Chloroplast DNA polymorphisms in eastern hemlock: range-wide genogeographic analyses and implications for gene conservation
Abstract:The objective of this study was to determine if the genetic diversity of eastern hemlock (Tsuga canadensis (L.) Carrière) is uniformly distributed or structured. Such information is relevant to help guide conservation efforts. Individuals were sampled in 60 range-wide populations of T. canadensis and genotyped at seven polymorphic chloroplast DNA loci. All 16 chlorotypes identified in T. canadensis were highly divergent from the unique chlorotype detected in Carolina hemlock (Tsuga caroliniana Engelm.). Among-population differentiation in T. canadensis was low (G ST = 0.020) and the distribution of chlorotypes did not show any strong geographical pattern, which is likely due to the homogenizing effect of pollen gene flow during the Holocene. Nevertheless, a spatial Bayesian approach revealed two distinct groups of populations. Furthermore, an analysis of relative genetic distances indicated that southeastern Appalachian populations harboured greater population differentiation while conserving relatively high allelic richness, which might represent the imprint of an ancient glacial refugium in the region. Thus, these distinctive genetic patterns and the risk of Tsuga decline following climate warming combined with the introduction of the insect Adelges tsugae (Annand) indicate that the southern part of the range should be considered of high priority for ex situ conservation.
Document Type: Research Article
Affiliations: 1: Chaire de recherche du Canada en génomique forestière et environnementale, Centre d’étude de la forêt et Institut de biologie intégrative et des systèmes, 1030 avenue de la Médecine, Université Laval, Québec, QC G1V 0A6, Canada. 2: Natural Resources Canada, Canadian Forest Service, Canadian Wood Fibre Centre, 1055 du P.E.P.S., P.O. Box 10380, Stn. Sainte-Foy, Québec, QC G1V 47C, Canada. 3: Chaire de recherche du Canada en génomique forestière et environnementale, Centre d’étude de la forêt et Institut de biologie intégrative et des systèmes, 1030 avenue de la Médecine, Université Laval, Québec, QC G1V 0A6, Canada.
Publication date: May 19, 2011
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