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

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 https://depositum.uqat.ca/id/eprint/1052

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Résumé

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
URI:	https://depositum.uqat.ca/id/eprint/1052

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