Michael Tobler, associate professor of biology at K-State, and Zach Culumber, a former K-State postdoctoral research associate, found that female evolution in the Poeciliidae family of fish was influenced more strongly by natural selection and the environment, while male evolution was influenced more by sexual selection — characteristics that females find desirable or that makes them superior competitors — according to a news release from the university.
Catchy title, huh?
“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,” Tobler said in the news release. “Acknowledging that the sexes are different really affects how we make inferences about how evolutionary change has actually unfolded.”
While most fish breed through eggs laid by females, species such as mollies, platies, guppies, swordtails and mosquitofish retain their eggs and give birth to live young the way mammals do.
The only member of the Poeciliidae family that is native to Kansas is the Western mosquitofish, according to the Kansas Department of Wildlife, Parks and Tourism. The fish is small, dull gray or brown in color with no bars of bands on the sides, and has a rounded tail. The U.S. Geological Survey notes its native range extends through much of Kansas, mainly the northeastern and southern parts of the state.
While these may not be game fish, as an outdoors enthusiast I always find it interesting to learn about the types of fish in Kansas streams.
“When we analyzed males and females separately, we got completely different answers,” Tobler said in the release. “When we averaged males and females, it was not at all reflective of how the males or the females evolve. We can’t just lump the sexes together because it misrepresents how evolution has proceeded across this family of fish.”
The release added that the researchers are planning future studies with live male and female fish to better understand the changes that have occurred during 60 million years of evolution.
“Although we have long believed that sexual selection is an important force in the evolution of live-bearing fishes, and our data suggest that this is true for male body shape, it seems that geographic variation in the environment may have been more important for stimulating the formation of new species of live-bearing fishes,” Culumber said in the release.