Sex differences in the evolution of live-bearing fish

Samples of fish species from the Poeciliidae family show the diversity in color, fin size and body shape. Kansas State University researchers studied 112 species of these live-bearing fishes and found that males and females evolve differently. Image courtesy of Kansas State University

Dr. Michael Tobler and Dr. Zach Culumber at Kansas State University examined 112 species of live-bearing fish (Poeciliidae) and have made some interesting discoveries about their evolution. Their analyses included information on body shape, fin size, where the species are found and information on global climate. What they discovered is that the evolution of female fish is influenced by natural selection as well as the environment, whereas sexual selection plays a larger role in the evolution of males. In addition, the body shape of male fish was also found to be evolving faster than in females. According to Dr. Tobler, "The assumption that people often make is that on a broad evolutionary scale, natural selection and adaptation drive most of the patterns in the evolution of traits. That's true for females in our case, but not for males. Male morphological evolution is really more of a consequence of achieving high mating success." In contrast, generation of new species appears to be driven in large part by variations in the environment. Their findings were recently published in Nature Ecology & Evolution.


This map shows the distribution of live-bearing fish throughout North America, Central America and South America. A Kansas State University study has shown that the evolution of female live-bearing fish is influenced more strongly by natural selection while male evolution is influenced more strongly by sexual selection. Image courtesy of Kansas State University.

Lead study author Dr. Tobler stated, "In the big picture, this means that males and females are different and that matters not only within species but also in terms of shaping broad-scale evolutionary outcomes. Acknowledging that the sexes are different really affects how we make inferences about how evolutionary change has actually unfolded."


Kansas State University Press Release

Culumber ZW, Tobler M. Sex-specific evolution during the diversification of live-bearing fishes. Nature Ecology & Evolution. 2017. doi:10.1038/s41559-017-0233-4


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natural selection is not evolution