Effect of trait dimensionality on the coevolution of mating traits under antagonistic selection

     Sexual conflict has been postulated to result from asymmetries in mating costs experienced by males and females. Whenever mating is costly (i.e., it has direct effects on individual fitness), mating resistance and preference traits are expected to evolve, often in females, prompting the evolution of persistence traits in the opposite sex, hence triggering a runaway co-evolutionary chase limited only by the costs of producing these traits. In co-evolutionary trends like this, it is common to find situations in which one of the sexes has co-opted some phenotypic feature as a novel mating trait, often as a way to exploit pre-existing sensory biases in the opposite sex. This morphological dynamism implies that the composition and dimensionality of the phenotypic complex termed "mating traits" is constantly changing in evolution, so that each such innovation brings about a new set of challenges for the opposite sex in terms of coordinating an appropriate evolutionary response when the variance to do so may require a congruent response among uncorrelated traits. To being exploring the dynamics of this co-evolutionary race, I have begun to model the effects of dimensionality of persistence and resistance traits using quantitative genetic models of sexual conflict. In these models, pleiotropic effects within mating-trait complexes are used to represent a range of covariation structures with different dimensionalities, including integrated and modular traits. From these models it is then possible to examine how differences of dimensionality within sexes affect the magnitude and direction of mean phenotypic change of each trait and sex.

Phase-plane representation of the dynamics of a female (x) and male (y) trait belonging to a complex of independent (left) and integrated (right) mating traits under antagonistic selection over mating rate. Color contours represent the joint fitness surface of these traits.