Trait driven species-specific responses to pollinator losses

Background/Question/Methods

With increasing evidence that global pollinator populations are on the decline it is important to understand the functional impact of pollinator species losses on communities. Going further to understand how traits drive species-specific responses to biodiversity loss will help us interpret complex community and ecosystem functional dynamics.

Our previous research demonstrates that when a single pollinator species is experimentally removed from field plots (in this case removal of the most abundant Bombus species) the remaining pollinators in the community respond to the reduction in interspecific competition with a significant decrease in floral fidelity (the tendency for a pollinator visit the same plant species within a foraging bout), which ultimately leads to a reduction in plant reproductive function. Floral fidelity, and subsequent deposition of conspecific pollen, is an important component of pollination function and is used here as a proxy for ecosystem function.

For this study we tease apart the aggregate community response outline above and explore the how traits influence species-specific response to pollinator losses. We focus on tongue length, a trait known to dictate pollinator resource partitioning. Using the pollinator removals described above we ask 1) Are there species-specific responses to the removal of the dominant Bombus species in a community? 2) Do traits help predict these species-specific responses. We are particularly interested in how traits such as tongue length might influence the response to pollinator losses and we look at the interaction between tongue length of the removed bee species and tongue length of the remaining bee species in the community with respect to floral fidelity. 

Results/Conclusions

We continue to gather and analyze data, but preliminary results indicate there are species-specific responses to pollinator species removals and that tongue length may explain those differences. Removal of a short tongue bee species leads to greater foraging infidelity in remaining bees, especially those that have short tongues. In contrast the removal of long tongued bees does not seem to influence the foraging fidelity of the remaining bee species. Short-tongued bees may have a greater effect on interspecific dynamics because they govern a larger resource base in the community. This work contributes to a richer understanding of how traits drive dynamic interspecific interactions including how traits in conjunction with community composition may shape biodiversity-ecosystem function relationships.