Pollinator diversity and short-term foraging specialization

Background/Question/Methods

How will the losses of pollinator species and populations affect plant reproductive function? This is a question of central importance for the long-term persistence of healthy, functioning ecosystems and for the security and productivity of the human agricultural enterprise. We investigated the hypothesis that interspecific competition mediates pollinator short-term foraging specialization on plant species, an important component of successful pollination interactions. If this hypothesis is correct, pollinator species losses will reduce short-term foraging specialization in the remaining pollinators in a community, with potentially deleterious effects on plant reproduction. We tested this hypothesis in three ways: 1) manipulative field experiments that temporarily reduced bee species richness; 2) comparative studies along gradients of bee diversity; and 3) controlled multi-species foraging trials in the laboratory. We conducted comparative and manipulative studies in subalpine meadows in Colorado, and additional comparative work in a largely deforested tropical landscape in southern Costa Rica. We assessed short-term foraging specialization through direct observations of foraging sequences as well as pollen load analysis.

Results/Conclusions

We continue to gather and analyze data, but preliminary results indicate significant reductions in short-term foraging specialization in reduced-diversity manipulated vs. control plots; in less-diverse sites along bee diversity gradients; and in controlled laboratory trials with fewer bee species. These results indicate that, across a wide range of ecological contexts, pollinator community composition may contribute to shaping foraging specialization, which in turn is likely to have important ecosystem functional implications.