Combining phylogeny, traits and distribution to understand mechanisms shaping hummingbird diversity

Background/Question/Methods

Determining the role of environmental filters, dispersal limitation and biotic interactions influencing community composition is an on-going question in ecology.  Species distribution models, which capture some environmental filters, often suggest that species could occur in regions where they are currently absent. This is potentially caused by dispersal limitation or biotic interactions.  One way to evaluate why species do not occur in all the places they are predicted is to compare the predicted assemblages (all species predicted to occur in a given region) versus the realized assemblages (all species that do occur in a given region).  If a species is predicted to occur in a given assemblage, but is absent, we ask whether a closely related or functionally similar species is present. We use the hummingbirds that occur in the Andean region of South America to evaluate the potential role of dispersal limitation and biotic interaction in shaping assemblages.

Results/Conclusions

Our environmentally-weighted distance (i.e., a measure of dispersal potential), provides the strongest explanation of which species could occur in a given assemblage but are absent.  However, presence of a closely related species in a given assemblage also influences the probability that a given species will be in a given assemblage.  Taken together, these results provide evidence that biotic interactions may influence assemblage structure at broad spatial scales.