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Bayesian inference of evolutionary history from chloroplast microsatellites in the cosmopolitan weed Capsella bursa-pastoris (Brassicaceae)

Authors

  • ALF CEPLITIS,

    1. Department of Conservation Biology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-75236 Uppsala, Sweden
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  • YINGTAO SU,

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    • *

      Present address: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Dag Hammarskjölds väg 181, SE-750 07 Uppsala, Sweden

  • MARTIN LASCOUX

    1. Department of Conservation Biology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-75236 Uppsala, Sweden
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Alf Ceplitis, Present address: Department of Cell and Organism Biology, Lund University, Sölvegatan 29, SE-22362 Lund, Sweden. Fax: +46 46 147874; E-mail: alf.ceplitis@cob.lu.se.

Abstract

Besides showing an extraordinary degree of phenotypic variability, Capsella bursa-pastoris (Brassicaceae) is also one of the world's most common plant species and a serious weed in many countries. We have employed a coalescent-based Bayesian analysis of chloroplast microsatellite data to infer demographic and evolutionary parameters of this species. Two different demographic models applied to data from seven chloroplast microsatellite loci among 59 accessions show that the effective population size of C. bursa-pastoris is very small indicating a rapid expansion of the species, a result that is in accordance with fossil and historical data. Against this background, analysis of flowering time variation among accessions suggests that ecotypic differentiation in flowering time has occurred recently in the species’ history. Finally, our results also indicate that mononucleotide repeat loci in the chloroplast genome can deteriorate in relatively short periods of evolutionary time.

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