Low interspecific variation and no phylogenetic signal in additive genetic variance in wild bird and mammal populations

Abstract

Evolutionary adaptation through genetic change requires genetic variation and is a key mechanism enabling species to persist in changing environments. Although a substantial body of work has focused on understanding how and why additive genetic variance (VA) differs among traits within species, we still know little about how they vary among species. Here we make a first attempt at testing for interspecific variation in two complementary measures of VA and the role of phylogeny in shaping this variation. To this end, we performed a phylogenetic comparative analysis using 1822 narrow-sense heritability (h2) for 68 species of birds and mammals and 378 coefficients of additive genetic variance (CVA) estimates for 23 species. Controlling for within-species variation attributable to estimation method and trait type, we found some interspecific variation in h2 (~15%) but not CVA. Although suggestive of interspecific variation in the importance of non-(additive) genetic sources of variance, sample sizes were insufficient to test this hypothesis directly. Additionally, although power was low, no phylogenetic signal was detected for either measure. Hence, while this suggests interspecific variation in VA is probably small, our understanding of interspecific variation in the adaptive potential of wild vertebrate populations is currently hampered by data limitations, a scarcity of CVA estimates and a measure of their uncertainty in particular.