Blind Alleys of Evolution
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Genetic diversity underlies evolutionary potential of species. The distribution and quantity of genetic diversity are profoundly influenced by population structure and breeding system. Strong population subdivision has evolved convergently several times in Anelosimus (Theridiidae) spiders, each time accompanying a switch to permanent social living and inbreeding. Here I use molecular data to (1) establish multiple origins of sociality in spiders, (2) confirm strong matrilineage separation of colonies of the social A. eximius, and (3) demonstrate that the processes of subdivision and inbreeding tend to lead to loss of genetic variability in social spiders. These findings may explain why social lineages seem to diversify little, and exist only briefly.