Aspen Bibliography


Genetic Characterization and Comparison of Three Disjunct Populus tremuloides Michx. (Salicaceae) Stands Across a Latitudinal Gradient

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Natural Resource Report NPS/NRSS/IMD/NRR




National Park Service

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Populus tremuloides has the largest species range of any deciduous tree in North America and is ecologically and economically important. Since the melting of Cordilleran and Laurentide ice sheets, the range of P. tremuloides has expanded northward. With the northward expansion, many areas in western North America that would have been suitable during the early Holocene no longer support P. tremuloides. However, microrefugia still harbor small P. tremuloides stands in ecologically anomalous and spatially disjunct sites across western North America. Theoretical and empirical studies suggest that individuals in such sites may harbor locally adapted genes, having been under strong selection pressure for long periods of time given the more arid environment and presumed relictual origins. Microsatellite markers and a continent-wide dataset for P. tremuloides were employed to compare disjunct stands in three different sites across a latitudinal gradient to assess genetic diversity and possible relictual origins. All disjunct stands were comprised of a single diploid genotype. Each unique diploid genotype contained alleles that were rare and distantly geographically dispersed in the range-wide dataset. This finding suggests that these stands are relictual, i.e. that they are remnants from a time when now broadly separated populations were connected through geneflow. From these findings further detailed study of these and similar stands are needed, as well as in-situ and ex-situ conservation to preserve the genetic resources present in these disjunct stands.