Introgression between Sphyrapicus nuchalis and S. varius sapsuckers in a hybrid zone in west-central Alberta

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.

Methods

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., & 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.