Species richness varies dramatically among clades across the Tree of Life, by over a million-fold in some cases (e.g. placozoans versus arthropods). Two major explanations for differences in richness among clades are the clade-age hypothesis (i.e. speci...
Scholl, J. P. (Creator), Wiens, J. J. (Creator) (2016). Supplementary material from "Diversification rates and species richness across the Tree of Life". figshare. 10.6084/m9.figshare.c.3457455.v1