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

Ecology and Evolution

Huaitong Xu¹  Francine Tremblay¹  Yves Bergeron¹  Véronique Paul¹ 

[1] Chaire Industrielle CRSNG-UQAT-UQAM en Aménagement Forestier Durable, Institut de recherche sur les forêts, Université du Québec en Abitibi-Témiscamingue, Québec, Canada

关键词: Boreal forest;    distribution limit;    genetic diversity;    latitudinal gradient;    microsatellite genotyping;    northern edge;   

DOI  :  10.1002/ece3.371

来源: Wiley

【 摘 要 】

Abstract

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 F_is values and heterozygote deficiency were observed in populations from the marginal (F_is = 0.244; P_HW = 0.0042) and discontinuous zones (F_is = 0.166; P_HW = 0.0042). However, populations from the continuous zone were in HW equilibrium (F_is = −0.007; P_HW = 0.3625). There were no significant latitudinal effects on gene diversity (H_s), allelic richness (AR), or population differentiation (F_st). 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 near-neighbor 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.

【 授权许可】

CC BY-NC   
© 2012 The Authors. Ecology and Evolution published by Blackwell Publishing Ltd.

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