Table 2.

Selection gradients (±s.e.) computed from survival of female progeny during maturation as a function of clutch-size variation of mothers (figure 2). (Selection gradients were also computed for three manipulations of ovarian development: follicle ablation reduced clutch size; FSH implants increased clutch size; and corticosterone implants increased clutch mass. Significance of selection surfaces is given by: ^*p=0.05; ^**p<0.05; ^***p<0.01. Significant directional selection gradients (β) that acted on genetic variation were detected in all 3 years, and a disruptive selection gradient (γ) was observed in 1992. Genetic selection gradients are comparable in magnitude and direction to experimentally induced selection gradients in all but one case (e.g. no quadratic selection was detected in 1992 using corticosterone implants, see figure 2).)

		selection differential form experimental manipulations (β)
	selection on genetic variation (β and γ)	corticosterone	follicle ablation	FSH
1991	β=0.304±0.145**	0.403±0.196**
1992	β=−0.622±0.310**	−0.045±0.040n.s.	−0.101±0.044**
	γ=0.067±0.032**
1993	β=−0.170±0.084**	−0.136±0.070*	−0.313±0.105***	−0.258±0.093***