Intraspecific variation in life history traits of the panamanian electric fish Brachyhypopomus Occidentalis

Abstract

The purpose of this thesis was to investigate intraspecific variation of life history traits in the electric knifefish Brachyhypopomus occidentalis under natural conditions, and to explore how individuals optimize their reproduction and brain size under varying predation risks. In the first chapter, I describe the reproductive biology of B. occidentalis, using several reproductive traits selected in both females and males to provide insight on the reproductive effort of mature knifefish. I provide field evidence supporting the hypothesis that predation risk environment and geographical isolation drive variation in female reproductive strategies. In the second chapter, I explore whether predation risk and drainage contributed to brain mass variation B. occidentalis. I also explore how ontogenetic scaling relationships influence brain mass, and how this association may have been affected by predation. I show that predation risk is an important driver of brain mass variation and discuss the potential implications for the fish and other highly encephalized vertebrates.