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Clonal and spatial genetic structures of aspen (Populus tremuloides Michx.)

Authors

  • MARIE-CLAIRE NAMROUD,

    Corresponding author
    1. Chaire AFD, Université du Québec en Abitibi-Témiscamingue, 445 boul. de, l’Université, Rouyn-Noranda, Quebec J9X 5E4, Canada,
    2. Groupe de Recherche en Écologie Forestière Interuniversitaire (GREFI), Université du Québec à Montréal, Biological Sciences Department, C.P. 8888 Succ. Centre-Ville, Montreal, Quebec H3C 3P8, Canada
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  • ANDREW PARK,

    1. Groupe de Recherche en Écologie Forestière Interuniversitaire (GREFI), Université du Québec à Montréal, Biological Sciences Department, C.P. 8888 Succ. Centre-Ville, Montreal, Quebec H3C 3P8, Canada
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  • FRANCINE TREMBLAY,

    1. Chaire AFD, Université du Québec en Abitibi-Témiscamingue, 445 boul. de, l’Université, Rouyn-Noranda, Quebec J9X 5E4, Canada,
    2. Groupe de Recherche en Écologie Forestière Interuniversitaire (GREFI), Université du Québec à Montréal, Biological Sciences Department, C.P. 8888 Succ. Centre-Ville, Montreal, Quebec H3C 3P8, Canada
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  • YVES BERGERON

    1. Chaire AFD, Université du Québec en Abitibi-Témiscamingue, 445 boul. de, l’Université, Rouyn-Noranda, Quebec J9X 5E4, Canada,
    2. Groupe de Recherche en Écologie Forestière Interuniversitaire (GREFI), Université du Québec à Montréal, Biological Sciences Department, C.P. 8888 Succ. Centre-Ville, Montreal, Quebec H3C 3P8, Canada
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Marie-Claire Namroud, Fax: (819) 797 4727; E-mail: marie-claire.namroud@uqat.ca

Abstract

To portray aspen clonal and spatial genetic structures, we mapped and genotyped trees in two 1-ha plots, each containing three aspen cohorts originating from fire or subsequent secondary disturbances. We used four microsatellite loci to identify aspen clones and increment core analysis to determine tree age. Clonal dimensions were measured by the maximum distance between two ramets and the number of ramets per genet. Standard normal deviate (SND) was used to assess the spatial distribution of aspen genets and cohorts, and multivariate spatial genetic autocorrelations to assess the spatial distribution of aspen genetic variation. Most aspen genets consisted of only one ramet (> 75%). Median clonal dimensions were 19 and 29 m (maxima: 104 and 72 m in the two plots). No segregation was observed between clones. Aspen cohorts were spatially segregated but trees were spatially aggregated within old and medium-aged cohorts. In contrast, trees were more randomly distributed within the youngest cohorts. This coincided with a spatial genetic autocorrelation at small scales (up to 30 m) in the older cohorts and a more random genetic distribution in the youngest ones. Our results suggest that aspen spatial genetic structuring reflects the spatial patterns produced by the regeneration of discrete cohorts at different stages of succession. Vegetative reproduction leads to aspen genetic spatial structuring at small scales (few metres) until midsuccession. However, as the stand gets older, the spatial distribution of aspen trees and genetic structure evolve from a structured pattern to a more random one under a gap disturbances regime.

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