Jeremy Rehm, Brigham Young University
Life Science
The recent surge of interest in personality differences between individuals of a single population or members of differing populations has generated numerous new hypotheses that may aid in elucidating patterns of ecology and evolution that were previously considered improbable. Two hypotheses relevant to fish biology relate the size of an organism from a certain predation environment to the level of boldness it exhibits. The first of these (predation hypothesis) predicts small individuals living with predators should not express boldness comparable to their larger counterparts, whereas the other (metabolic hypothesis) predicts the exact opposite. Our study investigated these hypotheses using two sister-taxa fish species in Panama (Brachyrhaphis roseni and B. terrabensis) that exhibit two size classes (large and small) and live in differing predation environments. Additionally, because males are smaller than females in both species, we could look at size-boldness relations within each species. The study, as in others, defined boldness as the amount of time for an individual to emerge from a shelter and into an unfamiliar territory. When the species are analyzed collectively, our results support previous findings that fish from high-predation environments tend to be bolder than those without predators; males tend to be bolder than females; and both mass and standard length positively correlate with boldness. However, within species analyses find that mass and standard length have no significant relation to boldness, and gender was only significant in the predation-exposed B.roseni, where males were bolder. These interesting findings contrast with previous studies, and lead us to question the value of these size-related hypotheses in the process of speciation and, ultimately, evolution.