Abstract
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 northeastern 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 variation at 18 microsatellite loci from 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 (A R) and population differentiation (F ST). These relations were tested for each transect separately; the pattern (discontinuous–continuous) remained significant only for the western transect. structure analysis revealed the presence of four clusters. The most northern populations of each transect were assigned to a distinct group. Asymmetrical gene flow occurred from the southern into the four northernmost populations. Southern populations in Québec may have originated from two different postglacial migration routes. No evidence was found to validate the hypothesis that northern populations were remnants of a larger population that had migrated further north of the species range after the retreat of the ice sheet. The northernmost sugar maple populations possibly originated from long‐distance dispersal.
Highlights
The last glacial maximum (LGM) occurred about 21,000 years before present (-year BP) and was the coldest period in recent climatic history (Jackson et al, 2000)
“range shift following the last glacial maximum” hypothesis proposes that the patterns of genetic diversity in leading edge populations are influenced by past climate-driven range dynamics rather than by demographic and evolutionary processes that are predicted in the central–marginal model (Hampe & Petit, 2005)
Wind-pollinated tree species may be buffered against the effect of fragmentation on the genetic structure of peripheral populations due to long-distance gene flow that contributes to a decrease in differentiation among populations (Kremer et al, 2012)
Summary
The last glacial maximum (LGM) occurred about 21,000 years before present (-year BP) and was the coldest period in recent climatic history (Jackson et al, 2000). We foresee the northern range expansion of several species (Iverson, Prasad, Matthews, & Peters, 2008) This shift in range could be marked in peripheral populations located along their distribution edge (Iverson, Schwartz, & Prasad, 2004). The central–marginal hypothesis predicts that those patterns of genetic diversity and structure are the consequences of ecological marginality in populations found at the periphery of the species range compared to core populations (Eckert et al, 2008). “range shift following the last glacial maximum” hypothesis proposes that the patterns of genetic diversity in leading edge (i.e., colonizing front) populations are influenced by past climate-driven range dynamics rather than by demographic and evolutionary processes that are predicted in the central–marginal model (Hampe & Petit, 2005). Wind-pollinated tree species may be buffered against the effect of fragmentation on the genetic structure of peripheral populations due to long-distance gene flow that contributes to a decrease in differentiation among populations (Kremer et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
