Meeting Abstract

44.4  Saturday, Jan. 5  Life history evolution in Rivulus hartii: interactions between predation, population density, and resource availability WALSH, M.R.**; REZNICK, D.N.; Univ. of California, Riverside; Univ. of California, Riverside matthew.walsh@email.ucr.edu

Predation is often viewed as a dominant mechanism of life history evolution. However, predators often lower population densities and increase resource levels to surviving prey. Such feedbacks between organism and environment may influence the trajectory of evolution, and consequently, the extent to which evolutionary change is driven by predation per se, or factors that covary with predators is unclear. In Trinidad, Hart�s killifish, Rivulus hartii are located in communities that differ in predator intensity. More importantly, population densities decrease (7x) and growth rates increase (2x) with predators. Therefore, evolution in Rivulus may not be a simple response to predation. Here we compared life history traits between sites with predators (�high predation�) and those in which Rivulus is by themselves (�Rivulus only�). We reared 2nd generation born fish under two food levels that approximated natural differences in resources to determine if resource availability and population density influence evolutionary change in this fish. We show that high predation fish matured significantly earlier and at a smaller size. High predation Rivulus also produced many small eggs that take longer to develop and are smaller at hatching. This divergence is consistent with theory that considers predator-induced mortality. However, significant interactions between fish community and food level for age and size at maturity as well as fecundity and eggs size illustrate that both factors influence evolution in Rivulus. For each trait, divergence between communities was reduced under low food conditions. This suggests that Rivulus only fish are adapted to low resource levels or intense density regulation.