Abstract
Just as mating patterns can promote speciation or hybridization, the presence of hybridization can shape mating patterns within a population. In this study, we characterized patterns of multiple mating and reproductive skew in a naturally hybridizing swordtail fish species, Xiphophorus birchmanni. We quantified multiple mating using microsatellite markers to genotype embryos from 43 females collected from 2 wild populations. We also used a suite of single-nucleotide polymorphism markers to categorize females and their inferred mates as either parental X. birchmanni or as introgressed individuals, which carried alleles from a sister species, X. malinche. We found that parental and introgressed X. birchmanni females mated multiply with both parental and introgressed males. We found no difference in mating patterns or reproductive skew between parental and introgressed X. birchmanni females. However, nonintrogressed X. birchmanni males mated more often with large, fecund females. These females also had the greatest levels of skew in fertilization success of males. Thus, our results show that X. birchmanni has a polygynandrous mating system and that introgression of X. malinche alleles has only subtle effects on mating patterns in this species.
Highlights
Individual reproductive success is shaped by a number of factors, including ecological, social, and individual effects (Jones and Ratterman 2009; Alonzo 2010; Kuijper et al 2012)
Previous research has demonstrated that female choice for novel male phenotypes is likely to occur in X. birchmanni populations (Rosenthal 2013), which could explain the observed introgression of X. malinche alleles into these X. birchmanni populations
The 4 microsatellite markers optimized for this study from X. maculatus were highly variable with 11–27 alleles per locus identified in the pool of gravid females (Table 1)
Summary
Individual reproductive success is shaped by a number of factors, including ecological, social, and individual effects (Jones and Ratterman 2009; Alonzo 2010; Kuijper et al 2012). Just as the introduction of heterospecific alleles may change the distribution of traits and preferences related to precopulatory mate choice, hybridization may impact phenotypic diversity in traits linked to sperm competitive ability (Joly et al 1997) and alter reproductive success via postcopulatory processes. These factors may affect within-brood reproductive skew, which is the bias of a female’s reproductive effort towards 1 or a few of her mates, due to unequal sperm. Previous research has demonstrated that female choice for novel male phenotypes is likely to occur in X. birchmanni populations (Rosenthal 2013), which could explain the observed introgression of X. malinche alleles into these X. birchmanni populations
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