Abstract
Identifying targets of selection is key to understanding the evolution of sexually selected behavioral and morphological traits. Many animals have coercive mating, yet little is known about whether and how mate choice operates when these are the dominant mating tactic. Here, we use multivariate selection analysis to examine the direction and shape of selection on male insemination success in the mosquitofish (Gambusia holbrooki). We found direct selection on only one of five measured traits, but correlational selection involving all five traits. Larger males with longer gonopodia and with intermediate sperm counts were more likely to inseminate females than smaller males with shorter gonopodia and extreme sperm counts. Our results highlight the need to investigate sexual selection using a multivariate framework even in species that lack complex sexual signals. Further, female choice appears to be important in driving the evolution of male sexual traits in this species where sexual coercion is the dominant mating tactic.
Highlights
Studies of sexual selection generally focus on species in which males court females and have extravagant ornaments and/or complex courtship displays
Phenotypic correlations between male traits indicate that larger males had longer gonopodia, and that males that spent more time following females made more mating a 2015 The Authors
This is unsurprising given that insemination success is determined by multiple mechanisms of sexual selection
Summary
Studies of sexual selection generally focus on species in which males court females and have extravagant ornaments and/or complex courtship displays. Many researchers have adopted a multivariate approach to look at the resultant selection on male traits due to female mate choice (Lande and Arnold 1983; Blows and Brooks 2003). Well-known examples include premating struggles in waterstriders (Arnqvist 1992) and the many Poeciliid fishes where males incessantly harass females (Plath et al 2007). These species rarely exhibit courtship displays or bear ornamental traits. Female mating resistance has the potential to generate variation in male mating success (Westneat et al 1990; Wiley and Poston 1996; Jormalainen 1998; Gavrilets and Arnqvist 2001) due to sexual selection on traits that increase males’ insemination success
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