Abstract
Local adaptation frequently occurs across populations as a result of migration-selection balance between divergent selective
pressures and gene flow associated with life in heterogeneous landscapes. Studying the effects of selection and gene flow on
the adaptation process can be achieved in systemsthat have recently colonized extremeenvironments. This study utilizes an endemic
South American duck species, the speckled teal (Anas flavirostris),which has both high- and low-altitude populations. High-altitude
speckled teal (A. f. oxyptera) are locally adapted to the Andean environment and mostly allopatric from low-altitude birds (A. f.
flavirostris);however, there is occasional geneflowacross altitudinal gradients. In this study,we used next-generation sequencing to
explore genetic patterns associated with high-altitude adaptation in speckled teal populations, as well as the extent to which the
balance between selection and migration have affected genetic architecture. We identified a set of loci with allele frequencies
strongly correlated with altitude, including those involved in the insulin-like signaling pathway, bone morphogenesis, oxidative
phosphorylation, responders to hypoxia-induced DNAdamage, and feedback loops to the hypoxia-inducible factor pathway. These
same outlier loci were found to have depressed gene flow estimates, as well as being highly concentrated on the Z-chromosome.
Our results suggest a multifactorial response to life at high altitudes through an array of interconnected pathways that are likely
under positive selection and whose genetic components seem to be providing an effective genomic barrier to interbreeding,
potentially functioning as an avenue for population divergence and speciation
Peer reviewed