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1 May 2008 Selection and Genomic Differentiation During Ecological Speciation: Isolating the Contributions of Host Association via a Comparative Genome Scan of Neochlamisus bebbianae Leaf Beetles
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Abstract

This study uses a comparative genome scan to evaluate the contributions of host plant related divergent selection to genetic differentiation and ecological speciation in maple- and willow-associated populations of Neochlamisus bebbianae leaf beetles. For each of 15 pairwise population comparisons, we identified “outlier loci” whose strong differentiation putatively reflects divergent selection. Of 447 AFLP loci, 15% were outliers across multiple population comparisons, and low linkage disequilibrium indicated that these outliers derived from multiple regions of the genome. Outliers were further classified as “host-specific” if repeatedly observed in “different-host” population comparisons but never in “same-host” comparisons. Outliers exhibiting the opposite pattern were analogously classified as “host-independent.” Host-specific outliers represented 5% of all loci and were more frequent than host-independent outliers, thus revealing a large role for host-adaptation in population genomic differentiation. Evidence that host-related selection can promote divergence despite gene flow was provided by population trees. These were structured by host-association when datasets included host-specific outliers, but not when based on neutral loci, which united sympatric populations. Lastly, three host-specific outliers were highly differentiated in all nine different-host comparisons. Because host-adaptation promotes reproductive isolation in these beetles, these loci provide promising candidate gene regions for future molecular studies of ecological speciation.

Scott P. Egan, Patrik Nosil, and Daniel J. Funk "Selection and Genomic Differentiation During Ecological Speciation: Isolating the Contributions of Host Association via a Comparative Genome Scan of Neochlamisus bebbianae Leaf Beetles," Evolution 62(5), 1162-1181, (1 May 2008). https://doi.org/10.1111/j.1558-5646.2008.00352.x
Received: 17 September 2007; Accepted: 23 January 2008; Published: 1 May 2008
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