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Description

<b>Abstract</b><br/>

Studying species interactions at hybrid zones allows biologists to understand the forces that promote speciation. Hybridization among <i>Sphyrapicus nuchalis</i>, <i>S. varius</i>, and <i>S. ruber</i> has long been acknowledged, and hybrid zones between <i>S. nuchalis/S. ruber</i> and <i>S. varius/S. ruber</i> have been characterized with both genetic and genomic data. Using a combination of next-generation Restriction Site-Associated DNA sequencing (RAD-Seq) and traditional genetic methods, we examined patterns of introgression in the poorly characterized <i>S. nuchalis/S. varius</i> contact zone; the two most similar species in the complex, though they are not each other’s closest relatives. We found high introgression rates, with several early and many advanced generation hybrids along a 275 km stretch of Rocky Mountain foothill, pointing to a well-established hybrid zone with hybrid individuals backcrossing with individuals from the parental species and each other. Plumage colouration in the hybrid zone was a relatively poor indicator of parental or hybrid status, which could be attributed to the possible involvement of few large effect genes.</p>; <b>Methods</b><br />

Genetic data were taken from sapsucker blood and tissue samples. These were sequenced using GBS or ddRAD sequencing methods and/or screened at three polymorphic SNP loci. GBS data were processed in Stacks, ddRAD in Tassel, then statistical analyses were performed in R. PCAs were made using scripts (named genomics_r_functions.R) from Irwin, D.E., Alcaide, M., Delmore, K.E., Irwin, J.H., &amp; Owens, G. (2016). Recurrent selection explains parallel evolution of genomic regions of high relative but low absolute differentiation in a ring species. Molecular Ecology, 25(18), 4488–4507.</p>