Species Richness and Cladal Diversity

This chapter describes relationships between species richness and cladal diversity in the two largest regional ichthyofaunas of the Americas: the Amazon and Mississippi superbasins. It explains that species richness profiles of both faunas are hollow curve distributions in which most species are members of a few highly diverse clades and in which most clades are species poor. The species-richness profiles also show that the majority of clades in both faunas were derived from marine lineages during the Cenozoic, although these clades represent only a small fraction of the species.