Distribution of American pine marten (Martes americana & M. caurina)

The occurrence of two distinct species of pine marten in North America was generally recognized prior to the work of Wright (1953). He reported evidence of individuals with intermediate morphology, concluded that the two forms were interbreeding, and therefore relegated caurina to subspecies status within americana; this usage has been followed ever since. However, genetic evidence identifies subspecies of americana and caurina as distinct maternal lineages, which may therefore be considered good 'phylogenetic' species. The genetic analysis supports the hypothesis that the two North American subspecies groups should once again be considered two distinct species: Martes americana (Turton, 1806) in the east and north, and Martes caurina (Merriam, 1890) in the west, respectively. [after Carr & Hicks 1997]