Abstract
BackgroundA large number of studies in postcopulatory sexual selection use paternity success as a proxy for fertilization success. However, selective mortality during embryonic development can lead to skews in paternity in situations of polyandry and sperm competition. Thus, when assessment of paternity fails to incorporate mortality skews during early ontogeny, this may interfere with correct interpretation of results and subsequent evolutionary inference. In a previous series of in vitro sperm competition experiments with amphibians (Litoria peronii), we showed skewed paternity patterns towards males more genetically similar to the female.Methodology/Principal FindingsHere we use in vitro fertilizations and sperm competition trials to test if this pattern of paternity of fully developed tadpoles reflects patterns of paternity at fertilization and if paternity skews changes during embryonic development. We show that there is no selective mortality through ontogeny and that patterns of paternity of hatched tadpoles reflects success of competing males in sperm competition at fertilization.Conclusions/SignificanceWhile this study shows that previous inferences of fertilization success from paternity data are valid for this species, rigorous testing of these assumptions is required to ensure that differential embryonic mortality does not confound estimations of true fertilization success.
Highlights
Patterns of paternity in offspring are routinely used to infer fertilization success for analysis of mating system evolution, genetic compatibility of mates, or innate competitive ability in sperm competition [e.g. 1,2,3]
We show elsewhere that the probability of paternity in the Peron’s tree frog (Litoria peronii) under conditions of sperm competition is influenced by the relatedness of the two competing males in relation to that of the female [2], and recent data demonstrate that among-male differences in siring success has an innate component so that male-male differences in siring success are consistent across females [10]
Hatching success varied between trials from 46–100% with an average of 82%63% (s.e.m) of eggs hatching across all 16 sperm competition trials
Summary
Patterns of paternity in offspring are routinely used to infer fertilization success for analysis of mating system evolution, genetic compatibility of mates, or innate competitive ability in sperm competition [e.g. 1,2,3]. Fertilizing species are increasing being used in studies of sexual selection as they offer excellent systems for separating out genetic and nongenetic effects on fertilization success and offspring fitness as their external mode of fertilization makes them amenable to controlled laboratory studies using in vitro fertilization [e.g., 2,6,7,8,9,10]. These systems allow for the direct assessment of fertilization success and mortality can be followed through various stages of ontogeny, something that is much less tractable in internally fertilizing species. In a previous series of in vitro sperm competition experiments with amphibians (Litoria peronii), we showed skewed paternity patterns towards males more genetically similar to the female
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