Posted by Erik Svensson
It is time to kick off the EXEB labmeetings for this coming semester, and what would be better than do it this coming Tuesday (August 18)? Especially when several of us have been to the ESEB Congress and we can have a nice brief discussion about our impressions of where the field of evolutionary biology might be going.
In the same general spirit, I suggest we discuss a paper in Nature from last year on the prospects for group selection in a socially polymorphic spider system. This work has been performed by Jonathan Pruitt and Charles Goodnight, the latter being a long-term champion of group selection.
As group selection has historically been a very controversial topic in evolutionary biology, I hope we will have a stimulating discussion about this paper. See also the "News & Views"-article in the same issue of Nature, which can be found here.
Note different meeting time!
When: Tuesday August 18 at 10.00
Where: "Argumentet", 2nd floor, Ecology Building
Group selection may be defined as selection caused by the differential extinction or proliferation of groups(1,2). The socially polymorphic spider Anelosimus studiosus exhibits a behavioural polymorphism in which females exhibit either a 'docile' or 'aggressive' behavioural phenotype(3,4). Natural colonies are composed of a mixture of related docile and aggressive individuals, and populations differ in colonies' characteristic docile: aggressive ratios(5,6). 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. However, colonies of displaced individuals continued to shift their compositions towards mixtures that would have promoted their survival had they remained at their home sites, regardless of their contemporary environment. Thus, the regulatory mechanisms that colonies use to adjust their composition appear to be locally adapted. Our data provide experimental evidence of group selection driving collective traits in wild populations.