Genetic and phenotypic divergence between low- and high-altitude populations of two recently diverged cinnamon teal subspecies

Spatial variation in the environment can lead to divergent selection between populations occupying different parts of a species’ range, and ultimately lead to population divergence. The colonization of new areas can thus facilitate divergence in beneficial traits, yet with little differentiation at neutral genetic markers. We investigated genetic and phenotypic patterns of divergence between low- and high-altitude populations of cinnamon teal inhabiting normoxic and hypoxic regions in the Andes and adjacent lowlands of South America. Cinnamon Teal showed strong divergence in body size (PC1; PST = 0.56) and exhibited significant frequency differences in a single non-synonymous α-hemoglobin amino acid polymorphism (Asn/Ser-α9; FST = 0.60) between environmental extremes, despite considerable admixture of mtDNA and intron loci (FST = 0.004–0.168). Inferences of strong population segregation were further supported by the observation of few mismatched individuals in either environmental extre...