Table 2.

Minimal adequate linear mixed-effects model explaining the variation in the proportion of second-male sperm (S₂) among all sperm retained by the female, after sequential elimination of nonsignificant random and fixed effects (Materials and Methods)

Fixed terms	Estimate ± SE	ddf	t	P
Time to ejection	0.17 ± 0.02	808.2	5.65	<0.0001
Resident sperm (first male)	−0.62 ± 0.03	803.1	−19.14	<0.0001
Sperm transferred (second male)	0.55 ± 0.03	849.4	16.81	<0.0001

Following sequential elimination, the maternal isoline (LLR = 8.11, P = 0.004) and paternal isoline (LLR = 2.73, P = 0.099) were the only random effects remaining in the minimal adequate model. Conditional model R² = 0.38; n = 855 females from 90 diallel crosses derived from 10 isolines. For full model see Table S5. Parameter estimates are standardized. Ddf, denominator degrees of freedom estimated using Satterthwaite’s approximation.