A phylogenetic comparative method for studying multivariate adaptation

Phylogenetic comparative methods have been limited in the way they model adaptation. Althoughsome progress has been made, there are still no methods that can fully account for coadaptationbetween traits. Based on Ornstein–Uhlenbeck (OU) models of adaptive evolution, we present a method,with R implementation, in which multiple traits evolve both in response to each other and, as inprevious OU models, to fixed or randomly evolving predictor variables. We present the interpretation ofthe model parameters in terms of evolutionary and optimal regressions enabling the study of allometricand adaptive relationships between traits. To illustrate the method we reanalyze a data set of antlerand body-size evolution in deer (Cervidae)