Large-scale forest clearance for agriculture had occurred following the European settlement starting in the 1600s, followed by forest regeneration as these lands were abandoned in the mid-1800s (Figure 1). In New England, these caused massive population declines, then regeneration, in disturbance-sensitive species such as American beech and Eastern hemlock. Such demographic shifts impacts genetic diversity of populations. The magnitude of these impacts can be more pronounced in smaller populations at marginal habitat.
I investigated how habitat characteristics influence genetic impacts of 19th century large-scale demographic declines on two tree species using population genetics. I found that habitat characteristics influence the magnitude of the negative impact of population declines as genetic divergence increases in marginal populations but not in core populations (Lumibao et al. 2014 J Hered; 2015 Plant Species Biol). These results suggest that, even within a species, populations respond in their own idiosyncratic way, illustrating the need to account for habitat differences when assessing the genetic consequences of forest fragmentation.