Table 1. Relations between sperm length, sperm straight-line velocity and mass-specific metabolic rate in eutherian mammals.

Dependent variable	Independent variable	Slope	R 2	p-value	t-value	λ value	Effect size	CL(-)	CL(+)	n
Sperm straight-line velocity	Mass-specific metabolic rate	0.0592	0.38	0.0001	4.4282	<0.001ns,*	0.6164	0.3672	1.0712	34
Total sperm length	Mass-specific metabolic rate	0.2399	0.40	<0.0001	4.6637	<0.001ns,*	0.6304	0.3900	1.0941	34
Sperm straight-line velocity	Total sperm length	0.4783	0.49	0.0144	2.5924	<0.001ns,*	0.4221	0.0982	0.8023	34
	Mass-specific metabolic rate	0.1473		0.0442	2.098		0.3526	0.0164	0.7204

Phylogenetically controlled multiple regression analyses (PGLS). Superscripts following the λ value indicate significance levels (n.s. p>0.05; *p<0.05) in likelihood ratio tests against models with λ = 0 (first position) and λ = 1 (second position). Effect size r calculated from the t values and the non-central 95% confidence limits (CLs) for the z-transformed value of r are presented. Confidence intervals excluding 0 indicate statistically significant relationships. P-values and CL that indicate statistical significance are shown in bold. All variables were log₁₀-transformed. n: number of species.