The presence of a congeneric predicts life history and body shape variation in the livebearing fish, Poeciliopsis baenschi

Authors: Laura E. Scott, Jerald B. Johnson

Year: 2008 (xl)

Abstract

Morphological traits and life history strategies can both be affected by limited resources. Often, environmental factors such as the presence of predators or stream velocity are important determinants of fish body shape and life history. Yet, some of our most compelling examples of ecological factors that shape morphological and life history traits focus on the effects of competition. In this study, we examine variation in life history and morphology among populations of the livebearing fish Poeciliopsis baenschi from central-western Mexico. We take advantage of a natural experiment where P. baenschi co-occur with a close relative, P. turneri, but also exist in isolation in several river drainages. Using geometric morphometrics and quantifying life history traits for P. baenschi we found a significant divergence in sympatric populations compared to their allopatric counterparts for both traits. Sympatric females had wider, more robust bodies and invested less overall to reproduction than allopatric females. We explore the possibility that these differences are driven by competition between these two species. By comparing these traits simultaneously, our work examines the link between body shape evolution and life history divergence among natural populations of fishes.