Genetic consequences of fragmentation in “arbor vitae,” eastern white cedar (Thuja occidentalisL.), toward the northern limit of its distribution range


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Xu, Huaitong, Tremblay, Francine, Bergeron, Yves, Paul, Véronique et Chen, Cungen (2012). Genetic consequences of fragmentation in “arbor vitae,” eastern white cedar (Thuja occidentalisL.), toward the northern limit of its distribution range. Ecology and Evolution , 2 (10). pp. 2506-2520. doi:10.1002/ece3.371 Repéré dans Depositum à

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We tested the hypothesis that marginal fragmented populations of eastern white cedar (EWC) are genetically isolated due to reduced pollen and gene flow. In accordance with the central-marginal model, we predicted a decrease in population genetic diversity and an increase in differentiation along the latitudinal gradient from the boreal mixed-wood to northern coniferous forest. A total of 24 eastern white cedar populations were sampled along the north-south latitudinal gradient for microsatellite genotyping analysis. Positive Fis values and heterozygote deficiency were observed in populations from the marginal (Fis = 0.244; PHW = 0.0042) and discontinuous zones (Fis = 0.166; PHW = 0.0042). However, populations from the continuous zone were in HW equilibrium (Fis = -0.007; PHW = 0.3625). There were no significant latitudinal effects on gene diversity (Hs), allelic richness (AR), or population differentiation (Fst). Bayesian and NJT (neighbor-joining tree) analyses demonstrated the presence of a population structure that was partly consistent with the geographic origins of the populations. The impact of population fragmentation on the genetic structure of EWC is to create a positive inbreeding coefficient, which was two to three times higher on average than that of a population from the continuous zone. This result indicated a higher occurrence of selfing within fragmented EWC populations coupled with a higher degree of gene exchange among nearneighbor relatives, thereby leading to significant inbreeding. Increased population isolation was apparently not correlated with a detectable effect on genetic diversity. Overall, the fragmented populations of EWC appear well-buffered against effects of inbreeding on genetic erosion.

Type de document: Article
Informations complémentaires: Licence d'utilisation : CC-BY-NC 4.0
Mots-clés libres: Boreal forest; Distribution limit; Genetic diversity; Latitudinal gradient; Microsatellite genotyping; Northern edge
Divisions: Forêts
Date de dépôt: 22 avr. 2020 15:59
Dernière modification: 08 mai 2020 16:08

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