GHALAMBOR, C,K*; WALKER, J.A.; REZNICK, D.N.; Univ. of California, Riverside; Univ. of Southern Maine, Portland; Univ. of California, Riverside: Multi-trait selection, adaptation, and constraints on the evolution of performance: An empirical example using Trinidadian guppies

The conceptual relationship between morphology, performance, and fitness has served as a useful paradigm for understanding the consequences of phenotypic variation in natural populations. However, an understanding of how selection causes adaptive changes in whole organism performance is complicated by the multiple sources and targets of selection and their interactions. We suggest that a thorough understanding of how performance evolves in response to selection will require consideration of: 1) the relative importance of different sources of selection, 2) the diversity of traits that change in response to these selection pressures, 3) the degree to which these traits are integrated and either facilitate or constrain adaptive changes in performance, and 4) the degree to which adaptive changes in one aspect of performance come at a cost to other aspects of performance. Here, we consider these issues using natural populations Trinidadian guppies as a model system. We begin by comparing guppy populations that either coexist with or without piscivorus fishes to test if predators have selected for faster burst swimming speeds. We then investigate how concomitant changes in body shape and life histories interact to collectively influence burst swimming performance. Our results to date demonstrate that predators select for suites of traits to change, which in turn constrain and facilitate adaptive changes in burst swimming performance. We argue that such complex interactions in response to selection are likely to be common because selection ultimately acts on integrated phenotypes rather than individual traits.