Table 2.

Standardized linear (β) and quadratic (γ) selection gradients (± SE) derived from regressions between male mating success and body length (TTL) or between male mating success and FTG length (see Figure 2 for abbreviations) in a natural population and in two sets of simulated data.

Natural population	Directional selection gradient		Stabilizing/Disruptive selection gradient
	β	p	γ	p
TTL	0.014 ± 0.042	0.739	0.114 ± 0.072	0.311
FTG	-0.003 ± 0.042	0.934	0.012 ± 0.070	0.937
Simulation 1
FTG	0.182 ± 0.040	< 0.001	-0.074 ± 0.066	0.269
Simulation 2
FTG	0.054 ± 0.042	0.198	-0.178 ± 0.070	0.012

In Simulation 1 female size distribution was shifted towards larger values. In Simulation 2 the variation of male size distribution was increased. P-values in the table were calculated by the least squares analysis. But p-values were also determined by logistic regression and the resulting statistically significant (p < 0.05) selection coefficients are given in bold.