Species and genetic diversity drive resource shifts and ecosystem functioning via behavioral plasticity in bees

Background/Question/Methods

Two key interrelated questions in community ecology are, first, how multiple species coexist on similar resources; and second, the degree to which such resource partitioning drives ecosystem functioning via complementarity.  Most work in this sphere has focused on fixed resource use differentiation between species as a result of natural selection.  Resource shifts driven by phenotypic plasticity, either behavioral or morphological, have received less attention and could lead to different patterns relative to evolutionarily fixed differences.  We studied how plasticity-driven resource use patterns change in response to competition in terms of bee foraging in tightly laboratory experiments with several distinct “species” of artificial flowers.  We assessed the effects of both species richness (one to four bee species) and genetic diversity (Bombus colonies of different genotypes) on bee foraging, in terms of energetic gains, niche breadth, floral fidelity (a critically important component of pollination behavior), and resource complementarity.

Results/Conclusions

We continue to collect data, but preliminary results indicate strong effects of both species richness and genetic diversity on niche breadth and floral fidelity.  With greater species or genetic diversity, niche breadth is reduced, while floral fidelity and complementarity are increased.  These results match well with previous field manipulations we have conducted.  Different bee species respond to competition in qualitatively similar, but quantitatively different ways with respect to niche shifts, fidelity, and complementarity.  Competition did not affect energetic gains in some bee species, but reduced energetic gains in others.  These results indicate that behavioral plasticity may be an important driver of diversity relationships with resource partitioning, species coexistence, and ecosystem functioning.