Discrete genetic variation in mate choice and a condition-dependent preference function in the side-blotched lizard: implications for the formation and maintenance of coadapted gene complexes

Variation in female preference functions, both genotypic and phenotypic, has been largely ignored in the literature, despite its implications to the maintenance of genetic variation in populations and the resolution of the "Lek paradox." Polymorphic populations, such as in the side-blotched lizard, provide ideal study systems for its investigation, especially in the context of incipient processes of sympatric speciation. Females of the side blotch lizard exist in 2 genetically distinct morphs, yellow throated and orange throated, that experience disruptive selection for life history traits. Males express 3 throat color morphs, blue, orange, and yellow, that exhibit alternative strategies in intrasexual competition. We experimentally tested for female preference in triadic mate choice trials to identify the presence of discrete genetic and condition-dependent variation in female preference function. We found that females did in fact show genetic variation in preference for males but that females also operate a multicondition preference function dependent upon the genotype of the female and her state (number of clutches laid). Females exhibited positive assortative mating prior to the first clutch. However, prior to later clutches, orange females switched choice, preferring yellow males. These findings are discussed in relation to the maintenance of coadapted gene complexes within populations and the prevention of divergent directional selection (population bifurcation) by condition-dependent variation in mate choice. Copyright 2007, Oxford University Press.