Use of microsatellite paternity analysis to determine male mating success in the western mosquitofish, Gambusia affinis

Abstract

I tested the effects of male body size on male mating behavior and reproductive success in the western mosquitofish, Gambusia affinis. In two separate behavioral experiments (male-male competition and no-competition), I tested the predictions that (1) larger males out-compete smaller males for mates and (2) small males increase their number of mating attempts in the absence of a larger competitor. I estimated male mating success both indirectly (via behavioral experiments) and directly (using microsatellite DNA to assign parentage) and compared the two measures. Results from behavior experiments showed that, when in direct competition, large males were more aggressive and attempted more copulations than small males. In addition, paternity analyses illustrated that large males sired more offspring. I found no significant correlations between male body size (and other correlated traits) and mating success in a male-male competition study, suggesting that relative male size influences male mating behavior but absolute male size does not. When competition was removed, small males mated at equal rates to larger males. Finally, indirect estimates of male reproductive success explained about 67% of the variation in parentage by males, suggesting that indirect measures of mating are good predictors of actual male reproductive success in mosquitofish.

Strong inbreeding depression in male mating behaviour in a poeciliid fish

“…Our study shows that GPA predicts paternity success irrespective of inbreeding. Our results and the results of Deaton (2008) on Gambusia affinis , suggest that GPA can be used as a proxy for paternity success in poeciliid species that use gonopodial thrusts as their most common or only mating tactic.…”

“…Many studies on poeciliid fishes assume that reproductive behaviour correctly predicts mating and paternity success (e.g. Aspbury & Basolo, 2002 in their study on H. formosa ), even though there is only one other very recent study (Deaton, 2008) that has looked at the relationship between the amount of gonopodial thrusts and paternity success. Our study shows that GPA predicts paternity success irrespective of inbreeding.…”

Sex Differences in Mate Preference Between Two Hybridizing Species of Poeciliid Fish

“…All trials were conducted in 76 l aquaria under full-spectrum UV lighting or natural lighting in a greenhouse in Mar.-Oct. of 2006, 2008, and 2009 between 10:00 and 16:00 h. Each trial consisted of four tests in the following order: (1) male visual ⁄ olfactory preference test (n = 40), (2) female visual ⁄ olfactory test (n = 35), (3) single-male open mating test (n = 10), and (4) male-male competition test (n = 23). For each trial, I used four individuals, a male and female of each species.…”

Sexual selection on body size, genitals and heterozygosity:effects of demography and habitat complexity

“…Smaller male G. holbrooki had greater reproductive success. This has long been assumed to be the 375 case in Gambusia spp based on behavioural evidence for insemination success (e.g., Pilastro et al 376 1997), but actual paternity data has been lacking (although Deaton (2008) found a large male 377 advantage based on paternity analysis of 27 trials where a small and a large male competed freely 378 for access to a female within small aquaria). As in many species of poeciliid fishes, male mosquitofish 379 vary substantially in size (range in this experiment 19 -32mm).…”