Many specialist herbivores eat foods that are apparently "low-quality". The compensatory benefits of a poor diet may include protection from natural enemies. Several bee lineages specialize on pollen of the plant family Asteraceae, which is known to be a poor-quality food. Here we tested the hypothe

Pollen analogue (fluorescent dye) transfer by Valeriana edulis pollinators from dyed males to surrounding females. See README.txt for column descriptions.

Foreign pollen precedence decreased mean seed set by almost 50%, which is consistent with effects observed in previous experiments and can be explained by the fact that foreign pollen often caused stigma lobes to close together within 1.5–6 h, reducing subsequent receptivity.

(1) The transport of pollen from donor flowers by bumble bees was measured by examining deposition on stigmata of sequences of recipient flowers. The rate of decay of grain deposition was estimated as a measure of pollen carryover. (2) Bombus bifarius was a much less effective pollinator of Erythron

In all of 16 experimental replicates discrimination against albinos was reduced or eliminated after painting, and albino handling times declined toward values for blue-flowered inflorescences, indicating that an inferior nectar guide increases the energetic cost of foraging at albino.

Reciprocal seed transplants suggest that there is fine‐scale adaptation in Colorado populations of the perennial herb Delphinium nelsonii. In four experimental plots, seeds planted within 1 m of the maternal parent produced seedlings that began flowering at a younger age and produced more flowers ov

In bumblebee visits to flowers of Erythronium grandiflorum (Liliaceae), the ratio of self‐ to nonself‐ (“outcross”) pollen grains deposited on the stigma is positively correlated with the degree of stylar exsertion beyond the anthers. Natural populations show substantial, continuous variation in sty

For a brief period in 1981 Bombus appositus queens visited Ipomopsis aggregata, a hummingbird-pollinated species with floral characteristics typical of that pollination syndrome. This behavior was not observed in other years. Despite the fact that Ipomopsis lacks floral features associated with bee

Sympatric plant species can compete for pollination services in several ways. For example, pollinators may move between species and deposit heterospecific pollen on stigmas, which in turn may reduce the efficacy of conspecific pollen. We explored this possibility by determining the effect of Delphin

Pollinators that forage indiscriminately can transfer pollen from one species to another, reducing the amount that reaches conspecific flowers. I present evidence that the presence of another plant species visited by the same pollinators can also reduce pollen dispersal distances and outcrossing. Th

To assess the potential for evolutionary change in blooming time within a population of Polemonium foliosissimum Gray (Polemoniaceae), flowering phenology, seed set and seed predation frequencies of individual plants were monitored from 1977-1981 in the Colorado Rocky Mountains. In only 1 of 4 years

Conditions necessary for intraspecific competition for pollinator service, but not intraspecific competition itself, have previously been reported for a population of Polemonium foliossisimum Gray. As in most recent work of this sort, this conclusion was based, in part, on seed set differentials amo

It was found that the slopes of linear dye carryover functions generally became more shallow as floral variability increased; this led to substantially longer carryover in the treatment with greatest variability, and total amounts of dye transferred did not appear to be sensitive to the degree of va