PS 29-105 - Bee morphological and behavioral traits predict variation in patterns of pollen transport in a diverse co-flowering community in California.

Background/Question/Methods

Pollination requires the transfer of pollen from male (anthers) to female (stigma) reproductive structures. Pollinators, however, are highly variable in the amount and types of pollen they transfer. Nonetheless, little is known about the drivers of among-species variation in patterns of pollen transport. Pollinator body size, abundance, level of flower generalization and sociality (social vs solitary) have the potential to influence pollen load size and diversity. Evaluating drivers of pollen transport efficiency at the community level is critical for understanding the mediators of pollination success. Here, we identify the physical and behavioral factors that mediate pollen transport. Specifically, we ask if sociality, size, abundance, and level of generalization of bees influence the size and diversity of pollen loads carried. To answer these questions, we collected 742 bees while visiting flowers in co-flowering communities in California during four weeks in May of 2021. The identity of the visited flower was recorded. Pollen loads were sampled by swabbing insect appendages with fuchsin jelly while avoiding the corbiculae. The amount and species of pollen were quantified in a microscope at 40x. We recorded bee identity, average body size (length and width), level of flower generalization, abundance, and sociality (solitary or social).

Results/Conclusions

We identified 97 morphospecies of bees. Average pollen load size ranged from 0 to 1274 and the total number of pollen types from 1 to 33 among bee species. Preliminary data suggests that pollen load size and diversity are strongly affected by bee body size. Specifically, both pollen load size and diversity significantly increase with increasing bee body size (length x width). As expected, an increase in flower generalization leads to more diverse pollen loads carried by bees. Interestingly, an increase in flower generalization also leads to a decrease on the average number of pollen types carried by individuals within a species. This might suggest higher specialization in individuals with increasing breadth of resources used per species. Furthermore, more abundant species tend to carry larger and more diverse pollen loads and social bees carried larger pollen loads on average. Our preliminary data highlights wide variation in patterns of pollen transport among bee species. This variation is driven by both morphological and behavioral characteristics and could lead to variation in pollination efficiency (size and diversity of pollen loads deposited on stigmas). Further research is needed to understand how variation in pollen transport will impact plant-pollinator interactions and plant community structure.