Welcome to the American Ornithological Society 2018 Annual Conference. We are pleased to have you join us at the lovely Hilton El Conquistador Resort in Tucson, AZ.
The Jamaican streamertail hummingbirds (Trochilus polytmus and T. scitulus) represent a potential rare example of avian in-situ speciation to occur on a small oceanic island. These spectacularly plumed island endemics form a narrow hybrid zone where their ranges meet in eastern Jamaica. Streamertail hummingbirds are highly volant, yet bill color, the secondary sexual ornament that distinguishes the taxa, changes from ruby red (T. polytmus) to jet black (T. scitulus) over less than a few kilometers. Previous work to identify targets of selection and reconstruct the evolutionary history for these young lineages has been hampered by the lack of divergence at the majority of loci examined, including the mitochondrial control region, three independently segregating nuclear introns, and six microsatellite loci. Here, I use a genotyping-by-sequencing dataset (6,451 SNPs) to resolve the structure of the hybrid zone and test the prediction that it is a ‘tension zone,' maintained as a balance between selection against hybrids and dispersal into the zone. Using a combination of multivariate and population genetic techniques, I recovered signal for two genetic clusters that match species definitions, and clinal variation in admixture assignments across the island. The range of admixture assignments (0.03 - 93\%) in the hybrid zone populations supports the hypothesis that hybrid zone individuals represent a spectrum of parental types, F1 hybrids, and advanced backcrosses. I discuss the potential drivers of this unusual in-situ speciation event in the larger context of island diversification patterns.
