Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2009
Publication Date: 2/7/2009
Citation: Galbreath, J.G., Smith, J.E., Becnel, J.J., Butlin, R.K., Dunn, A.M. 2009. Reduction in post-invasion genetic diversity in Crangonyx pseudogracilis (Amphipoda: Crustacea): a genetic bottleneck or the work of hitchhiking vertically transmitted microparasites?. Biological Invasions.Available: http://www.springerlink.com/content/yw707p5637117095/fulltext.html. Interpretive Summary: Naturally occurring protozoan parasites (Microsporidia) of insects are under study to evaluate and develop these disease causing organisms as biological control agents. Microsporidian parasites are known to cause mortality in arthropods worldwide, but fundamental knowledge on their life cycles, modes of transmission and methods for identification is presently incomplete. This investigation examines the implications for microsporidia and the successful establishment of invasive species. New information obtained here contributes to our basic understanding of these parasites which will assist in the evaluation and development of microsporidia as biocontrol agents.
Technical Abstract: Enemy release has been proposed as a major factor in invasion success. However, as invading hosts and parasites may be derived from a small subset of genotypes it is important to test this hypothesis in the context of host population genetics. We demonstrate that invasive populations of the North American crustacean Crangonyx pseudogracilis are less diverse than the natives and are derived from a single source. Despite this restriction in host genetic diversity we find no evidence for enemy release when comparing parasite diversity of hosts in the invasive range with that of the source population. A single, vertically transmitted, microsporidian sex ratio distorter dominates the parasite assemblage in the invasive range. This supports the prediction that vertically transmitted parasites may evade the stochastic processes and selective pressures leading to enemy release. We further propose that parasite sex ratio distortion may facilitate host invasion success.