Insights of functional performance into morphological modularity: how does selection for performance contribute to trait interactions?

Abstract

One of the greatest challenges of evolutionary biology is to understand the evolution of complex phenotypes composed of several traits that interact with each other. The theory of phenotypic modularity represents interactions among traits as genetic and phenotypic covariation or correlation. A fundamental undertaking in modularity studies is to uncover which evolutionary forces shaped a certain pattern of trait correlation in natural populations. Riedl's hypothesis states that genetic and developmental modularity evolved to match functional interactions among traits by the action of stabilizing selection. In this proposal, we aim to test Riedl's hypothesis by comparing the pattern of phenotypic covariances among traits with the pattern of stabilizing and correlational selection related to specific functional performances in lizards. We will work with four species of Brazilian tropidurinae lizards that have morphological and ecological divergence. Most specimens have already been CT-scanned to assess their skull or limb bones. We will place 3D landmarks on the bones to extract linear measurements with which we will construct phenotypic covariance matrices (P-matrices) for all species. Then, we will estimate the non-linear regression coefficients of the measurements on bite force and locomotor performance, to construct the functional gamma-matrix (stabilizing and correlational selection). We expect the covariation pattern of the skull and limb traits to be similar to the pattern of selection embedded in the gamma-matrix for bite force and locomotor performance, respectively. (AU)