Table 2. 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.

Taxon	Clades	N	β (p)	SES (ε = 0)	SES (ε = 0.99)
Angiosperms	330	268,301	−0.009 (0.31)	−5.89 (<0.01)	−4.51 (<0.01)
Gymnosperms	12	2,837	0.007 (0.61)	−1.29 (0.10)	−0.38 (0.35)
Ferns	21	9,118	−0.008 (0.41)	−2.44 (0.01)	−1.93 (0.03)
Chondrichthyes	57	991	0.001 (0.82)	−2.77 (<0.01)	−1.83 (0.03)
Actinopterygii	16	18,613	0 (0.99)	−1.01 (0.15)	−0.55 (0.29)
Amphibia	74	6,378	−0.015 (0.10)	−2.88 (<0.01)	−2.34 (0.01)
Mammalia	149	5,279	−0.011 (0.41)	−3.58 (<0.01)	−2.98 (<0.01)
Aves	163	1,0237	0.001 (0.93)	−3.47 (<0.01)	−2.63 (<0.01)
Squamata	53	6,979	0.001 (0.91)	−2.59 (<0.01)	−1.72 (0.04)
Araneae	24	8,776	−0.008 (0.40)	−2.58 (<0.01)	−2.03 (0.02)
Coleoptera	183	342,201	0.017 (<0.01)	−4.27 (<0.01)	−1.92 (0.03)
Diptera	51	87,899	−0.008 (0.40)	−3.35 (<0.01)	−2.65 (<0.01)

“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.