Table 2.

Comparison of three evolutionary rate models with Brownian motion. Morphological disparity index (MDI) and maximum-likelihood estimates (lnLH) for the λ-statistic for sperm head length, midpiece length and flagellum length including all families and families with five or more males per species. p-Values were obtained from likelihood ratio tests comparing lambda and early burst (EB) models with Brownian motion.

trait	MDI ± s.d.	Brownian	lambda			EB
		lnLH	λ	lnLH	p	lnLH	p
all families
head	0.56 ± 0.05	42.09	0.43	307.94	<0.001	42.09	n.s.
midpiece	0.48 ± 0.05	−229.69	0.91	−30.92	<0.001	−229.69	n.s.
flagellum	0.30 ± 0.05	−125.96	0.86	92.72	<0.001	−125.96	n.s.
families with five or more males per species
head	0.55 ± 0.08	−23.27	0.25	32.52	<0.001	−23.27	n.s.
midpiece	0.28 ± 0.07	−316.41	0.99	−84.20	<0.001	−140.96	n.s.
flagellum	0.30 ± 0.08	−104.03	0.99	−35.52	<0.001	−90.67	n.s.