Influence of northern limit range on genetic diversity and structure in a widespread North American tree, sugar maple (Acer saccharum Marshall)

Due to climate change, the ranges of many North-American tree species are expected to shift northward. Sugar maple (Acer saccharum Marshall) reaches its northern continuous distributional limit in north-eastern North America at the transition between boreal mixed-wood and temperate deciduous forests. We hypothesized that marginal fragmented northern populations from the boreal mixed-wood would have a distinct pattern of genetic structure and diversity. We analyzed 18 microsatellite loci variation in 23 populations distributed along three latitudinal transects (west, central and east) that encompass the continuous-discontinuous species range. Each transect was divided into two zones, continuous (temperate deciduous) and discontinuous (boreal mixed-wood), based on sugar maple stand abundance. Respective positive and negative relationships were found between the distance of each population to the northern limit (D north), and allelic richness (AR) and population differentiation (FST). Thes...