Carnivore contact: a species fracture zone delineated amongst genetically structured North American marten populations (Martes americana and Martes caurina)

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North American martens are forest dependent, influenced by human activity, and climate vulnerable. They have long been managed and harvested throughout their range as the American marten (Martes americana). Recent work has expanded evidence for the original description of two species in North America—M. americana and the Pacific Coast marten, M. caurina—but the geographic boundary between these groups has not been described in detail. From 2010 to 2016 we deployed 734 multi-taxa winter bait stations across a 53,474-km2 study area spanning seven mountain ranges within the anticipated contact zone along the border of Canada and the United States. We collected marten hair samples and developed genotypes for 15 polymorphic microsatellite loci for 235 individuals and, for 175 of those individuals, 493 base-pair sequences of the mtDNA gene COI. Both nuclear and mitochondrial genetic structure identified a sharp break across the Clark Fork Valley, United States, with M. americana and M. caurina occurring north and south of the break, respectively. We estimated global effective population size (Ne) for each mountain range and clinal genetic neighborhood sizes (NS), and we calculated observed (Ho) and expected (He) heterozygosity, fixation index (FST), and clinal measures of allelic richness (Ar), Ho, and inbreeding coefficient (FIS). Despite substantial genetic structure, we detected hybridization along the fracture zone with both contemporary (nuclear DNA) and historic (mtDNA) gene flow. Marten populations in our study area are highly structured, and the break across the fracture zone is the largest documented in North America (FST range 0.21–0.34, mean = 0.27). With the exception of the Coeur d’Alene Mountains, marten were well distributed across higher elevation portions of our sampling area. Clinal NS values were variable suggesting substantial heterogeneity in marten density and movement. For both M. americana and M. caurina, elevationally dependent gene flow and high genetic population structure suggest that connectivity corridors will be important to ensuring long-term population persistence. Our study is an example of how a combination of global and clinal molecular data analyses can provide important information for natural resource management.

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Electronic Files: Zoology: Mammals

Suggested citation: Lucid M, Cushman S, Robinson L, Kortello A, Hausleitner D, Mowat G, Ehlers S, Gillespie S, Svancara LK, Sullivan J, Rankin A and Paetkau D (2020) Carnivore Contact: A Species Fracture Zone Delineated Amongst Genetically Structured North American Marten Populations (Martes americana and Martes caurina). Front. Genet. 11:735. doi: 10.3389/fgene.2020.00735.

In case needed for CSE citation: This research was supported by the following grants: Columbia Basin Trust, Fish and Wildlife Compensation Program, U.S. Fish and Wildlife Service Wildlife and Sport Fish and Restoration Program Competitive State Wildlife Grant (F12AP01101), Idaho Panhandle National Forest (10-CS-11010400-023), U.S. Forest Service Rocky Mountain Research Station (10-JV-11221633-100 & 08-CS-11221633-194), the Wolverine Foundation, Zoo Boise Conservation Fund, and the National Science Foundation (DEB-1457726).
Conflict of Interest: DH was employed by the Seepanee Ecological Consulting Company. AK was employeed by the Grylloblatta Ecological Consulting Company. DP and SG were employed by the company Wildlife Genetics International. LR was employed but they Idaho Department of Fish and Game during the course of this research. However, LR now is employeed by the Rainforest Ecological Consulting Company.
The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.