Testing the Novelty Hypothesis as an explanation of heterospecific mating in livebearing fishes

• In Event: Systematics and Evolutionary Biology Oral Session & Section Meeting

Abstract

In nature, males should prefer to mate with females of the same species to avoid hybridization. However, recent studies have shown levels of male permissiveness being higher than expected. The Novelty Hypothesis is a possible explanation for such increases. This hypothesis states that males are more likely to notice, and subsequently mate with, a female they perceive as different, resulting in “mating mistakes.” We tested this hypothesis in two species of mosquitofish from Central Texas: Western mosquitofish (Gambusia affinis) and Largespring gambusia (Gambusia geiseri). In order to examine whether the novelty of a female can provide a mechanism for permissiveness, males of both species were acclimated for approximately three to six weeks within three groups: (1) conspecific, (2) heterospecific or (3) both conspecific and heterospecific females. Males were placed in a 10-gallon tank to examine both association time and copulation attempts towards conspecific and heterospecific stimulus females. Based on mean association time differences between the six treatments, males acclimated with conspecific females desired heterospecific females more frequently at similar rates across species. After measuring mean differences in gonopodial displays towards females, males displayed significantly more towards heterospecific females after being acclimated with their own species, rather than both or the novel species. These factors indicate that mating permissiveness was evident across both species, however, they also show that mating permissiveness was significantly higher in males not exposed to the other species.

Authors

• Dylan J Wichman, St. Edward's University

• Raelynn Deaton Haynes, St. Edward's University