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Genetic distinctiveness but low diversity characterizes rear-edge Thuja standishii (Gordon) Carr. (Cupressaceae) populations in southwest Japan

Worth, JRP, Tamaki, I, Tsuyama, I, Harrison, PA ORCID: 0000-0002-3502-0242, Sugai, K, Sakio, H, Aizawa, M and Kikuchi, S 2021 , 'Genetic distinctiveness but low diversity characterizes rear-edge Thuja standishii (Gordon) Carr. (Cupressaceae) populations in southwest Japan' , Diversity, vol. 13, no. 5 , pp. 1-24 , doi:

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Rear-edge populations are of significant scientific interest because they can contain allelic variation not found in core-range populations. However, such populations can differ in their level of genetic diversity and divergence reflecting variation in life-history traits, demographic histories and human impacts. Using 13 EST-microsatellites, we investigated the genetic diversity and differentiation of rear-edge populations of the Japanese endemic conifer Thuja standishii (Gordon) Carr. in southwest Japan from the core-range in northeast Japan. Range-wide genetic differentiation was moderate (Fst = 0.087), with northeast populations weakly differentiated (Fst = 0.047), but harboring high genetic diversity (average population-level Ar = 4.76 and Ho = 0.59). In contrast, rear-edge populations were genetically diverged (Fst = 0.168), but contained few unique alleles with lower genetic diversity (Ar = 3.73, Ho = 0.49). The divergence between rear-edge populations exceeding levels observed in the core-range and results from ABC analysis and species distribution modelling suggest that these populations are most likely relicts of the Last Glacial Maximum. However, despite long term persistence, low effective population size, low migration between populations and genetic drift have worked to promote the genetic differentiation of southwest Japan populations of T. standishii without the accumulation of unique alleles.

Item Type: Article
Authors/Creators:Worth, JRP and Tamaki, I and Tsuyama, I and Harrison, PA and Sugai, K and Sakio, H and Aizawa, M and Kikuchi, S
Keywords: approximate Bayesian computation; central-marginal hypothesis; gene-flow; genetic drift; Japanese endemic conifer; leading edge; relictual population
Journal or Publication Title: Diversity
Publisher: MDPIAG
ISSN: 1424-2818
DOI / ID Number:
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Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons 4.0 International (CC BY 4.0) license (

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