Pliocene-early Pleistocene geological events structure Pacific martens (Martes caurina)

The complex topography, climate and geological history of Western North
America has shaped contemporary patterns of biodiversity and species
distributions in the region. Pacific martens (Martes caurina) are
distributed along the northern Pacific Coast of North America with
disjunct populations found throughout the Northwestern Forested Mountains
and Marine West Coast Forest ecoregions of the West Coast. Martes in this
region have been classified into subspecies; however, the subspecific
designation has been extensively debated. In this study, we use genomic
data to delineate conservation units of Pacific marten in the
Sierra-Cascade-Coastal montane belt in the Western United States. We
analyzed the mitochondrial genome for 94 individuals to evaluate the
spatial distribution and divergence times of major lineages. We further
genotyped 401 individuals at 13 microsatellite loci to investigate major
patterns of population structure. Both nuclear and mitochondrial DNA
suggest substantial genetic substructure concordant with historical
subspecies designations. Our results revealed that the region contains two
distinct mitochondrial lineages: a Cascades/Sierra lineage that diverged
from the Cascades/coastal lineage 2.23 (1.48-3.14 MYA), consistent with
orogeny of the Cascade Mountain chain. Interestingly, Pacific Martes share
phylogeographic patterns similar with other sympatric taxa, suggesting the
complex geological history has shaped the biota of this region. The
information is critical for conservation and management efforts and
further investigation of adaptive diversity is warranted following
appropriate revision of conservation management designations.