Submitted to: Journal of Evolutionary Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/10/2013
Publication Date: 3/20/2013
Citation: Forbes, A.A., Rice, L.A., Stewart, N.B., Yee, W.L., Neiman, M. 2013. Niche differentiation and colonization of a novel environment by an asexual wasp. Journal of Evolutionary Biology. DOI:10.1111/jeb.12135. Interpretive Summary: The western cherry fruit fly damages sweet cherry fruit and is a pest of domesticated cherries in the western U.S. Despite its pest status, little is known about the natural enemies of the fly. Personnel at the University of Iowa and the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA determined if an asexual wasp that evolved with and attacks flies in wild cherries has adapted to flies in domesticated cherries, which is a new host. It was found that a group of wasps with distinctive genetics emerged earlier than other groups of wasps and that these wasps were strongly associated with early-emerging flies in domesticated cherries, respectively. This result is novel and suggests that asexual wasps, despite reduced genetic variation, are able to adapt to new hosts and habitats through as yet unknown mechanisms.
Technical Abstract: How do asexual taxa persist despite changing environmental conditions, and how do they adapt to novel environments? These questions are linked by their mutual focus on the relationship between genetic variation, which is often limited in asexuals, and the ability to respond to environmental change. Here, we show that genetic variation between different lineages of the asexual parasitic wasp Diachasma muliebre is associated with variation in its life history phenology. These wasps are univoltine, short-lived as adults, and parasitize hosts that occur during a short temporal window. Individual wasps possessing a single distinctive mitochondrial haplotype emerged as adults significantly earlier than other wasps at each site where they were collected. This lineage therefore occupies a discrete slice of the overall temporal niche occupied by the species. Additionally, this early-emerging lineage of D. muliebre is one of two lineages that have colonized a novel habitat with an earlier seasonal availability. AFLP markers demonstrate much-reduced genetic variation among D. muliebre compared with its sexual relatives, supporting a hypothesis that genetic and phenotypic variation have evolved following a single origin of asexuality. Taken together, these results suggest that asexual taxa may colonize and adapt to new niches via preadaptation, mutation, and/or natural selection.