Table 2.

Results of regression analyses relating diet variation to population TNW

Taxon	Empirical results					Null model results		Test whether empirical ≠ null
	Slope	SE	t	P	r2	Slope	SE	F	df	P
Three-spine stickleback	0.401	0.043	9.32	<0.001	0.906	0.229	0.037	9.25	1,18	0.007
Eurasian perch	0.424	0.034	12.55	<0.001	0.908	0.212	0.070	7.42	1,32	0.010
Whelk	0.331	0.042	7.84	0.004	0.953	0.209	0.017	7.13	1,6	0.037
Brazilian savannah frogs	0.217	0.027	8.05	<0.001	0.915	0.076	0.035	10.22	1,12	0.008
Anolis lizards	0.003	0.001	3.56	0.038	0.809	n/a*	n/a	n/a	n/a	n/a

The slope (with SE) is given for both the actual regression relationship and the null relationship based on sampling effects. The t, P, and r² values are for the empirical regression alone; the F and P values are given for the TNW source interaction term in a general linear model comparing the slopes of the empirical and null relationships (″source″). A significant interaction term indicates that the empirical and null slopes differ.

*n/a, not applicable. Note that the Anolis lizard relationship uses a different metric for diet variation, so it is not comparable with the other cases. In addition, raw data are not available for the Anolis comparison, so resampling was not possible.