MIRAGES AND FLIES IN THE DESERT – HOW REAL ARE SPECIATION ISLANDS?

A large number of recent genome scans have interpreted outliers of increased divergence (usually measured via Fst) between closely related species as “speciation islands”. I describe a more powerful approach for scanning genomic data which models the distribution of blockwise configurations of mutations along the genome conditional on an explicit demography of divergence and gene flow. I illustrate the new method on whole genome data for a pair of recently diverged host races of cactophilic Drosophila. While a standard Fst scan does not diagnose any outliers, the new method detects an enrichment for regions of reduced effective gene flow and shows that these are clustered over a range of scales.

The Lohse lab is interested in the fundamental forces of evolution and how these interact to generate and maintain genomic - and ultimately phenotypic – variation. Our theoretical work uses coalescent theory to develop new methods for inferring past demographic and selective events from genome data. We apply these modelling approaches sequence data from natural Insect populations to learn about the speciation process.

[Host: Martim Melo, Population Genetics, Hybridization and Speciation]

Image credits: desert landscape - WikiCommons