Genetic correlations between traits can be from two different perspectives in evolutionary theory. On the one hand, genetic correlations may be seen as a constraint because they can channel a population’s evolutionary trajectory in a direction that may be less than optimal. On the other hand, genetic correlations may themselves evolve when selection favors certain groups of traits and thus may be seen as signatures of adaptation.
We know little about how patterns of genetic correlations (the “G matrix”) evolves in nature. Caribbean Anolis lizards provide a unique opportunity to study the evolution of G because morphologically similar habitat specialists (or “ecomorphs”) have evolved multiple times in different lineages, allowing us to separate the effects of shared history from shared ecology. In collaboration with Butch Brodie and Jonathan Losos, we have measured the G matrix in seven Anolis species that represent unique origins of three ecomorphs from three different lineages.
We are also using this system to ask quantitative genetic questions about development and sexual dimorphism. In collaboration with Bob Cox, we are examining evolutionary patterns of between-sex genetic correlations within a single species, the brown anole (Anolis sagrei). This lizard is highly sexually dimorphic, but the degree of dimorphism varies highly across populations, allowing us to explore evolutionary changes in the genetic variation underlying sex differences.
Cox, R. M., Cox, C. L., McGlothlin, J. W., Card, D. C., Andrew, A. L., and Castoe, T.C. In review. Genetic (dis)integration: ontogenetic increases in sex-biased gene expression accompany the developmental breakdown of between-sex genetic correlations.
McGlothlin, J. W. 2010. Combining selective episodes to estimate lifetime nonlinear selection. Evolution 64: 1377-1384 (with Correction).
Galloway, L. F., J. R. Etterson, and J. W. McGlothlin. 2009. The contribution of direct and maternal genetic effects to life-history evolution. New Phytologist 183: 826-838.
Brodie, E. D., III, and J. W. McGlothlin. 2007. A cautionary tale of two matrices: the duality of multivariate abstraction. Journal of Evolutionary Biology 20: 9-14.
McGlothlin, J. W., P. G. Parker, V. Nolan Jr., and E. D. Ketterson. 2005. Correlational selection leads to genetic integration of body size and an attractive plumage trait in dark-eyed juncos. Evolution 59: 658-671.