Biogeography and Comparative Phylogeography of New-World Crocodylians

Biogeography is an area of study dedicated to understanding the evolutionary processes that resulted in current organismal distribution patterns. In general, exclusively terrestrial and exclusively aquatic vertebrates have well-studied and defined biogeographic patterns in the New World, but the biogeography of semiaquatic organisms is still poorly understood. In this chapter we discuss the biogeographic patterns and processes of New-World crocodylians. Although dispersal was probably an important process for the diversification of the ancestors of this group, the species/lineages—especially those of the South Americans—have their geographic distributions delimited by natural geographical barriers such as watershed divides, waterfalls and rapids, and captured watersheds, but also ecological specialization and competitive exclusions. The species/lineages occupying these areas show nearly identical divergence times, pointing to common historical processes that drove the evolution and divergence of these species/lineages. Recent studies have shown that widely distributed species have diversified into a significant number of independent evolutionary lineages. Knowing the biogeographic patterns of this group is of fundamental importance for conservation, since in the Anthropocene the effects of changes caused by man are devastating, destroying in a short period of time what nature took thousands/millions of years to build.