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Title: Reproductive isolation between host races of Phytomyza glabricola on Ilex coriacea and I. glabra

item HEBERT, J. - University Of Maryland
item Scheffer, Sonja
item HAWTHORNE, D. - University Of Maryland

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2013
Publication Date: 9/18/2013
Publication URL:
Citation: Hebert, J.B., Scheffer, S.J., Hawthorne, D.J. 2013. Reproductive isolation between host races of Phytomyza glabricola on Ilex coriacea and I. glabra. PLoS One. 8:1-6.

Interpretive Summary: Leafmining flies are important invasive pests of vegetables, ornamentals, and cut flower crops around the world, causing millions of dollars in losses. The leafmining fly Phytomyza glabricola feeds on two species of holly, but molecular data show that this fly species is comprised of two morphologically cryptic species each feeding on its own species of holly. Behavioral mating trials with flies from the two hosts confirm significant reproductive isolation. This information will be of interest to growers of hollies, pest managers, and scientists.

Technical Abstract: Recently diverged taxa often show discordance in genetic divergence among genomic loci, where some loci show strong divergence and others show none at all. Genetic studies alone cannot distinguish among the possible mechanisms but experimental studies on other aspects of divergence may provide guidance in the inference of causes of observed discordances. In this study, we used no-choice mating trials to test for the presence of reproductive isolation between host races of the leaf-mining fly, Phytomyza glabricola on its two holly host species, Ilex coriacea and I. glabra. These trials inform our effort to determine the cause of significant differences in the degree of divergence of nuclear and mitochondrial loci of flies collected from the two host plants. We present evidence of reproductive isolation between host races in a controlled greenhouse setting: significantly more mate pairs consisting of flies from the same host plant species produced offspring than across-host mate pairs, which produced no offspring. We also tested whether the presence of the natal or non-natal host plant affects reproductive success. Flies collected from I. coriacea were more likely to produce offspring when in the presence of the natal host, whereas the presence or absence of either the natal or non-natal host had no effect on flies collected from I. glabra. The results indicate discordant patterns of nuclear and mitochondrial divergence among host races of P. glabricola is likely due to incomplete lineage sorting, and the host races may be well on their way to becoming biological species.