The eastern Pacific coast as a natural transect of the globe for macroecology and biogeography research
Identifying the causes of the biogeographic extent of tropical regions and the shape of global diversity gradients are fundamental, yet unresolved questions in ecology and evolution. While temperature is often a good predictor of biogeographic structure and the shape of diversity gradients, habitat connectivity has received less attention. In this talk, I present new research that shows the biogeographic edges between tropical and extra tropical regions (including a subtropical province) and the richness gradient of rocky shore gastropods along the eastern Pacific coast (>90º of latitude and 23,000 km) are best predicted by habitat connectivity and temperature. Each biogeographic boundary and associated richness gradients coincide with regions of low habitat connectivity, whereas regions of relatively high habitat connectivity are associated with plateaus or humps of diversity. I also present some preliminary data on recent field trips to Baja California to investigate potential geographic range shifts at the northern biogeographic edge of the tropics.