Genetic correlations between morphology and antipredator behaviour in natural populations of the garter snake Thamnophis ordinoides

THE genetic coupling of morphology and behaviour means that the evolution of the two types of traits will not be independent: changes in behaviour will result in changes in morphology and vice versa 1,2,3 . This might explain nonadaptive differences in morphology through indirect selection on correlated characters of other categories 4 . Genetic correlations between morphology and behaviour are also the basis for some models of sympatric speciation 5 and of the stability of polymorphisms 6 . Morphology and behaviour are often correlated in nature 7–11 and a genetic basis for such couplings has been demonstrated 12,13 . I present here evidence that colour pattern and antipredator behaviour are genetically coupled in natural populations of the garter snake Thamnophis ordinoides . Similar phenotypic correlations between pattern and behaviour exist among species of North American snakes 14 , indicating that selection for particular combinations of traits may help to maintain genetic covariances and colour polymorphism in Thamnophis ordinoides.