Persistence of genetic variation in recolonized Tsuga canadensis (Eastern hemlock) populations following historic forest clearance

The recovery of genetic variation in newly recolonized populations is an important concern in forest conservation genetics. We examined the potential recovery of genetic diversity and changes to genetic structure in populations of the wind-pollinated species Tsuga canadensis that naturally regenerated following the extensive 19th century regional forest clearance for agriculture in west-central Massachusetts. We genotyped 264 individuals across six microsatellite loci and compared levels and patterns of genetic variation between primary forests (forests that were logged but never cleared) and secondary forests (stands that were recolonized following agricultural abandonment). We found no significant reductions in genetic diversity in secondary forests (A_R=5.450; H_S=0.718) compared to primary forests (A_R=5.742; H_S=0.730). Moreover, the population genetic differentiation was also not significantly reduced in secondary compared to primary forests, with no significant genetic structure observed among all populations. These results suggest rapid genetic recovery of T.canadensis populations in recolonized forests compared with other late-successional temperate tree species.