Conclusion
Taken together, our results emphasize the role of macroevolutionary diversity in determining community structure. Over ecological time, communities at different compositional start points will converge to similar functional members, even if species identity varies (Fukamiet al. 2005). We suggest a similar process of community filling over evolutionary time—so long as evolutionary opportunity is available, speciation can fill local communities, allowing them to follow similar ecological trajectories. Evolutionary opportunity allows for regional environmental specialists to form, increasing beta-diversity and supplementing alpha-diversity at biological suture zones. Where speciation is comparatively limited, widespread species fill rare environments as best they are able, but sub-regional faunas are unable to form, and local diversity in the rare environments and their suture zones remains impoverished. Accounting for such dynamics may help reconcile contradictory results in elevation diversity profiles across systems, and shed new light on how local or regional factors control community structure and diversity.