A key paradigm in ecology and evolution is that functional traits determine resource use, thereby setting limits on distribution and abundance. This relationship between phenotype, performance, and ecology is powerful: if we can mechanistically link functional traits to the outcome of species interactions, we can generate testable predictions about species coexistence in different environments. Many examples link functional traits to individual fitness; however, we have surprisingly little evidence that trait differences can predict resource use in natural settings, or that coexistence in the field can be mechanistically derived from specific individual traits. The Anolis lizards of the Greater Antilles are a textbook example of resource partitioning. Many decades of research has identified functional traits related to key resource axes—structural habitat, thermal microhabitat, and diet—that structure anole communities. Day geckoes (Phelsuma)are ecologically similar to anoles, and recent introductions to the Hawaiian Islands have created a novel assemblage of Phelsuma and Anolis. To test whether Anolis traits predict resource use and overlap with day geckoes, we measured functional traits relevant to all three resource axes and measured resource use and fitness correlates in experimental enclosures with standardized resource availability where we also manipulated the lizard species assemblage.
Results/Conclusions
The three species (A. carolinensis, A. sagrei, P. laticauda) all overlap in traits related to diet and thermal microhabitat, supporting the potential for competiton. For structural habitat, there is a trade-off in clinging ability on rough vs. smooth surfaces. Taken together, the trait data suggest that A. carolinensis may be particularly disadvantaged because it is the only species that overlaps with both of the others on all three axes. Clinging ability predicts habitat use in enclosures, with each species using more the substrates on which it performs best. Behavioral observations indicate a limited role for direct interference. We have documented habitat shifts in the presence vs. absence of putative competitors, and ongoing analyses aim to determine whether these shifts in perch use are associated with changes in thermoregulation and/or diet. To date, we have documented the same interaction between the anoles that has occurred in the southeastern US, and that functional traits for Anolis generalize to Phelsuma. Our goal is to further generalize these results to predict what will happen longterm in this actively assembling community.