Meeting Abstract

P3.158  Monday, Jan. 6 15:30  Perinatal escape performance and morphological scaling of Trinidadian guppies (Poecilia reticulata) DIAL, T.R.*; BRAINERD, E.L.; Brown University terry_dial@brown.edu

One of the most vulnerable, and therefore critical, stages in life is that when a new generation first enters the outside world. Producing relatively mature neonates increases offspring survivorship, but at the reproductive cost of low fecundity. In environments with high predation, high fecundity, and thus small offspring size, is favored. The Trinidadian guppy (Poecilia reticulata) exhibits this paradoxical relationship between size at birth and exposure to predation: populations subject to high predation (HP) produce many, relatively small offspring, whereas populations exposed to few/no predators (low predation; LP) produce fewer, larger offspring. This study investigates escape performance at and around birth in several populations of Trinidadian guppy in an effort to illuminate tradeoffs between selection on life histories and selection on functional morphology. Escape performance was measured within a perinatal window of guppy development from ~1 week prenatal to 1 month postnatal in five different populations of Trinidadian guppy. Preliminary analysis suggests that in one of two major drainages studied, offspring performance at birth increases with size along a gradient of HP environments, but decreases in LP sites, possibly as a result of relaxed selective pressure on escape performance. Fastest escape starts were observed in a population of intermediate offspring size. The other major drainage produced less stark differences in both offspring size and performance. Perinatal performance and morphology will be presented to explore the scaling relationships of form and function through ontogeny between offspring of different populations. These data shed light on the conflicting selective action between life history evolution and morphological adaptation at this most critical neonatal stage.