Cross‐decades stability of an avian hybrid zone

• DOI: 10.1111/jeb.13524
• Publication Date: 2019-08-20T18:36:37Z
• Authors: Silu Wang; Sievert Rohwer; Kira Delmore; Darren E. Irwin
• Keywords: Hybrid zone; Cline (biology); Plumage; Reproductive isolation; Assortative mating

Abstract Hybrid zones are particularly valuable for understanding the evolution of partial reproductive isolation between differentiated populations. An increasing number hybrid have been inferred to move over time, but in most such cases zone movement has not tested with long‐term genomic data. The Townsend's Warblers ( Setophaga townsendi ) and Hermit S. occidentalis Washington Cascades was previously be moving from northern southwards towards , based on plumage behavioural patterns as well a 2000‐km genetic wake hermit mitochondrial DNA (mtDNA) coastal Warblers. We directly whether position changed 2–3 decades by tracking plumage, mtDNA nuclear variation across two sampling periods (1987–94 2015–16). Surprisingly, there no significant or cline centres time periods. Plumage widths were narrower than expected neutral diffusion, consistent ‘tension zone’ model, which selection against hybrids is balanced parental forms into zone. Our results indicate that this either stable its location at rate detectable decades. Despite considerable gene flow, clines multiple phenotypic genotypic characters suggest evolutionary stability young pair sister species, allowing divergence continue. propose novel biogeographic scenario explain these patterns: rather having moved thousands kilometres current position, inland met Warbler populations along broad front British Columbia Alaska coast hybridization led replacement coastline. Hence, only short distance coast, whereas phenotype appears further south. This case provides an example complex processes distribution phenotypes within among closely related species.