Clinal Variation in Cold Adaptation in Mus domesticus: Verification of Predictions from Laboratory Populations

Abstract

The aim of this study was to test whether heritabilities of traits contributing to cold adaptation and genetic correlations among those traits, all obtained from laboratory populations, could predict adaptive evolution in natural populations. Body weight and nesting scores had substantial heritabilities and were expected to respond to selection, whereas body temperature and weight of brown adipose tissue had negligible heritabilities and should not be easily modified. In laboratory-reared mice originating from five geographical populations forming a cline along the east coast of the United States, body weight and nesting did exhibit adaptive variation: more northern mice were heavier and built larger nests. These traits may have been shaped by selection acting through ambient temperature differences. Body temperature and brown adipose tissue did not vary clinally, although there were some differences among the populations. Reaction norms for nesting at warm and cold temperatures were similar for laboratory and natural populations; genotypic rank order rarely changed across temperatures. The similar responses to natural and artificial selection were expected from the high genetic correlation between nesting scores at the two temperatures seen in laboratory populations. The heritability of plasticity predicted the observation that mice most strongly selected for nesting would show the greatest response to cold.