Outnumbered and on others' turf, misfits sometimes thrive

Date: May 31, 2017
Source: University of Texas at Austin

It's hard being a misfit: say, a Yankees fan in a room full of Red Sox fans or a vegetarian at a barbecue joint. Evolutionary biologists have long assumed that's pretty much how things work in nature too. Animals that wander into alien environments, surrounded by better-adapted locals, will struggle. But a team of researchers from The University of Texas at Austin was surprised to find that sometimes, misfits can thrive among their much more numerous native cousins.

"One hundred years of evolutionary theory is built around the idea that immigrants from one population dropped into another population of the same species don't do well," says Daniel Bolnick, a professor of integrative biology and the primary investigator on the study published today in the journal Nature. "Such immigrants are usually rare, and we have found that sometimes their rarity provides a competitive edge."

Bolnick and his team studied a small fish called a three-spined stickleback that lives in the lakes and streams of Vancouver, British Columbia. They studied two populations of the same species: one group that lives in a lake and another group in an adjacent stream.

Evolutionary theory suggests that taking the fish that are adapted to the lake environment and placing them into the stream would put them at a competitive disadvantage compared with the residents. In the dog-eat-dog world of natural selection, outsiders are often poorly adapted to a new environment and less likely to survive or pass on their genes. In the case of the sticklebacks, that's because the lake-adapted fish have different physical traits from their stream-adapted cousins -- such as their overall size, immune traits, body shape and defenses against predators -- that allow them to fare better back home but not necessarily in other environments.



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