Table 2.

Comparisons of mating parameters in invertebrate brooders versus pregnant vertebrates

Mating-system parameter	Invertebrates (mean ± SE)	Vertebrates (mean ± SE)	t-statistic	df	P*	P†
No. of successful mates based on per-brood data	2.19 ± 0.08	1.77 ± 0.02	5.11	651	0.00	0.00
No. of successful mates based on per-species data	3.08 ± 0.64	1.88 ± 0.10	1.85	28	0.07	0.01
Proportion of broods with multiple mates based on per-species data	0.67 ± 0.07	0.51 ± 0.03	2.18	41	0.04	0.02

*Two-tailed t tests assuming unequal variances.

^†Results of a comparison by the Mann-Whitney u test.