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 hypothesi

1. Plants interact simultaneously with both mutualists and antagonists. While webs of plant-animal interactions in natural systems can be highly complex, most interactions can be simplified into those that are either direct (mediated through pairwise interactions) or indirect (mediated through third

It is hypothesized that the average rate of nectar production per flower for a population of plants is such than an individual plant which possesses this rate has maximum fitness (i.e., is optimal), and predictions concerning nectarProduction in scarlet gilia, a hummingbird pollinated plant are deve

The movements of hummingbirds between inflorescences of scarlet gilia exhibited the following patterns: Although the hummingbirds appeared to avoid moving to the previous inflorescence, no significant correlation was found between the directions of successive inter-inflorescence movements.

I examined the response of bumblebees to two kinds of spatial variation and two kinds of temporal variation in nectar levels. The spatial variation involved differences in reward value among plant species and differences in nectar availability among patches of flowers of a single species. The tempor

Queen bumblebees (Bombus appositus) leave nectar behind in Delphinium nelsoni flowers with high-standing crops of nectar, and residues predicted by an optimal feeding hypothesis agree with field measurements.

It is suggested that bumblebees foraging for pollen may not perceive revisitations and their associated costs because they do not assess pollen returns on a per plant basis, and energetic-efficiency arguments predicting the pattern of foraging movements among plants may be inappropriate.

The breeding systems and stationary spatial distributions of animal-pollinated flowering plants are consistent with Wright's models and such systems have proved excellent for the study of neighborhood size, because gene dispersal can be estimated directly by measuring pollinator movements and seed d

The extrafloral nectar from involucral bracts of Helianthella quinquenervis has more nonprotein (5) and total (24) amino acids than have been reported for any other extrafloral nectar. Seven to twelve additional unknowns, probably nonprotein amino acids, were also found. The concentrations of amino

The results indicate significant correlations between proboscis length and time spent by bees on flowers, and suggest that bumblebees of short probosc is length prefer and are more efficient on short corolla tubes.

It is suggested that outbreeding depression will often occur on a much finer scale than previously recognised, especially in plants subject to restricted pollen and seed dispersal, and a short outcrossing distance is optimal for Delphinium nelsoni Greene.