Principal Investigator: James Mallet
Postdoc: Igor Emelianov
Collaborators: Dr. Werner Baltensweiler, Zürich; Dr. Christer Löfstedt, Lund University; Frantisek Marec, Czech Academy of Sciences
PhD student: Michele Drès

Department of Biology, University College London, 4 Stephenson Way, LONDON NW1 2HE

This study uses genomic and experimental approaches to analyse a pair of incipient species, the larch- and pine-feeding host races of the moth Zeiraphera diniana (Tortricidae).  In spite of appreciable natural hybridization between host races of these two forms, about a tenth of all loci scattered across 28 chromosomes are strongly differentiated.  In addition, we have used field work and laboratory experiments to show that the hybridisation rates are expected to be around 3% per generation in the wild.  A major prediction of such incipient species under under divergent selection is a mosaic genomic pattern of differentiation.  Using, among others, a recently invented technique (AFLP), we show, for the first time, that the prediction of a mosaic genome is upheld. Most of the genome, including the lepidopteran W sex chromosome and the mitochondrial genome, show little or no differentiation, but 4-6 chromsomes differ strongly and at multiple AFLP markers between the host races.

These results give an important case of a system in which adaptive differences are maintained in the face of gene flow.  The results will help in  understanding similar systems of great economic importance, for example endangered species exposed to the threat of hybridisation from alien relatives, crop pests exposed to patchworks of crops (including those with pesticide treatments, or with transgenic pesticidal properties) and refugia of wild hosts, and transgenic constructs of pests of human health, such as mosquitoes engineered to be refractory to malaria susceptibility.

Full report

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