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Mutual intra- and interspecific social parasitism between parapatric sister species of Vespula wasps

Saga, T., Kanai, M., Shimada, M., Okada, Y.
Insectes sociaux 2017 v.64 no.1 pp. 95-101
Vespula, alloparental behavior, allopatric speciation, animal breeding, hosts, parasites, social insects, social parasitism, social structure, sympatric speciation, yellowjackets, Japan
Cooperative breeding of animals is vulnerable to social parasitism, in which parasites usurp the labors of the hosts. In social hymenopterans, social parasitism has evolved numerous times independently, and the process by which it has arisen is thus a major question in evolutionary biology. It is generally thought that parasites originate from their hosts via sympatric speciation, and some actual examples have been reported. On the other hand, an alternative hypothesis that allopatric speciation first occurred, and then one species subsequently evolved as the parasite of its sister species has been theoretically supported, but no actual cases have yet been reported. Here, we report that our observations suggest facultative, temporary, and mutual social parasitism that occurs in both an intra- and interspecific manner in two sister species of yellow jackets, Vespula flaviceps and V. shidai, in Japan. Considering their parapatric distribution, social structure, and parasitic behaviors, social parasitism between these two species does not follow the conventional sympatric speciation hypothesis (intraspecific hypothesis), but possibly supports the social deception hypothesis (interspecific hypothesis). The mutual social parasitism between parapatric sister species offers a good opportunity to study the evolution of social parasitism.