GENOMIC MAPPING OF REPRODUCTIVE
ISOLATION IN THE LARCH BUDMOTH, ZEIRAPHERA DINIANA
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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