67.2 Saturday, Jan. 5 Comparing disparity between traits using the Ornstein-Uhlenbeck model: a test of functional constraint on the eyes of labrids PRICE, S. A.*; SCHMITZ, L.; ANDERSON, P.S.L.; BOETTIGER, C. L.; WAINWRIGHT, P. C.; University of California, Davis; Keck Science Department, Claremont McKenna, Pitzer and Scripps College,; University of Massachusetts, Amherst,; University of California, Davis; University of California, Davis firstname.lastname@example.org
On a macroevolutionary scale the comparison of rates of phenotypic evolution between traits within a clade is useful for answering questions about niche conservatism, natural versus sexual selection as well as functional constraints. However, such comparisons present several challenges including the use of comparable standardized units and incorporating differences in phylogenetic signal. Using simulations we illustrate how disparity measured using the Brownian motion rate parameter estimated on an untransformed phylogeny can be confounded by phylogenetic signal. Rates are inflated when phylogenetic signal is weak, as the phylogeny overestimates the covariance among species. As a possible solution we show that calculating disparity using the variance estimated from the Ornstein-Uhlenbeck model can account for differences in phylogenetic signal. With this method we test the hypothesis that the eyes of labrids, a diverse group of reef fish, exhibit less disparity than the fins, teeth and jaws and find that the disparity within the two eye traits is substantially lower. We suggest that this result is due to functional constraints as most potential morphological changes to a fishes eye will ultimately lead to the projection of an under-focused image onto the retina causing loss of function.