American marten (Martes americana) COSEWIC assessment and status report: chapter 4

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Species Information

Name and classification

The recognition of subspecies of American marten, Martes americana, based on morphological data remains tentative and controversial. Hall (1981) distinguished 14 subspecies; including M. americana atrata, a subspecies endemic to Newfoundland. Other authors argued that the partitioning of subspecies was arbitrary and subject to error based on small sample sizes or samples biased by sex or coat colour variation (Hagmeier 1958, 1961; Anderson 1970; Clark et al. 1987). Hagmeier (1958, 1961) and Clark et al. (1987) recognize M. americana atrata as the Newfoundland subspecies, but include M. americana brumalis, found in northen Quebec and Labrador, as a synonym. The subspecies of American marten have not been reviewed vis-à-vis recent studies showing genetic uniqueness from mainland populations.

Morphological description

The American marten is a long, slender arboreal weasel with short limbs, broad feet and semi-retractable claws used for climbing. The head is broad, tapering to a sharp nose and the ears are large and rounded. Its bushy tail is about ½ of the body length. The long, silky, dense fur varies from pale buff, to dark brown dorsally. A bib on the throat and chest may be creamy to bright orange. Males are about 15% longer than females and up to 65% heavier.

Martes americana atrata, found in Newfoundland, Labrador and northern Quebec (Figure 1) is a large, dark race (Hagmeier 1961) compared with the small pale form to the south and west (M. americana americana). The subspecies, and the population in Newfoundland, are comparatively large, with mean weights for males of up to 1,325 g. (Bissonette et al. 1988, Smith and Schaefer 2002, Hearn et al. 2005).

Genetic description

Carr and Hicks (1997) showed no divergence of the Newfoundland marten from most mainland populations of the americana group based on the cytochrome b gene of mtDNA. However, in microsatellite DNA (Kyle and Strobeck 2003), and to some extent in randomly amplified polymorphic DNA (McGowan et al. 1999), the Newfoundland population is genetically distinct from mainland marten populations of the americana group, which shows relative homogeneity, suggesting genetic connectivity, across Canada (Kyle and Strobeck 2003). The genetic variation of Newfoundland marten is significantly lower than that of mainland populations (McGowan et al. 1999, Kyle and Strobeck 2003). The average expected heterozygosity (H_E) of the Newfoundland population was 40.2% vs. 63.6% averaged for 24 mainland populations from across Canada (Kyle and Strobeck 2003).

Low genetic diversity and divergence from mainland populations are consistent with genetic drift and the absence of immigration as a result of isolation since the last ice age. Recent population declines may further decrease genetic variation on the island. The population introduced in the Main River watershed from other parts of Newfoundland shows lower genetic diversity than other populations on the island (M. McGrath, pers. comm., 2007) as a possible founder effect and indicator of isolation. The Newfoundland population of American marten is designatable on the basis of genetic and ecological distinctiveness (Green 2005).