Data from: Sperm competition and the evolution of precopulatory weapons: testis size and amplexus position, but not arm strength, affect fertilization success in a chorusing frog

Trade-offs between pre- and postcopulatory traits influence their evolution, and male expenditure on such traits is predicted to depend on the number of competitors, the benefits from investing in weapons, and the risk and intensity of sperm competition. Males of the chorusing frog Crinia georgiana use their arms as weapons in contest competition. Previously, we showed that increased numbers of rivals elevated the risk and intensity of sperm competition due to multimale amplexus, and caused a reversal in the direction of precopulatory selection on arm girth. Here we focused on the factors affecting postcopulatory fertilization success during group spawning, using paternity data from natural choruses. Competitive fertilization success depended on the time spent amplexed and amplexus position. Relative testes size but not arm girth, contributed to fertilization success, but the effect of testes size depended on amplexus position. Our findings offer within species empirical support for recent sperm competition models that incorporate precopulatory male-male competition, and show why an understanding of the evolution of animal weapons requires a consideration of both pre- and postcopulatory episodes of sexual selection.,data for Buzatto et al 2016This data file contains all the information used in our analyses for the manuscript entitled "Sperm competition and the evolution of precopulatory weapons: testis size and amplexus position, but not arm strength, affect fertilization success in a chorusing frog". Each row of this data set refers to a male that participated in a group spawning of the Australian quacking frog 'Crinia georgiana'. Each row has a group spawning ID, the male ID, the female ID, female mass (g), number of males participating in this group spawning, clutch size (number of eggs laid) and spawning time in seconds. The rows also have attributes of these males: number of offspring sired, total body mass (g), soma mass (body mass minus testes mass; g), testes mass (mg), relative testes mass (corrected for body size; mg), snout-vent length (mm), arm girth (mm), relative arm girth (corrected for body size; mm), whether the male amplexed the female in the group spawning, and his main amplexus position (see text). Finally, the proportions of spawning time that each male spent on each possible amplexus position (dorsal, ventral, lateral, amplexing another male, cloaca facing the female's head and not amplexed) are also given.,