Canada Research Chair in Forest and Conservation Genomics and Biotechnology, Canadian Genomics and Conservation Genetics Institute, Faculty of Forestry and Environmental, Management, University of New Brunswick, 28 Dineen Drive, Fredericton, New Brunswick, Canada.
Am J Bot. 2012 Apr;99(4):690-9. doi: 10.3732/ajb.1100116. Epub 2012 Apr 2.
Geographically peripheral (marginal) populations are expected to have lower genetic diversity and higher genetic differentiation than geographically core (central) populations as a result of supposedly lower effective population size (N(e)) and higher genetic drift, founder effect, fragmentation, and isolation in peripheral than in core populations. Here we address this issue for a long-lived plant species, eastern white cedar (Thuja occidentalis).
Genetic diversity and population structure of 13 natural populations of eastern white cedar from its Canadian eastern peripheral and core natural ranges in New Brunswick, Nova Scotia, and Prince Edward Island were studied using six nuclear microsatellite DNA markers.
The core populations of eastern white cedar had significantly higher allelic diversity (mean A = 8.83, A(r) = 8.13, A(e) = 4.03) and N(e) (428) than the peripheral populations (A = 6.64, A(r) = 6.15, A(e) = 3.12, N(e) = 198). However, expected heterozygosity was similar in the core (H(e) = 0.64) and peripheral (H(e) = 0.60) populations. Genetic differentiation was significantly higher among the peripheral (F(ST) = 0.089) than among the core (F(ST) = 0.032) populations. No genetic differentiation (F(ST)/Φ(RT) = 0.000) was detected between core and peripheral regions.
Peripheral populations have significantly lower N(e) and genetic diversity in terms of allelic diversity (richness) and significantly higher genetic differentiation than the core populations of eastern white cedar in its Canadian eastern range. However, core and peripheral populations have similar levels of expected heterozygosity. Implications for conservation of eastern white cedar genetic resources are discussed.
由于地理上边缘（外围）种群的有效种群大小（N(e)）较低，遗传漂变、奠基者效应、碎裂和隔离的影响较大，因此与地理中心（核心）种群相比，其遗传多样性较低，遗传分化程度较高。本研究以一种长寿植物——东方雪杉（Thuja occidentalis）为例，探讨了这一问题。
本研究利用 6 个核微卫星 DNA 标记，对来自加拿大东部边缘和新不伦瑞克省、新斯科舍省和爱德华王子岛核心自然区域的 13 个东方雪杉天然种群的遗传多样性和种群结构进行了研究。
东方雪杉核心种群的等位基因多样性（平均值 A = 8.83，A(r) = 8.13，A(e) = 4.03）和 N(e)（428）显著高于边缘种群（A = 6.64，A(r) = 6.15，A(e) = 3.12，N(e) = 198）。然而，核心和边缘种群的预期杂合度相似（H(e) = 0.64 和 H(e) = 0.60）。边缘种群的遗传分化显著高于核心种群（F(ST) = 0.089 和 F(ST) = 0.032）。核心和边缘地区之间未检测到遗传分化（F(ST)/Φ(RT) = 0.000）。
在加拿大东部地区，与核心种群相比，东方雪杉的边缘种群的 N(e)和遗传多样性（以等位基因多样性和丰富度衡量）显著较低，遗传分化程度显著较高。然而，核心和边缘种群的预期杂合度水平相似。讨论了保护东方雪杉遗传资源的意义。
