Meeting Abstract
How a trait responds to selection depends not only on its variance, but on its covariance with other traits also under selection. Understanding the genetic basis of trait covariation can provide key insights into how suites of correlated traits diverge across populations. We used Trinidadian guppies (Poecilia reticulata) to explore covariation in divergent traits. Morphology, life history, and antipredator behaviors have undergone parallel evolution in multiple river systems as high-predation ancestors colonized sites with low predation intensity. We generated genetically diverse families by creating hybrid-inbred lines. We first crossed high- and low-predation populations from the same drainage with the potential to interbreed in nature, and then bred the resulting hybrid siblings together for two generations. We measured size, color pattern, brood size, and antipredator behaviors over 3 generations. As expected, F2 hybrids showed intermediate antipredator behavior between parental populations. Cross direction yielded striking asymmetries in the behavior of F2 fish, such that antipredator behaviors were more similar to the cross’s maternal ancestral population. Covariation among behaviors was also influenced by cross direction: crosses between the maternal high-predation and paternal low-predation population had weakened correlations between behaviors compared to the other cross types. Further, many traits in this cross direction showed values outside the range of the parent populations (heterosis). Our results suggest that parent-of-origin effects play a large role in the expression of suites of divergent traits in Trinidadian guppies. This flexibility in trait covariances suggests that complex genetic influences on phenotypic covariances may shape parallel evolution of life history, behavior, and morphology.
