A comparative field study on mating behaviors of the largespring gambusia, Gambusia geiseri

Authors: Richard Lewis, Christopher Kroll, Chad C. Hargrave, Rachel E. Martin, Samir Rosado, Landis Shoemaker, Janalyn West, Raelynn Deaton

Year: 2008 (xl)

Abstract

The largespring gambusia, Gambusia geiseri, is a livebearing mosquitofish that lives in cool water springs throughout central and west Texas. This species was introduced across Texas for mosquito control about 80 years ago. After the introductions, several of the populations survived in clear water springs, and persist today. Because these populations have been isolated for a significant time, they provide an excellent opportunity for in situ studies on potential mechanisms of speciation, including morphological, genetic, behavioral, and/or life history divergence. Deaton et. al. (in prep) have shown that there is significant genetic differentiation across six of these spring populations based on several polymorphic microsatellite loci. These findings suggest that these populations also may show divergence in behavior, population dynamics and/or life history strategies. In this study, we investigated natural mating behaviors across three spring populations in Texas (Comal River, San Marcos River, and Anson Spring) in order to assess potential behavioral differences. We used a repeated measures ANOVA experimental design choosing three target groups of fishes within each habitat, observing them (snorkeling observations) every hour for 20 minutes from dawn until dusk. We asked the following questions: (1) are their significant differences in mating behavior across the populations; (2) what are the natural peak mating times for males; (3) are mating differences correlated with predation, environmental conditions, or variations in sex ratio and/or densities. Data currently are being analyzed across the three populations, and will be presented.