Age-richness relationships within 12 higher taxonomic groups with dense subclade sampling, compared to expected relationships under a relaxed-rate model of among-clade variation in net diversification rates.

“Clades” gives the number of subclades within each taxon, and N is the total species richness based on our compilation (Table S2). β gives observed PGLS slope for the relationship between log(richness) and clade age (in millions of years) for each group. Two-tailed p values for test of null hypothesis (β = 0) are given in parentheses after slope. SES gives the standardized effect sizes of the observed slope relative to model-predicted values under two relative extinction rates (ε); the corresponding cumulative tail probability is given in parentheses.