Genetic correlation complicates the interpretation of phylogenetic transitions in sexually selected traits

HL11 (1994) proposed that under special circumstances the models of nonadaptive (arbitrary) mate choice can be rejected on phylogenetic grounds. Specifically, in the absence of changes in female preferences or viability costs. Hill argued, the sensory exploitation (Basolo, 1990; Ryan et al., 1990) and runaway (Fisher, 1958; Lande, 1981) models provide no mechanism for reduction of a sexually selected trait. Although the sensory exploitation model clearly generates unique historical predictions (Basolo, 1990; Meyer et al., 1994; Ryan et al., 1990), the runaway model was previously thought phylogeneticaDy indistinguishable from models of adaptive mate choice (Kirkpatrick and Ryan, 1991). Hill's method, if valid, would be a major breakthrough in die study of sexual selection. Unfortunately, I think Hill overlooked a factor diat invalidates his method for die example he provided and in general. To illustrate my argument with a concrete example, I first summarize key results from Hill's exemplary study of house finches (Carpodacus medcanus).