Landscape genetics of fishers (Martes pennanti) in the Northeast: dispersal barriers and historical influences.

Habitat fragmentation and overtrapping are thought to have resulted in severe population declines for fisher (Martes pennanti) across the northeastern United States, and by the end of the 1930s only 3 remnant populations remained. Subsequent trapping cessation, extensive reintroduction programs, and natural recolonization have helped fishers to reclaim much of their historical range. The degree to which these processes have impacted genetic structure in this species, however, remains unknown. We used 11 microsatellites from tissue samples (n = 432) of fishers to characterize contemporary population structure in light of historical population structure and thus to determine the relative influence of anthropogenic disturbances and natural landscape features in shaping genetic structure of the contemporary population. Our results indicated that 3 well-differentiated contemporary populations are present that correspond well with what would be expected based on their reported history. A course barrier to dispersal appears in the western portion of the study area associated with several lakes including Lake George and Great Sacandaga Lake. Large-scale reintroduction efforts and natural recolonizations have largely had predictable impacts on population structure. An important exception is the substantial impact of the reintroduction of fishers to Vermont.