Data from: Isolation by environment in white-breasted nuthatches (Sitta carolinensis) of the Madrean Archipelago sky islands: a landscape genomics approach

Understanding landscape processes driving patterns of population genetic
differentiation and diversity has been a long-standing focus of ecology
and evolutionary biology. Gene flow may be reduced by historical,
ecological or geographic factors, resulting in patterns of isolation by
distance (IBD) or isolation by environment (IBE). Although IBE has been
found in many natural systems, most studies investigating patterns of IBD
and IBE in nature have used anonymous neutral genetic markers, precluding
inference of selection mechanisms or identification of genes potentially
under selection. Using landscape genomics, the simultaneous study of
genomic and ecological landscapes, we investigated the processes driving
population genetic patterns of White-breasted Nuthatches (Sitta
carolinensis) in sky islands (montane forest habitat islands) of the
Madrean Archipelago. Using more than 4000 single nucleotide polymorphisms
and multiple tests to investigate the relationship between genetic
differentiation and geographic or ecological distance, we identified IBE,
and a lack of IBD, among sky island populations of S. carolinensis. Using
three tests to identify selection, we found 79 loci putatively under
selection; of these, seven matched CDS regions in the Zebra Finch. The
loci under selection were highly associated with climate extremes (maximum
temperature of warmest month and minimum precipitation of driest month).
These results provide evidence for IBE – disentangled from IBD – in sky
island vertebrates and identify potential adaptive genetic variation.