Multispecies Character Displacement in Mexican Freshwater Fish Communities

Authors: Andrea Roth-Monzón, Jerald B. Johnson

Year: 2018

Abstract

Competition has long been recognized as a central force in shaping evolution, particularly through the mechanism of character displacement. However, research on character displacement is biased as it has focused almost exclusively on pairs of interacting species while ignoring multispecies interactions. Yet communities are seldom so simple that only pairs of species interact, and it is not clear if inferences from pairwise interactions are sufficient to explain patterns in nature. A more realistic approach is to ask how traits evolve when multiple species interact. Here we test for character displacement in a natural system of freshwater fishes in western Mexico that contains different combinations of up to four closely related species of the genus Poeciliopsis. We focus on three fundamental questions in this system: (1) is there character displacement in the different species of Poeciliopsis, (2) how does number of co-occurring species affects character displacement in each species, and finally, (3) does number of co-occurring species affects trait displacement equally for all species. This work is important because it recognizes that trait evolution can differ as a function of number of species interacting, but could also be different for each of the interacting species. Our work suggests that future studies of character displacement should move beyond pairwise competitive interactions to provide a more realistic understanding of how species evolve in natural fish communities in the wild.