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New study provides evidence of group selection theory

Posted November 10, 2014

A new study conducted by American biologists provides theory group selection with compelling empirical support. Idea that evolution selects not only against genes or individuals, but against groups as well were almost universally refused during the second part of the twentieth century. However, it can be that this theory was refuted too early.

Picture: Spiders Web. Image credit: A Bremner via Flickr, CC BY 2.0.

Picture: Spiders Web. Image credit: A Bremner via Flickr, CC BY 2.0.

“Our data provide experimental evidence of group selection driving collective traits in wild populations,” Jonathan N. Pruitt and Charles J. Goodnight at the University of Pittsburgh say.

“In societies in which individual fitness is tightly linked with the performance of the group, the theory of group selection predicts that evolution will favour traits in individuals that aid in maximizing their group’s success—which, in turn, are predicted to increase individuals’ long-term evolutionary interests,” authors of the study published in Nature explain.

This intuition is very powerful and even Charles Darwin endorsed this view. However, group selection usually was a matter of theoretical speculations, but had weak empirical support. In addition, it was heavily criticized by such famous theorists as Richard Dawkins who advocated gene-centered version of evolution. He and his colleagues argue that genes are the only units of natural selection.

Nevertheless, presence of group selection was demonstrated by some recent studies which were carried out under laboratory conditions. Pruitt and Goodnigt present first evidence of group selection in a natural setting. They explored, how species of spiders called Anelosimus studiosus adapt to their local environment. These insects lives in groups containing two types of individuals: docile and aggressive. It is known that this trait is phenotypic and heritable.

“Using experimentally constructed colonies of known composition, here we demonstrate that population-level divergence in docile: aggressive ratios is driven by site-specific selection at the group level—certain ratios yield high survivorship at some sites but not others. Our data also indicate that colonies responded to the risk of extinction: perturbed colonies tended to adjust their composition over two generations to match the ratio characteristic of their native site, thus promoting their long-term survival in their natal habitat,” the researchers claim.

Article: Pruit N. J., Goodnight C. J., 2014, Site-specific group selection drives locally adapted group compositions, Nature 514, 359–362, source link.

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