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Title: History, geography and host use shape genomewide patterns of genetic variation in the redheaded pine sawfly ( Neodiprion lecontei )

Divergent host use has long been suspected to drive population differentiation and speciation in plant‐feeding insects. Evaluating the contribution of divergent host use to genetic differentiation can be difficult, however, as dispersal limitation and population structure may also influence patterns of genetic variation. In this study, we use double‐digest restriction‐associatedDNA(ddRAD) sequencing to test the hypothesis that divergent host use contributes to genetic differentiation among populations of the redheaded pine sawfly (Neodiprion lecontei), a widespread pest that uses multiplePinushosts throughout its range in eastern North America. Because this species has a broad range and specializes on host plants known to have migrated extensively during the Pleistocene, we first assess overall genetic structure using model‐based and model‐free clustering methods and identify three geographically distinct genetic clusters. Next, using a composite‐likelihood approach based on the site frequency spectrum and a novel strategy for maximizing the utility of linkedRADmarkers, we infer the population topology and date divergence to the Pleistocene. Based on existing knowledge ofPinusrefugia, estimated demographic parameters and patterns of diversity among sawfly populations, we propose a Pleistocene divergence scenario forN. lecontei. Finally, using Mantel and partial Mantel tests, we identify a significant relationship between genetic distance and geography in all clusters, and between genetic distance and host use in two of three clusters. Overall, our results indicate that Pleistocene isolation, dispersal limitation and ecological divergence all contribute to genomewide differentiation in this species and support the hypothesis that host use is a common driver of population divergence in host‐specialized insects.

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Journal Name:
Molecular Ecology
Page Range / eLocation ID:
p. 1022-1044
Medium: X
Sponsoring Org:
National Science Foundation
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