic cues, not queen number, in making sex-allocation decisions. (i) The number of queens in a colony was not significantly correlated with either the level of relatedness asymmetry or the sex ratio. (ii) Sex-ratio shifts consistent with a genetically based mechanism of relatedness assessment were seen in an experiment involving transfers of larvae among unrelated nests. Thus workers appear to make sex-allocation decisions on the basis of larval cues and appear to be able to adjust sex ratios long after egg laying.

Middle Jurassic Todilto Formation of northern New Mexico and southwestern Colorado: Marine or nonmarine? - Robert H. Denison; Robert G. Evans; D. W. Kirkland (1995)
Resolution of the controversy about the origin of this evaporitic limestone and gypsum unit is possible only if the position that the Todilto is exclusively marine or exclusively nonmarine is abandoned. The Todilto Formation was deposited in a coastal body of saline water (a salina) adjacent to the Sundance Sea. After an initial flooding by marine water, the salina was maintained by inflow of fresh water from streams, mostly intermittent, and by influx of sea water by seepage through or over-topping of physiographic barriers. The arid climate promoted evaporation, which led to precipitation of laminated carbonates and nodular gypsum. The mixed brine gave its precipitates a distinctive and indelible isotopic signature-the carbon and sulfur isotopic ratios could be interpreted as originating from marine waters, the strontium ratios as being influenced by nonmarine waters. Reconstruction of the Todilto paleoenvironment as a salina reconciles the apparent conflicts in interpretation of chemistry, as well as similar conflicts in interpretation of the paleontology and of the mineralogy and stratigraphy of the Todilto sediments. The Todilto Formation can be seen in widely distributed, conspicuous outcrops in northern NM and southwestern CO. It consists of a Limestone Member typically 5-20 ft thick and a Gypsum Member typically 30-100 ft thick. The distribution of the latter is really more restricted, but where it is absent a Breccia Member may be present. The approximate deposition extents of the Todilto Limestone and Todilto Gypsum Members are shown. For more than 40 years there has been a controversy about the environment of deposition of the Todilto Formation: Was it marine or nonmarine? In this bulletin, the authors combine isotropic, paleontological, and stratigraphic information in an attempt to determine the environment of deposition of the Todilto Formation. Much of this information is new, including all the values for strontium isotopes, and many of the values for carbon and sulfur isotopes. Particularly the strontium isotopic data provides the authors with a new approach to resolving the question of the original depositional setting, an approach that can be used for other deposits of carbonates and evaporites for which the environment is unknown. Also new are data on the distribution of fossil insects and, in part, of fossil fish. Many of the individual pieces of evidence may be equivocal, but when viewed together they lead us to only one conclusion in the authors attempts to resolve this protracted controversy.

The influence of different types of disturbance on insect diversity - C. H. Sekercioglu (1995)

Avalanche intensity and the intermediate disturbance hypothesis - M. Geluardi (1995)

The Unsolicited Chronicler: An Account of the Gunnison Massacre, Its Causes and Consequences, Utah Territory, 1847-1859. - Robert Kent Fielding; James B. Allen (The Journal of American History, 1995)
Journal Article The Unsolicited Chronicler: An Account of the Gunnison Massacre, Its Causes and Consequences, Utah Territory, 1847–1859. By Robert Kent Fielding. (Brookline: Paradigm, 1993. xiv, 474 pp. $49.95, ISBN 0-912111-38-0.) Get access James B. Allen James B. Allen Emeritus Brigham Young University, Provo, Utah Search for other works by this author on: Oxford Academic Google Scholar Journal of American History, Volume 81, Issue 4, March 1995, Pages 1718–1719, https://doi.org/10.2307/2081719 Published: 01 March 1995

Management of Molothrus ater in Gothic, Colorado - S. Nayak (1995)

Global warming and soil microclimate: results from a meadow-warming experiment - F. R. Chang; B. P. Feifarek; K. P. Shen; M. S. Torn; A. P. Kinzig; R. M. Shaw; John Harte (Ecological Applications, 1995)
We used overhead infrared radiators to add a constant increment of °15 W/m2, over 2 yr, to the downward heat flux on five 30‐m2 montane meadow plots in Gunnison County, Colorado, USA. Heating advanced snowmelt by °1 wk, increased summer soil temperatures by up to 3°C, and reduced summer soil moisture levels by up to 25% compared to control plots. Soil microclimate response to heating varied with season, time of day, weather conditions, and location along the microclimate and vegetation gradient within each plot, with the largest temperature increase observed in daytime and in the drier, more sparsely vegetated zone of each plot. Day‐to‐day variation in the daily‐averaged temperature response to heating in the drier zone was negatively correlated with that in the wetter zone. Our experimental manipulation provides a novel and effective method for investigating feedback processes linking climate, soil, and vegetation.

The breeding systems of six species of Arabis (Brassicaceae) - B. A. Roy (American Journal of Botany, 1995)
The ability of organisms to produce genetic variation for any trait, including resistance to pathogens, is partially determined by breeding system. I used enzyme electrophoresis, crossing experiments, and cytology to assess the breeding systems of cooccurring Arabis species that are often infected by rust fungi. The Arabis holboellii surveyed were pseudogamous apomicts with relatively high population‐level ailozyme variation, and variable chromosome numbers (2n, 3n, 4n). Arabisgunnisoniana (3n) and Arabis lignifera (2n) were also pseudogamous but showed no allozyme variation either at the population level, or within progeny arrays. Arabis hirsuta may be an autogamous polyploid or it may be a pseudogamous apomict; more work is needed to clarify the breeding system of this species. Arabis drummondii and Arabis crandallii were sexual, but exhibited little genetic variability due to a predominance of self‐fertilization. The use of several techniques was necessary to evaluate these breeding systems. Insect exclusion indicated when pollen was necessary for seed set, but could not differentiate between sexual reproduction and pseudogamy. Electrophoresis yielded information on the degree of selling (as evidenced by homozygosity) and apomixis (fixed heterozygosity), but could not differentiate between autogamy and apomixis in polyploids without ailozyme variation. Pseudogamy was confirmed when crosses between dissimilar genotypes yielded only the maternal genotype, and cytologically by irregular meiosis.

Control of Colorado Potato Beetle in the Red River Valley, Grand Forks, ND, 1994 - Robert A. Suranyi; Galen C. Thompson; Matthew P. Samuelson; Edward B. Radcliffe (Arthropod Management Tests, 1995)
Abstract Potatoes were planted 17 May at the Research Farm of the Red River Valley Potato Growers Association. Plots were four rows wide, 60 ft long, with 38 in rows and 12 in between plants. Plots were separated on all sides by 6.3 ft of cultivated soil. The experiment had a complete randomized plot design with four replications. Egg masses were flagged 15 Jun and checked daily. Thirty percent egg hatch was estimated to have occurred 22 Jun, but heavy rains and wet field conditions delayed first application of insecticidal sprays until 24 Jun. Subsequent spray applications were made 5, 12 Jul, and 8 Aug. Jun and Jul sprays were targeted against first generation larvae, Aug application against summer generation adults. All applications were made using a tractor-mounted boom sprayer, with a single Teejet nozzle over each row. Sprays were applied in 40 gal of water/acre at 40 psi. Egg masses, small larvae (1st and 2nd instar), large larvae (3rd and 4th instar), and adults were counted 27 Jun, 7, 14 Jul, and 10 Aug on 20 randomly selected plants from the two middle rows of each plot. Tuber yields were estimated by mechanical harvesting one row per plot 2 Sept. Defoliation data were recorded at each evaluation and expressed as mean percent of defoliation across sampling dates. The average number of insect counts across sampling dates are presented in the table. Best control resulted from the use of Furadan, Imidan, and Capture. Yield differences among treatments were not significantly correlated with any measure of insect numbers. Parts of the field were saturated for an extended period of time by heavy Jun rains, which adversely affected yields in all plots. Tuber yields ranged from 136.7 to 207.4 cwt/acre.

Change in terrestrial vegetation and the relating consequences for stream communities - J. Karem; M. McKnight; D. Engelberg; J. L. Hayes (1995)

Report on the conservation status of Veratrum californicum in the Gothic area - M. Hristova (1995)

Cheaters never prosper. Or do they? - S. Magana (1995)

Shifting dominance within a montane vegetation community: results from a climate-warming experiment - R. M. Shaw; John Harte (Science, 1995)
In experimentally heated plots that each span a soil moisture gradient in a Rocky Mountain meadow, aboveground biomass of Artemisia tridentata (a sagebrush) increased in the drier habitat and that of Pentaphylloides floribunda (a shrub cinquefoil) increased in the wetter habitat relative to control plots. In contrast, aboveground forb biomass decreased in the wet and dry habitats of the heated plots. These results, combined with evidence for enhanced sagebrush seedling establishment rates in the heated plots, suggest that the increased warming expected under an atmosphere with a concentration of carbon dioxide twice that of pre-industrial levels could change the dominant vegetation of a widespread meadow habitat.

Seed set and seed mass in Ipomopsis aggregata: variance partitioning and inferences about postpollination selection - R. M. Shaw; Mary V. Price; Nickolas M. Waser (Evolution, 1995)
Events that follow pollination, such as pollen-tube growth and seed maturation, comprise an important phase of angiosperm reproduction. Differential success during this "postpollination" phase may represent phenotypic selection, including sexual selection, or interaction between parents caused, for example, by their genetic similarity. By providing a detailed partitioning of variance in success, diallel crossing designs offer great potential to determine which processes are occurring and their relative magnitudes. We performed three partial diallels with the montane herb Ipomopsis aggregata, using a large sample of parental plants (69 total). Embedded in the designs were crossing-distance treatments of 1 m, 10 m, and 100 m, reflecting a range of parental genetic similarity. We partitioned phenotypic variance in seed set per fruit into six components using restricted maximum-likelihood (REML) analysis. For one diallel, we also partitioned variance in seed mass into five components, and estimated two components of covariance between seed set and mass. Variance caused by maternal effects (Vmat ) comprised 12%-35% of total variance in seed set and 62% of variance in seed mass, and there was a significant negative environmental covariance between seed set and seed mass. Parental interaction made no detectable contribution to phenotypic variance in either of our measures of postpollination success, although crossing distance did contribute slightly but significantly to fit of the model in some cases. Finally, there was no detectable paternal variance (Vpat ) in seed set or seed mass. These results are in keeping with reports from other studies of natural plant populations. The finding of little or no paternal variance in particular suggests little scope for postpollination sexual selection through the male function of cosexual plants such as I. aggregata.

Hierarchical analysis of allozymic and morphometric variation in a montane herb, Ipomopsis aggregata (Polemoniaceae) - P. G. Wolf; Diane R. Campbell (Journal of Heredity, 1995)

A comparative study: water chemistry, species richness and abundance in freshwater springs of Gunnison County - A. Hultgren; B. Roe; K. Krakauer; M. Arreguin; B. L. Morrison (1995)

Sackungen at the Aspen Highlands Ski Area, Pitkin County, Colorado - J. R. IRVINE; J. P. McCALPIN (Environmental & Engineering Geoscience, 1995)
Research Article| January 01, 1995 Sackungen at the Aspen Highlands Ski Area, Pitkin County, Colorado JAMES P. McCALPIN; JAMES P. McCALPIN GEO-HAZ Consulting, Inc., P. O. Box 1377, Estes Park, CO 80517 Search for other works by this author on: GSW Google Scholar JAMES R. IRVINE JAMES R. IRVINE Consulting Soil Scientist 182 County Road 24, Ridgway, CO 81432 Search for other works by this author on: GSW Google Scholar Environmental & Engineering Geoscience (1995) I (3): 277–290. https://doi.org/10.2113/gseegeosci.I.3.277 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation JAMES P. McCALPIN, JAMES R. IRVINE; Sackungen at the Aspen Highlands Ski Area, Pitkin County, Colorado. Environmental & Engineering Geoscience 1995;; I (3): 277–290. doi: https://doi.org/10.2113/gseegeosci.I.3.277 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Numerous linear geomorphic features of suspected gravitational spreading origin, collectively termed sackungen, occur at elevations of 3,475–3,775 m at the head of the Aspen Highlands Ski Area near Aspen, Colorado. Features include double-crested ridges, upslope-facing scarps, linear troughs, and downslope-facing scarps. Most features are aligned with the prominent joint set (strike N25°–45°E, dip 80°–90° NW) that parallels the flanking, 1,150-m deep U-shaped glacial valleys of Castle and Maroon creeks. A backhoe trench 6 m long and 2 m deep was excavated across an upslope-facing scarp and adjacent trough to reveal the style and age of surface deformation. Sandstone bedrock of the Maroon Formation was extensively fractured under the scarp face, with abundant dilational voids. Hillslope colluvium was truncated at the main sackung fault plane, and was overlain by up to 1.2 m of fine-grained sag pond sediments. Seven buried soils were present in the trough fill, composed of A, and E or Bw horizons; A horizons at 35 cm, 84 cm, and 98 cm below the surface yield uncorrected 14C ages of 3060+150, 6290+70, and 7910+80 14C yrs B.P., respectively. Extrapolation of deposition rates to the base of the fill indicates that the trough formed ca. 11–11.5 ka, several thousand years after glacial ice had melted from the flanking glacial valleys. Trench stratigraphy suggests that slow vertical offset across the trough has continued since 11 ka, at rates of 0.14–0.75 mm/yr, perhaps accompanied by horizontal spreading at 0.43 mm/yr in the past 3 ka. This rate of spreading is slower than the 1–5 mm/yr measured by Varnes and others (1990) across sackungen in the Sawatch Range to the east, but still constitutes a constraint on foundation design for buildings and lift towers. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Size and abundance: breeding population density of the Calliope Hummingbird - L. L. Calder; W. A. Calder (Auk, 1995)
BENT, A. C. 1942. Life histories of North American flycatchers, larks, swallows and their allies. U.S. Natl. Mus. Bull. 179. BUDD, L. F., R. B. AREND, J. W. HURST, AND V. H. ANDERSON. 1979. Fort Bliss environmental analysis and impact assessment. Photographic Interpretation Corporation, Hanover, New Hampshire. BUTLER, R. W. 1980. Appropriation of an American Robin nest by Dark-eyed Juncos. Can. Field Nat. 94:197. BUTLER, R. W., AND C. A. CAMPBELL. 1987. Nest appropriation and interspecific feeding between Tree Swallows, Tachycineta bicolor, and Barn Swallows, Hirundo rustica. Can. Field-Nat. 101:433-434. EHRLICH, P. R., D. S. DOBKIN, AND D. WHEYE. 1988. The birder's handbook. Simon and Schuster, New York. EMLEN, S. T., AND S. L. VEHRENCAMP. 1983. Cooperative breeding strategies among birds. Pages 93-120 in Perspectives in ornithology (A. H. Brush and G. A. Clark, Jr., Eds.). Cambridge Univ. Press, Cambridge. GIBBONS, D. W. 1986. Brood parasitism and cooperative nesting in the Moorhen, Gallinula chloropus. Behav. Ecol. Sociobiol. 19:221-232. GRZYBOWSKI, J. A. 1979. Responses of Barn Swallows to eggs, young, nests and nest sites. Condor 81: 236-246. KOENIG, W. D., R. L. MUMME, AND F. A. PITELKA. 1984. The breeding system of the Acorn Woodpecker in central coastal California. Z. Tierpsychol. 65: 289-308. SHIELDS, W. M. 1984. Barn Swallow mobbing: Selfdefence, collateral kin defence, group defence, or parental care? Anim. Behav. 32:132-148. SHIELDS, W. M., J. R. CROOK, M. L. HEBBLETHWAITE, AND S. S. WILES-EHMANN. 1988. Ideal free coloniality in the swallows. Pages 189-228 in The ecology of social behavior (C. N. Slobodchikoff, Ed.). Academic Press, Orlando, Florida. SHREVE, F. 1942. The desert vegetation of North America. Bot. Rev. 8:195-246. TERRES, J. K. 1991. The Audubon Society encyclopedia of North American birds. Wings Books, New York.

Status of Mustela frenata in the Gothic area - T. Tanner (1995)

Predatory and parasitic Lepidoptera: carnivores living on plants - N. E. Pierce (Journal of the Lepidoptera Society, 1995)

The effect of sediment load on aquatic invertebrate diversity in beaver ponds - I. Behrens (1995)

Correlation of environmental parameters and insect abundance to bat foraging patterns - M. E. P. Vieira (1995)

Harvest rates and escape speeds in two coexisting species of montane ground squirrels - Richard Alexander Smith (Journal of Mammalogy, 1995)
I measured harvest rates and maximum running-escape speeds of two species of ground-dwelling squirrels, the least chipmunk (Tamias minimus) and the golden-mantled ground squirrel (Spermophilus lateralis). Using seed trays in which foragers experienced diminishing returns, I found that S. lateralis harvested seeds faster than did T. minimus. This difference was due to a significantly higher rate of encounter of seeds by S. lateralis. There was no significant difference in handling times between species. Higher harvest rates may reduce predation risk by decreasing the amount of time spent exposed to predators while foraging. I also measured maximum running speeds by chasing animals over short distances. I found that S. lateralis ran significantly faster than did T. minimus (3.14 and 2.13 m/s, respectively). A faster maximum running speed could enable S. lateralis to escape pursuit, but also to exploit the meadow habitat farther from the safety of the forested edge. In previous studies, I found that T. minimus perceived a greater level of predation risk than did S. lateralis in areas 20 m from protective cover and that they were competitively inferior there. The results from this study provide a possible mechanism for this difference. One generalization from this study is that, if larger body size usually confers an anti-predator advantage, larger-bodied species should more often exploit riskier (often open) habitats.

Colorado Mathematical Olympiad: The first 10 years and further explorations, by Alexander Soifer. Pp 188. $19.95. 1994. ISBN 0- 940263-03-3 (Center for Excellence in Mathematical Education, 855 Red Mesa Drive, Colorado Springs CO80906, USA) - Steve Abbott (The Mathematical Gazette, 1995)
Colorado Mathematical Olympiad: The first 10 years and further explorations, by Alexander Soifer. Pp 188. $19.95. 1994. ISBN 0- 940263-03-3 (Center for Excellence in Mathematical Education, 855 Red Mesa Drive, Colorado Springs CO80906, USA) - Volume 79 Issue 484

Hydrological effects of hypothetical climate change in the East River basin, Colorado, USA - Lauren E. Hay; Gregory J. McCabe (Hydrological Sciences Journal, 1995)
Abstract In 1988, the US Geological Survey began a study of the effects of potential climate change on the water resources of the Gunnison River basin. The Gunnison River, in southwestern Colorado, is an important tributary of the Colorado River, contributing approximately 40% of the flow of the Colorado River at the Colorado/Utah stateline. As part of the study, the sensitivity of annual and seasonal runoff in the East River basin, a sub-basin of the Gunnison River basin, to changes in temperature and precipitation was examined. To perform the sensitivity analyses, hypothetical climate changes were used to alter current time series of temperature and precipitation. The altered time series were then used as inputs to a hydrological model that translated these inputs into estimates of runoff. Mean annual and seasonal runoff resulting from a range of hypothetical climate changes were compared and evaluated. Results indicated that in general, changes in precipitation had a larger effect on changes in runoff than did changes in temperature. Changes in precipitation had significant effects on runoff during all seasons. Changes in temperature primarily affected the temporal distribution of runoff through the year. Changes in temperature affected the timing of snowmelt and the ratio of rain to snow, and therefore the effects of temperature were particularly significant during the spring and summer seasons. On an annual basis, increases in temperature led only to slight decreases in runoff. Results also indicated that the effects of an increase in mean annual temperature of 4°C on annual runoff could be offset by an increase in annual precipitation of between 4 and 5%, and that the magnitude of natural climatic variability was large and might mask the effects of long term climate changes.

Impacts of recreational boating on freshwater invertebrates - J. L. Hayes (1995)

Hierarchical Analysis of Allozymic and Morphometric variation in a Montane Herb, Ipomopsis Aggregata - P. G. Wolf; Diane R. Campbell (Journal of Heredity, 1995)

A new horizon for biological field stations and marine laboratories (1995)

Seed dispersal in Erythronium grandiflorum (Liliaceae) - G. D. Weiblen; James D. Thomson (Oecologia, 1995)
The lack of a special seed dispersal mechanism in E. grandiflorum is discussed in terms of a source-sink model for seedling establishment with respect to distance from the parental plants, which yields a more complete estimate of Wright's neighborhood size, Ne.

Reproductive energetics of adult male yellow-bellied marmots (Marmota flaviventris) - C. M. Salsbury; Kenneth B. Armitage (Canadian Journal of Zoology, 1995)
We examined the energy expenditure of adult male yellow-bellied marmots (Marmota flaviventris) and its relationship to various female-defense characteristics critical to male reproductive success. Resting metabolic rates of males were estimated in the laboratory via oxygen-consumption analysis, and field metabolic rates were estimated using a doubly labeled water technique. Male home-range size, number of females defended by males, dispersion of females in the habitat, and date into the active season were considered to be predictors of male energy expenditure in excess of maintenance costs (field metabolic rate minus resting metabolic rate). Energy expenditure was best explained by a defensibility index based on the number and dispersion of females defended; expenditure increased with number and dispersion of females. Energy expenditure increased with date into the active season. Environmental constraints on male activity during the mating season may have led to a shift in male reproductive investment to later in the season, when intruder pressure by conspecifics increased. No short-term survival costs were associated with high energy expenditure; males appeared to engage in reproductive behaviors congruent with their physiological capabilities.

An exploration of the effects of ant-aphid interaction on host plant growth - E. K. Jewett (1995)

Surveying beavers around RMBL and how effective are beaver ponds as sediment traps - I. Behrens (1995)

Facultative polygyny in the ant Myrmica tahoensis - J. D. Evans (1995)

Selection on flower color in an Ipomopsis hybrid zone - E. J. Melendez (1995)

An investigation of the effects of pH, aluminum precipitate, and periphyton densities on benthic invertebrate populations in Paradise Basin, Colorado - S. L. Feldhousen (1995)

Estimates of mayfly mortality: is stonefly predation a significant source? - B. L. Kerans; C. G. Anderson; B. L. Peckarsky (Oikos, 1995)
Kerans, B. L., Peckarsky, B. L. and Anderson, C. 1995. Estimates of mayfly mortality: is stonefly predation a significant source? - Oikos 74: 315-323. Field experiments and surveys were canied out in a Rocky Mountain alpine stream during the summers of 1990 and 1992 to estimate the proportion of natural losses of the mayfly Baetis bicaudatus resulting from the co-occurring, predatory stonefly, Kogotus modestus. Functional response experiments determined the number of prey consumed by male and female Kogotus by manipulating the densities of prey and the presence or absence of predators in stream-side chambers. Estimates of losses of Baetis and density of Kogotus were based on ten benthic samples collected weekly (except for last sampling date) from one study reach. Concurrently, drift density of Baetis was estimated upstream and downstream of the reach to determine gains or losses of Baetis resulting from migration. In the functional response experiments Kogotus consumed the same number of prey regardless of prey densities. Female predators tended to consume more prey (- 2 d-I) than males (- 1 d-I), although the result was only statistically significant in one out of three experiments. Per-capita mortality rates of Baetis declined from 0.01 to 0.001 d-' (predator m-?)-' with increasing prey density. In the study reach Baetis density declined 70% during the 4.5 wk and per-capita losses averaged 3.8% d-I. We estimated that predation by Kogotus could cause between 1.6 and 9.5% of the losses of Baetis from the study reach. This occurred because high losses of Baetis were combined with low consumption rates and densities (1.83 individuals m-') of Kogotus. Baetis drift density was higher at night than during the day. Drift densities of Baetis tended to be higher leaving than entering the reach in nighttime estimates, although the results were not statistically signficant. Few replicates resulted in low power to detect differences in upstream and downstream drift densities; therefore, it is possible that some losses could be the result of drift out of the study reach. Nonetheless our results suggest that Kogotus populations had little direct, lethal effect on Baetis populations in this study reach.

Exploitation of lycaenid-ant mutualisms by braconid parasitoids - P. Seufort; K. Fiedler; T. Baumgarten; J. G. Pearson; N. E. Pierce (Journal of Research on the Lepidoptera, 1995)
Larvae of 17 Lycaenidae butterfly species from Europe, North America, South East Asia and Australia were observed to retain at least some of their adaptations related to myrmecophily even after parasitic braconid larvae have emerged from them. The myrmecophilous glandular organs and vibratory muscles of such larval carcasses remain functional for up to 8 days. The cuticle of lycaenid larvae contains extractable "adoption substances" which elicit antennal drumming in their tending ants. These adoption substances, as well, appear to persist in a functional state beyond parasitoid emergence, and the larval carcasses are hence tended much like healthy caterpillars. In all examples, the braconids may receive selective advantages through myrmecophily of their host larvae, instead of being suppressed by the ant guard. Interactions where parasitoids exploit the ant-mutualism of their lycaenid hosts have as yet been recorded only from the Apanteles group in the Braconidae-Microgasterinae .

Ecological restoration through behavioral change - Jessica D. Pratt; J. Cairns (Restoration Ecology, 1995)

Structure-activity relationships of norditerpenoid alkaloids occurring in toxic larkspur Delphinium species - K. E. Panter; G. D. Manners; S. W. Pelletier (Journal of Natural Products, 1995)

The reproductive outputs of Delphinium nelsonii at differing elevations - J. Schiller (1995)

Carcass selection in a high altitude population of the burying beetle, Nicrophorus investigator, (Silphidae) - B. Heese; Richard Alexander Smith (Southwestern Naturalist, 1995)

Microhabitat and activity periodicity of predatory stoneflies and their mayfly prey in a western Colorado stream - C. A. Cowan; B. L. Peckarsky (Oikos, 1995)
Experiments were conducted to determine whether overlap between microhabitat preferences and activity periodicities of four mayfly species and their stonefly predators could explain species-specific differences in predator-prey encounter frequencies. Preferences for rock type (slate or granite), flow microhabitat (high or low), rock surface (top, bottom, upstream or downstream sides), and periodicity of drift and the use of rock tops were measured in a stream-side system of flow-through circular Plexiglas chambers receiving natural stream water and light levels. These parameters were compared among the predatory stoneflies, Megarcys signata or Kogotus modestus, and four species of mayflies that vary in their encounter rates with the stoneflies. Based on predator-prey encounter rates previously observed in similar chambers, we expected greater overlap between Megarcys and Ephemerella infrequens and the overwintering generation of the bivoltine mayfly, Baetis bicaudatus than with Cinygmula sp. Likewise, we expected Kogotus microhabitat use to overlap more strongly with that of summer generation Baetis than with later instars of Cinygmula and Epeorus deceptivus. Results ran counter to our predictions, indicating that microhabitats of the prey species with high predator encounter rates did not overlap more strongly with the stoneflies than did mayflies with low predator encounter rates. Most mayflies and stoneflies preferred the bottom surfaces of granite rocks, and showed few flow preferences. Most were nocturnal in their use of top rock surfaces, in drift and feeding activity periodicity. Therefore, nocturnal activity periodicities of both mayflies and stoneflies confirm that mayflies have not evolved feeding periodicity to avoid encounters with foraging stonefly predators. We conclude therefore, that neither temporal nor spatial microhabitat overlap is a reasonable explanation of differential encounter rates between predatory stoneflies and their mayfly prey. Alternative explanations for differential encounter rates are that more abundant or more mobile mayflies have higher encounter rates with predators, and effective pre-contact predator avoidance responses of other mayflies reduce their encounter rates with stoneflies.

Management of mule deer in edge habitats - R. Crafts (1995)

Costs and benefits of sociality in yellow-bellied marmots (Marmota flaviventris): do noncolonial females have lower fitness? (1995)

Postfertilization causes of differential success of pollen donors in Erythronium grandiflorum (Liliaceae): Nonrandom ovule abortion - L. P. Rigney (American Journal of Botany, 1995)

Floral sex allocation in sequentially blooming plants - D. Charlesworth; J. Brunet (Evolution, 1995)
In plants whose flowers develop in a sequence, different flowers may exhibit temporal variation in pollen donation and receipt such that the fitness contributions through male and female functions can vary among flowers. Dichogamy, or directional pollinator movements within inflorescences, can create situations where flowers in different stages in the sequence may differ in the numbers of flowers in the female stage available as potential mates. We present an evolutionarily stable strategy (ESS) analysis of the resource allocations expected in different flowers in hermaphroditic plants when the mating environments vary among flowers. This introduces a modular element into sex-allocation models. Our analysis shows that such variation in the mating environments of flowers can select for differences in sex allocation between flowers. When male and female fertilities are nonlinear functions of the allocations, variation in resource availability can also select for variation in sex allocation among flowers. The influence of dichogamy and pollinator directionality on floral sex allocation is discussed, and the empirical evidence supporting the predictions derived from the model is briefly reviewed. The implications of our results for the evolution of andromonoecy and monoecy are discussed.

Pollinator effectiveness of Mertensia fusiformis, Delphinium nelsonii, and D. barbeyii: is there one best pollinator to which the plant is adapted? - J. J. Gannon (1995)

Effects of avalanche intensity on Populus tremuloides density - L. P. Hoover (1995)

Oviposition preferences in the sharp-veined white butterfly, Pieris napi - V. Ezenwa (1995)

Lichen diversity in aspen edge and spruce-fir edge - K. D. Craig (1995)

Tests of pollen viability in hand-pollination experiments: a literature review - J. Stone; S. Dent-Acosta; James D. Thomson (American Journal of Botany, 1995)

Plant community structure as a function of grazing by cattle - M. Trout (1995)

An assessment of the abundance and habitat requirements of the southern red-backed vole, Clethrionomys gapperi on Snodgrass Mountain - A. Benson (1994)

Home-range size and exploratory excursions of adult, male yellow-bellied marmots - C. M. Salsbury; Kenneth B. Armitage (Journal of Mammalogy, 1994)
Home-range sizes of adult, male yellow-bellied marmots (Marmota flaviventris) were estimated from radiotelemetry, trapping, and visual observation. Home ranges were monitored from early May to late August in 1989, 1990, and 1991. Home-range size varied greatly among males (range, 0.06–47.51 ha). Median home-range size for all males was 1.02 ha, larger than previous estimates for the species. Distribution of females and localized fluctuations in density of males influenced home-range size of males. Home-range size was not related to number of females defended or to body mass of males. Several males made excursions from their home ranges, perhaps to locate additional mates. These results indicate that male marmots behaviorally respond to the density and distribution of females.

A comparison of several lake eutrophication restorative techniques - A. Prussian (1994)

The effect of inflorescence number on bee behavior in Delphinium barbeyi - J. Ruvinsky (1994)

Benefits of restoration on abandoned roads at high altitude: minimizing the impacts of habitat fragmentation - J. F. Burkhart (1994)

Elevational variation of quinolizidine alkaloid contents in a lupine (Lupinus argentus) of the Rocky Mountains - M. Wink; D. B. Carey (Journal of Chemical Ecology, 1994)

Biodiversity of aspen (Populus tremuloides) groves: a precursor to studies of ecosystem services - E. L. Catanese; John M. Hughes (1994)

The Gothic earthflow revisited: a chronosequence examination of colonization on a subalpine earthflow - C. G. Curtin (Vegetatio, 1994)
A chronosequence study of permanent plots spanning 45 years on a 70-year-old subalpine earthflow in south-western Colorado suggests that it is the severe microclimate of the earthflow which is limiting further colonization of the site.

Crossing distance effects in Delphinium nelsonii: outbreeding and inbreeding depression in progeny fitness - Mary V. Price; Nickolas M. Waser (Evolution, 1994)

Pollen viability, vigor, and competitive ability in Erythronium grandiflorum (Liliaceae) - K. M. Karoly; L. P. Rigney; B. A. Thomson; James D. Thomson (American Journal of Botany, 1994)

Evolution of alternative life histories in the tiger salamander, Ambystoma tigrinum nebulosum - Howard Whiteman (1994)

Niche separation in the foraging of tree swallows (Tachycineta bicolor) and violet-green swallows (Tachycineta thalassina) - P. Wright (1994)

Social behavior of ants in the genus Myrmica: occurrence of worker specialization and survivorship implications - A. C. Valdez (1994)

The generation of nuclear waste: are there alternatives? - S. Southard (1994)

Pollinator restriction in the narrow-tube flower type of Mertensia ciliata (James) G. Don (Boraginaceae) - K. Suzuki (Plant Species Biology, 1994)

Diet alters metabolic rate in the yellow-bellied marmot during hibernation. - P. K. Ram; C. R. Thorp; G. L. Florant (Physiological Zoology, 1994)

Actual Problems of Marmots [sic] Investigation (1994)

Behavioral responses to predation risk: survival strategies of the golden-mantled ground squirrel - R. L. Carnevale (1994)

The use and abuse of pollinators by fungi - B. A. Roy (Trends in Ecology and Evolution, 1994)
Recent research shows that fungal exploitation of pollinators has the potential to affect floral evolution, pollination ecology, plant life history traits, as well as disease-transmission dynamics and fungal evolution.

East River water usage problems: effects of current and proposed management practices - J. Renfrow (1994)

Evolution of Facultative Paedomorphosis in Salamanders - Howard Whiteman (Quarterly Review of Biology, 1994)
In some salamander species the retention of larval characteristics in sexually mature adults (paedomorphosis) is an alternative to metamorphosis. In many species paedomorphosis is facultative, thus offering a unique opportunity to test predictions on the evolution of life history variation. Here I expand upon a previous hypothesis ("paedomorph advantage") and present two alternative selection mechanisms ("best of a bad lot" and "dimorphic paedomorph" hypotheses) for the maintenance of facultative paedomorphosis. Each hypothesis makes specific predictions regarding the environmental conditions favoring paedomorphosis, the resulting larval growth patterns, and the fitness consequences to each morph. I evaluate each hypothesis by testing these predictions using published data. No study has conclusively determined the relative fitness of paedomorphs and metamorphs, which limits our understanding of the evolution of this polymorphism. Larval growth patterns suggest, however, that both the paedomorph advantage and the best of a bad lot hypotheses are viable alternatives for the evolutionary maintenance of facultative paedomorphosis in different species. Thus current data on facultative paedomorphosis support the premise that selection can favor the production of an environmentally induced polymorphism through more than one mechanism.

Recommendation for the restoration of the East River bridge site, Gothic, Colorado - D. H. Morris (1994)

Temperate region interactions between ants and Penstemon strictus - J. Pasewalk (1994)

Oviposition behavior of the white cabbage butterfly, Pieris napi, on native and exotic crucifers - K. N. White (1994)

Resting and field metabolic rates of adult male yellow-bellied marmots, Marmota flaviventris - C. M. Salsbury; Kenneth B. Armitage (Comparative Biochemistry and Physiology, 1994)
Total RMR and field metabolic rate of wild-caught males were estimated from oxygen consumption and the doubly-labeled water method and neither total RMR nor specific FMR were significantly related to time.

Foraging site preferences of rufous and broad-tailed hummingbirds - K. Norton (1994)

Allozymes in evolutionary genetics: self-imposed burden or extraordinary tool? - W. B. Watt (Genetics, 1994)

Everyday is restoration day - E. MacDonald (1994)

Bug It: Factoring in Insect Fauna in Ecological Restoration - R. L. Carnevale (1994)

Consequences and plasticity of the specialized predatory behavior of stream-dwelling stonefly larvae - C. A. Cowan; C. G. Anderson; B. L. Peckarsky (Ecology, 1994)
The purpose of this study was to determine experimentally the potential mechanism(s) favoring specialized foraging behavior of stream—dwelling predatory stonefly larvae (Megarcys signata), and whether this specialized behavior was fixed or flexible. We measured stonefly growth rates after 10 d of conditioning on Baetis bicaudatus (Ephemeroptera) or one of two alternative mayfly prey species in replicated circular plexiglass flow—through chambers powered by water from a stream in western Colorado. We then compared attacks per encounter (as an index of predator choice) of conditioned stoneflies to those of unconditioned controls given equal densities of all three prey types. We conducted additional behavioral observations to determine whether predators differentially encountered the alternative prey types on natural substrates, and to determine whether predator—prey microhabitat overlap was mechanism explaining differential prey encounter rates among prey species. Megarcys exhibited a stereotyped attack bias toward swimming mayflies, such as Baetis, following the simple rule, "attack any prey that swim," which results in Megarcys' selection of prey types that swim in response to stonefly encounters. This behavior remained unmodified after extended experience with alternate but palatable nonswimming mayfly species. A potential fitness advantage (measured as relative growth rate) of this behavioral specialization occurred for female Megarcys, but not for males. Female Megarcys grew faster on Baetis diets because they ate more Baetis, not because Baetis was a more intrinsically profitable prey item (in terms of promoting predator growth). Further, high feeding rates on Baetis were a result of disproportionately high encounter rates and attacks per encounter with Baetis compared to the other mayfly species. Our data are consistent with the hypothesis that this predatory behavior arose and is maintained in female stoneflies due to a fitness advantage to individuals specializing on a relatively abundant, easily recognized prey resource. We speculate that this specialized behavior has not been lost in male stoneflies, for which we did not measure a fitness advantage, because there is no strong selection pressure against it. Effective pre—and—post—contact prey defenses may exert enough selection pressure to prevent stoneflies from evolving on alternative mayfly types.

A study of Clethrionomys gapperi habitat preference on Snodgrass - S. Advani (1994)

Beyond floral Batemania: sexual selection on pollination success - M. L. Stanton; L. P. Rigney; P. T. Wilson; P. T. Wilson; James D. Thomson; James D. Thomson (American Naturalist, 1994)

Categorization of food types enhances foraging performance of bumble bees - R. Dukas; Nickolas M. Waser (Animal Behaviour, 1994)

Diapause and the host plant affiliations of lycaenid butterflies - D. B. Carey (Oikos, 1994)
Results of three years of study on the host plant affiliations of two lycaenid butterfly species (Lycaenidae) suggest that differences between the two butterflies in host plant range, plant tissue oviposited on by adults and consumed by larvae, larval growth rates, and adult flight season may be consequences of a difference in diapause stage: one species diapauses as a pupa; the other as a larva. The experimental results and logic leading to this conclusion are summarized. The generality of the correlation between diapause stage and host plant relations are tested through a survey of North American and British lycaenids. Significant relatonships are found. Egg-diapausing species tend to utilize woody hosts and be univoltine. Host range is intermediate. Larval-diapausing species utilize leaves of herbaceous plants and have narrow host ranges

Missed opportunity cost for foraging in Tamias minimus, the least chipmunk, and Spermophilus lateralus, the golden-mantled ground squirrel - R. E. Collins (1994)

Survival of dispersing and philopatric yellow-bellied marmots: what is the cost of dispersal? - D. H. Van Vuren; Kenneth B. Armitage (Oikos, 1994)
Understanding the evolution of dispersal has been hindered by a lack of reliable measures of the cost of dispersal. We report that survival of dispersing yellow-bellied marmots (Marmota flaviventris) (0.73) was only 16% less than survival of philopatric marmots (0.87). A cost-benefit analysis reveals that the survival cost of dispersal may be less than some other costs of philopatry; thus, dispersal is explicable as a tactic to improve individual fitness

Seasonal movement patterns in a subalpine population of the tiger salamander, Ambystoma tigrinum nebulosum - A. J. Bohonak; Howard Whiteman; S. A. Wissinger (Canadian Journal of Zoology, 1994)
Seasonal movements of a subalpine population of metamorphic tiger salamanders, Ambystoma tigrinum nebulosum, were explored from 1990 to 1992. Metamorphic adults bred in permanent and semipermanent habitats during June of each year. After breeding, soma individuals returned to the terrestrial environment, but many remained and congregated in nonpermanent ponds. Metamorphic adults in nonpermanent ponds included those that moved from permanent ponds, those that bred and remained in semipermanent ponds, and those that did not breed but migrated from the terrestrial environment after the breeding season. Dietary analyses indicated that metamorphic adults in nonpermanent ponds have significantly greater numbers, biomass, and calories of prey in their gut than the few metamorphic adults remaining in permanent ponds. This difference was due to the presence of fairy shrimp (Branchinecta coloradensis), which composed 91 % of metamorphic adult diets in nonpermanent ponds and accounted for three times the average caloric value of all prey in gut samples from metamorphic adults in permanent ponds. Intraspecific competition also may have contributed to movement into nonpermanent ponds: post-breeding densities of metamorphic adults in permanent ponds were inversely related to the densities of other morphs (paedo-morphic adults and large larvae). We conclude that metamorphic A. t. nebulosum in this population utilize nonpermanent ponds after the breeding season because of the abundance of high-quality aquatic prey and reduced competition from con-specific morphs.

The effects of light intensity on the activity of predacious stonefly nymphs on mayfly nymphs - C. Lake (1994)

The effects of cattle grazing intensity on riparian environments - M. Pollack (1994)

Fly pollination of Linum lewisii (Linaceae) - C. A. Kearns; David W. Inouye (American Journal of Botany, 1994)

Genetic variation in Penstemon strictus: effects of island habitats - J. Pasewalk (1994)

The relationship between stream velocity and body size of Blephariceridae larvae - the net-winged midge - J. V. Peck (1994)

The effects of pathogen-induced pseudoflowers and buttercups on each other's insect visitation - B. A. Roy (Ecology, 1994)
Pseudoflowers induced by the rust fungus Puccinia monoica on Arabis spp. are flower—like in color, shape, size, nectar production, and scent. Pseudoflowers attract insects that aid the rust's reproduction in a way that is analogous to pollination in flowering plants. I explored the effects of pathogen—induced pseudoflowers and co—blooming buttercups (Ranunculus inamoenus) on each other's insect visitation by comparing visitation in single—species plots and mixtures. Visitation to pseudoflowers was greater in mixtures containing buttercups than in pseudoflowers plots of the same density, and visitation to buttercups was also greater in the mixtures than in pure buttercup plots. Because fungal pseudoflowers and buttercups both appeared to receive greater visitation when associated with each other than when alone, and both species produce food for insect visitors, this interaction could be described as Mullerian floral mimicry. However, several characteristics of this system do not fit standard definitions of mimicry: (1) pseudoflowers are not necessarily mimicking any particular species but instead may be generalized flower—mimics, (2) flower visitors may not always mistake pseudoflowers for flowers but may actually choose them, and (3) under some circumstances pseudoflowers and flowers may compete for visitors. Competition in favor of pseudoflowers is most likely when flies are the primary flower visitors or on the rare occasions when pseudoflowers are common relative to other species.

Diel feeding and positioning periodicity of a grazing mayfly in a trout stream and a fishless stream - C. A. Cowan; B. L. Peckarsky (Canadian Journal of Fisheries and Aquatic Science, 1994)
We studied the feeding and positioning periodicity on natural substrates of the overwintering and fast-growing summer generations of a grazing mayfly, Baetis bicaudatus, in a third-order trout stream and a fishless, first-order tributary in western Colorado. At 4-h intervals over 24-h, we recorded the number of Baetis on stone tops in flow-through enclosures in situ and in streamside circular flow-through chambers. We determined the feeding periodicity of Baetis using abundance of plant pigments as an index of gut fullness. Baetis were nocturnal in the trout stream; more animals were found on stone tops and guts were fuller at night, suggesting that individuals came to stone tops to feed during darkness. However, Baetis from the fishless stream were either aperiodic or weakly nocturnal. We tested the hypothesis that nocturnal feeding by Baetis is a response to the presence of visually feeding trout by conducting transplant experiments in the circular streams. After 24 h, Baetis transferred from the trout stream to fishless water remained strongly nocturnal, while Baetis transferred from the fishless stream to trout water became significantly more nocturnal, suggesting that the risk of fish predation outweighs the benefits of relaxing nocturnal periodicity to feed continuously.

The effect of pH and other pollutants on benthic invertebrates in a pristine alpine watershed in central Colorado - G. L. Rouse (1994)

An investigation of the structure and location of escape burrows for the ground squirrel Tamias minimus - D. E. Carter (1994)

Beyond floral Batemania: sexual selection on pollination success (American Naturalist, 1994)

Geological hazards, vulnerability, and risk assessment using GIS: model for Glenwood Springs, Colorado - Mario Mejía-Navarro; Ellen Wohl; Sherry Oaks (Elsevier eBooks, 1994)

Spatial navigation in natural habitats by ground-dwelling sciurids - L. D. Devenport; J. A. Devenport (Animal Behaviour, 1994)

Mining for bats: a study of the mine usage of bats at the Avery Mine - P. D. Mariner (1994)

Effects of pumping on the East River - J. Renfrow (1994)

Bumblebee foraging behavior: the roles of floral scent and color - Eric A. Odell (1994)

When do hummingbirds use torpor in nature? - W. A. Calder (Physiological Zoology, 1994)
The physiology of torpor in hummingbirds is well known from laboratory studies, but we still do not know when or how often this means of energy conservation is used in nature, whether regularly (the "routine" hypothesis) or only in response to inadequate food intake (the "emergency-only" hypothesis). I used body masses of broad-tailed hummingbirds (Selasphorus platycercus) to evaluate these hypotheses. Wild birds were weighed on electronic balances (1) on capture in mist-nets or traps and (2) when perched at feeders containing sucrose solutions. Masses followed predictable patterns within a season (breeding or wintering). Estimated energy equivalents of daily cycles of storage and depletion did not support the routine hypothesis. Converted to energy equivalent after adjusting for water content of dusk feeding, the estimated energy equivalent of overnight mass decrease (adjusted for water content of dusk feeding) averaged 15 times the demand for torpor during the breeding season, normally equalling or exceeding the demand for high nocturnal body temperature. In the annual cycle of the broadtail, the times when torpor might become necessary are (1) on arrival at breeding or wintering sites before flowers are abundant and (2) in midseasons (when nectar production fails), when daytime feeding is interrupted by storms, or when birds are otherwise prevented from storing adequate reserves by dusk.

Vegetation and tree abundance at active and non-active beaver ponds - E. MacDonald (1994)

An intra- and inter-species investigation of burrow distances between Spermophilus lateralis and Tamias minimus - D. E. Carter (1994)

Variability of quinolizidine alkaloid profiles of Lupinus argenteus (Fabaceae) from North America - M. Wink; D. B. Carey (Biochemical Systematics and Ecology, 1994)

Through the 'Scope: An Occurrence of Prehnite in the Red Mountain Mining District Ouray County, Colorado - Tom Rosemeyer (Rocks & Minerals, 1994)

You can't go home again: effects of an avalanche barrier on small rodent homing - K. Mockler (1994)

The activity patterns of the long-legged bat, Myotis volans in conjunction with habitat - A. Hines (1994)

Effects of floral traits, pollinator visitation, and plant size on Ipomopsis aggregata fruit production - Richard S. Mitchell (American Naturalist, 1994)
Current understanding of reproduction for animal-pollinated plant species is based on the premise that traits of flowers and inflorescences influence reproductive success by affecting pollinator behavior. This implies that within-population variation in such traits should affect reproductive success. I used path analysis and structural equation modeling to test this hypothesis for two populations of the monocarpic herb Ipomopsis aggregata (Polemoniaceae). The basic hypothesis proposes that pollinator behavior may be affected by plant traits (including floral nectar production rate, corolla size, number of open flowers, and inflorescence height) and that behavior, along with plant size, may influence reproductive success through female function (proportion fruit set and total fruit production). This hypothesis was consistent with the data in both populations, although the specific details of the appropriate formulation varied. For both populations, the basic hypothesis is significantly better as a description of the interactions than alternative hypotheses that ignore the effects of plant traits on pollinator behavior or plant size on reproduction. In one population, disallowing the effects of pollinator behavior on reproduction significantly decreased the fit of model to data, and in the other, the decrease was almost significant (P = .06). Overall, the fundamental causal relationships proposed in the basic hypothesis were confirmed.

Relationships between atmospheric circulation and snowpack in the Gunnison River basin, Colorado - Gregory J. McCabe (Journal of Hydrology, 1994)

Equality found among ant protectors of Helianthella quinquenervis - S. Southard (1994)

Contributions of Harry Gunnison Brown (1880–1975) - Christopher K. Ryan (Journal of Public Finance and Public Choice, 1994)
Sebbene le opere di Harry Gunnison Brown, prese singolarmente, non siano state trascurate in modo particolare, l’insieme della sua produzione scientifica non è ancora stato oggetto di attento esame. Dopo aver collaborate con Irving Fisher al suo volume sul potere d’acquisto della moneta, Brown pubblicò nel 1914 un libro sul commercio internazionale, nel quale sostenne con vigore il libero scambio. È del 1916 un’importante opera sui criteri per stabilire le tariffe nei trasporti, da lui ricavati basandosi sui loro effetti sul benessere generale. La sua opera più nota è il volume The Economics of Taxation, del 1924, ormai considerate un classico sull’argomento. Un breve scritto del 1939, dedicato all’incidenza di un’imposta generale sulle vendite, ha avuto molto successo a motivo deU’originalità della sua tesi, secondo cui quest’imposta non darebbe luogo ad una diminuzione della produzione e quindi non farebbe aumentare i prezzi. A proposito della Grande Depressione, egli ritenne che una delle sue cause fosse stata l’inadeguatezza delle politiche della Riserva Federale. Il suo atteggiamento nei riguardi del pensiero keynesiano fu parimenti critico. Nel dopoguerra Brown si preoccupò dello sviluppo del debito pubblico, ritenendo che l’eccessivo indebitamento avrebbe reso necessarie maggiori imposte, disincentivando così l’economia. Uno dei temi preferiti da Brown fu quello dell’imposta unica sulla terra, argomento a cui dedicò una lunga serie di studi, che tuttavia non si può dire abbiano contribuito a rafforzare la sua immagine di studioso.

Non-visual communication in freshwater benthos: an overview - S. I. Dodson; L. B. Kats; A. P. Covich; T. A. Crowl; J. N. Culp; B. L. Peckarsky (Journal of the North American Benthological Society, 1994)
This overview of non-visual communication in freshwater benthic animals emphasizes recent studies of the effect of chemical and mechanical signals on predator-prey interactions of benthic macroinvertebrates and amphibians. Prey species use chemical signals to modify their morphological development, life history strategy, feeding, and predator avoidance behavior. The advantages of chemical signals are that they can be used in dark or turbid environments by animals that do not have image-forming eyes. Chemical signals are more persistent than mechanical signals, and they allow species-level identification of predator species. In streams, prey species may use mechanical signals (hydrodynamic pressure waves or sound) to avoid predators approaching from downstream (a situation characteristic of streams and in which chemical signals are unreliable) and to initiate escape responses. Predators often depend on chemical signals to stimulate or inhibit feeding, and they use species-specific mechanical signals to locate or track prey or potential mates. The exact nature of non-visual signals depends on ecological constraints of both the sender and receiver. Responses to non-visual signals may be adapted to local predator conditions. Non-visual signals are effectively used over a wide range of temporal and spatial scales in all aquatic habitats. Organisms often adjust their responses as ontogenic development results in changing size, diet, and habitat.

Exotic plant species along Gothic roadsides - R. E. Collins (1994)

Indirect selection of stigma position in Ipomopsis aggregata via a genetically correlated trait - Mary V. Price; Nickolas M. Waser; Diane R. Campbell (Evolution, 1994)

Reintroduction of endangered species - A. Wojtalik (1994)

Comparison of stonefly habitat on various sized rocks - A. Prussian (1994)

Systematic increase in pollen carryover and its consequences for geitonogamy in plant populations - D. A. Stratton; B. A. Thomson; William Morris; Mary V. Price; James D. Thomson; Nickolas M. Waser (Oikos, 1994)
W. F. Morris, M. V. Price, N. M. Waser, J. D. Thomson, B. Thomson, D. A. Stratton, Systematic Increase in Pollen Carryover and Its Consequences for Geitonogamy in Plant Populations, Oikos, Vol. 71, No. 3 (Dec., 1994), pp. 431-440

Pollen discounting in Erythronium grandiflorum: mass-action estimates from pollen transfer dynamics - Kenneth W. Holsinger; James D. Thomson (American Naturalist, 1994)
Pollen discounting, a reduction in success as an outcross pollen parent as a result of selfing, can reduce or eliminate the reproductive advantage commonly attributed to selfing. Previous estimates of pollen discounting have been based on segregation analysis of progeny from open-pollinated plants. Using data from Erythronium grandiflorum, we illustrate how direct measures of pollen transfer can be used to estimate discounting rates, and we discuss the relationship between absolute discounting rates measured in this way and relative discounting rates measured through segregation analysis. Only about 0.4% of the pollen removed from anthers in E. grandiflorum is used in selfing, and only a little more (0.5%) is delivered to the stigmas of other plants. Using these estimates in the framework of a mass-action model suggests that the success rate of self-pollen is almost 80 times that of outcross pollen. Thus, variants increasing the discounting rate would appear to have a substantial reproductive advantage in E. grandiflorum. Pollen discounting cannot explain the maintenance of an outcrossed mating system in E. grandiflorum, and it may also fail in other plants in which a large proportion of the pollen produced never reaches a receptive stigma.

Actual Problems of Marmots [sic] Investigation - G. E. Gurri-Glass; Kenneth B. Armitage; Kenneth B. Armitage (1994)

The Pending Extinction of the Uncompahgre Fritillary Butterfly - Hugh B. Britten; Dennis D. Murphy; Peter F. Brussard (Conservation Biology, 1994)
Previous mark‐recapture studies and population size estimates indicated that in the 1980s populations of the endangered Uncompahgre fritillary ( Boloria acrocnema ) declined precipitously, apparently leading to extirpation at its type locality. This locality and a nearby second site, both high in the San Juan Mountains of southwestern Colorado, constitute the total known range of B. acrocnema . A survey of 20 presumptive allozyme loci from one B. acrocnema population and seven populations of the closely related B. improba , sampled along the Rocky Mountain cordillera from the Yukon Territory, Canada, to the Wind River Range of Wyoming, revealed that B. acrocnema populations are less variable genetically than are B. improba populations in the northern part of that species’ North American range. Genetic variability was also assayed at 18 presumptive allozyme loci in populations of Boloria titania, which were sampled from five of the same locations for comparison with the B. improba‐B. acrocnema clade. Low estimates of heterozygosity indicate that genetic and demographic factors preceded by historic human disturbance are causing the decline of B. acrocnema . In addition, persistent drought conditions in southwestern Colorado throughout the 1980s probably contributed to the population declines. Conservation recommendations include strict enforcement of the ban against collecting pursuant to the Endangered Species Act, careful monitoring of known B. acrocnema sites, and possible translocations. Extreme measures beyond these will be costly and may be inappropriate for this relict species, which has an unknown capacity to persist in the face of local weather fluctuations and predicted regional warming trends.

Quantitative genetics of sequential life-history and juvenile traits in the partially selfing perennial, Aquilegia caerulea - A. M. Montalvo; R. M. Shaw (Evolution, 1994)
We determined the genetic basis of several traits related to overall fitness of Aquilegia caerulea, a perennial herb of the Rocky Mountains in western North America. To obtain measures of heritability relevant to the evolutionary potential of wild populations, we performed full and partial diallel crosses and studied progeny performance in the field. Based on a joint analysis of two designs with a total of 18 parents and 102 crosses, we detected significant maternal variance for seed mass and emergence time, but this component was negligible for later-expressed traits. Low heritability and evidence that maternal effects on seed mass are largely environmental suggest that in this population there is little evolutionary potential for change in seed mass under conditions experienced during the study. Seed mass varied depending on particular combinations of parents and cross direction. Such an interaction can have several different biological interpretations, including that particular maternal parents selectively provision embryos sired by particular pollen genotypes. Width of the first true leaf after 4 wk of growth and leaf size of juvenile plants at years one and two were significantly heritable and positively genetically correlated. Juvenile survival exhibited significant dominance variance, as expected from evidence of inbreeding depression in this trait. In contrast, for other traits that exhibit inbreeding depression in this population (seed mass and third-year leaf size), dominance variance was negligible.

An eye for an eye: can mitigated wetlands pay the bill? - K. Mockler (1994)

The foraging behavior of Ochotona princeps (pika) and how tis correlates to certain aspects of the central foraging theory - J. E. Keet (1994)

Salamander recruitment in Rockies revisited - E. Hoffman; John Harte (BioScience, 1994)
Journal Article Salamander Recruitment in Rockies Revisited Get access John Harte, John Harte Energy and Resources Group, University of CaliforniaBerkeley, CA 94720 Search for other works by this author on: Oxford Academic Google Scholar Erika Hoffman Erika Hoffman Energy and Resources Group, University of CaliforniaBerkeley, CA 94720 Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 44, Issue 6, June 1994, Page 381, https://doi.org/10.2307/1312358 Published: 01 June 1994

Inbreeding depression and maternal effects on Aquilegia caerulea, a partially selfing plant - A. M. Montalvo (Ecology, 1994)

Mineralogy of a Calc-Silicate Locality near: Genesee Park, Jefferson County, Colorado - Peter J. Modreski; Daniel E. Kile (Rocks & Minerals, 1994)

A tourist profile for the Crested Butte/Gothic area - J. Sims; Eric A. Odell (1994)

Acidification and salamander recruitment - E. Hoffman; John Harte (BioScience, 1994)
Journal Article Acidification and Salamander Recruitment Get access John Harte, John Harte Energy and Resources Group, University of California, Berkeley, CA 94720 Search for other works by this author on: Oxford Academic Google Scholar Erika Hoffman Erika Hoffman Energy and Resources Group, University of California, Berkeley, CA 94720 Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 44, Issue 3, March 1994, Pages 125–126, https://doi.org/10.2307/1312246 Published: 01 March 1994

A comparison of bird populations on Mount Crested Butte and Snodgrass Mountain - J. Chodosh (1994)

Does predation effect abundance and diversity of zooplankton in beaver ponds? - E. L. Brookman (1994)

Time-dependent averaging of foraging information in least chipmunks and golden-mantled ground squirrels - J. A. Devenport; L. D. Devenport (Animal Behaviour, 1994)
Behavioural adaptations to resource variability were examined in field experiments with least chipmunks, Tamias minimus, and golden-mantled ground squirrels and were predicted by a dynamic patch assessment model that weights patch information according to its reliability.