Effects of a trematode infestation on body condition, reproduction and mating behaviors in a livebearing fish

Abstract

AbstractMost studies of parasite-mediated sexual selection target organisms where female or male mate choice is the major driving force of sexual selection, leaving the effects of parasites on coercive mating systems understudied. Here, we investigated the role of a trematode infestation (black spot disease (BSD)) on female body condition, female fecundity, male coercion, and female resistance in a coercive livebearing fish (the western mosquitofish, Gambusia affinis). We tested the following predictions: (1) infected females are in poorer body condition and have lower fecundity than uninfected females; (2) males prefer to coerce uninfected females; (3) infected males coerce less frequently than uninfected males; and (4) infected females are less resistant to male coercion. In contrast to our first prediction, infected females had more energy reserves than uninfected females during one month and infected females had increased fecundity compared to uninfected females. In the behavior experiments, we found BSD influenced male coercion in two of our experiments supporting our third, but not second or fourth, prediction. These results suggest this parasitic infestation may play a minor role in sexual selection on G. affinis.