Jeffrey Walker Ph.D.

My lab focuses on the theoretical and empirical investigation of functional constraints on phenotypic evolution at both microevolutionary (rate and direction of phenotypic change) and macroevolutionary (patterns of covariation among populations and species, convergence) levels. “Functional constraints” has been variously, and often vaguely, defined. Consequently, we are working on a simple, but comprehensive, quantitative genetic model of phenotypic evolution that unambiguously defines old terms such as functional constraints, functional integration, and functional trade-offs and suggests new terms such as functional facilitations and functional evolvability. The model makes predictions about patterns of trait variation and intertrait covariation within and among populations. Tests of the model require measures of the ability of organisms to perform fitness-related tasks such as acquire prey, avoid predators, and attract mates. The empirical work in the lab, then, tends to resemble an animal Olympiad. The model also requires functionally relevant measures of morphology, which we satisfy with a combination of geometric morphometric variables and biomechanical shape indices. We use Trinidadian guppies, threespine sticklebacks, minute flying wasps (Mymaridae and Trichogrammatidae) and, of course, the fruit fly, Drosophila melanogaster, to test various aspects of the functional constraints model.

Hendry, A.P., Hudson, K., Walker, J.A., Räsänen, K., and Chapman, L.J. 2011. Genetic divergence in morphology-performance mapping between Misty Lake and inlet stickleback. Journal of Evolutionary Biology, 24: 23–35.

Walker, J. A. 2010. An integrative model of evolutionary covariance: A symposium on body shape in fishes. Integrative and Comparative Biology, 50: 1051-1056.

Walker, J.A. 2007. A general model of functional constraints on phenotypic evolution. American Naturalist, 170: 681-689.