title: Genetic diversity and differentiation of core vs. peripheral populations of eastern white cedar, Thuja occidentalis (Cupressaceae).
abstract: OBJECTIVE
  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).
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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.
authors.forename: Madhav
authors.initials: M
authors.lastname: Pandey
authors.forename: Om P
authors.initials: OP
authors.lastname: Rajora
mesh_terms: D002170:Canada; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D018895:Microsatellite Repeats / Q000235:genetics; D010802:Phylogeny; D011156:Population Density; D029783:Thuja / Q000235:genetics*