Data from: Population structure over a broad spatial scale driven by non-anthropogenic factors in a wide-ranging migratory mammal, Alaskan caribou

Wide-ranging mammals face significant conservation threats, and knowledge
of the spatial scale of population structure and its drivers is needed to
understand processes that maintain diversity in these species. We analysed
DNA from 655 Alaskan caribou (Rangifer tarandus granti) from 20 herds that
vary in population size, used 19 microsatellite loci to document genetic
diversity and differentiation in Alaskan caribou, and examined the extent
to which genetic differentiation was associated with hypothesized drivers
of population subdivision including landscape features, population size
and ecotype. We found that Alaskan caribou are subdivided into two
hierarchically structured clusters: one group on the Alaska Peninsula
containing discrete herds and one large group on the Mainland lacking
differentiation between many herds. Population size, geographic distance,
migratory ecotype and the Kvichak River at the nexus of the Alaska
Peninsula were associated with genetic differentiation. Contrary to
previous hypotheses, small Mainland herds were often differentiated
genetically from large interconnected herds nearby, and genetic drift
coupled with reduced gene flow may explain this pattern. Our results raise
the possibility that behaviour helps to maintain genetic differentiation
between some herds of different ecotypes. Alaskan caribou show remarkably
high diversity and low differentiation over a broad geographic scale.
These results increase information for the conservation of caribou and
other migratory mammals threatened by population reductions and landscape
barriers and may be broadly applicable to understanding the spatial scale
and ecological drivers of population structure in widespread species.