title: Phylogeography sheds light on the central-marginal hypothesis in a Mediterranean narrow endemic plant.
abstract: OBJECTIVE
  Understanding the factors that shape variation in genetic diversity across the geographic ranges of species is an important challenge in the effort to conserve evolutionary processes sustaining biodiversity. The historical influences leading to a central-marginal organization of genetic diversity have been explored for species whose range is known to have expanded from refugia after glacial events. However, this question has rarely been addressed for Mediterranean endemic plants of azonal habitats such as rocky slopes or screes. In this context, this comprehensive study examined molecular and field data from Arenaria provincialis (Caryophyllaceae), a narrow endemic plant of south-eastern France.
  
  
  METHODS
  Across the whole geographic range, an investigation was made of whether high levels of abundance and genetic diversity (estimated from amplified fragment length polymorphism markers) are centrally distributed, to evaluate the relevance of the central-marginal hypothesis. Phylogeographic patterns inferred from chloroplast DNA (cpDNA) were used, applying Bayesian methods to test the influence of past biogeographic events. Multivariate analysis combining phylogeographic and ecological data was used to reveal the historical and ecological distinctiveness of populations.
  
  
  RESULTS
  Despite the narrow distribution of A. provincialis, a high level of nucleotide variation is found within cpDNA loci, supporting its persistence throughout the Pleistocene period. The area characterized by the highest genetic diversity is centrally located. Structured phylogeography and Bayesian factor analysis supported the hypothesis that the central area of the distribution was the source of both westward and eastward migrations, probably during arid periods of the Pleistocene, and more recently was a crossroads of backward migrations. By contrast, the two areas located today at the range limits are younger, have reduced genetic diversity and are marginal in the ecological gradients.
  
  
  CONCLUSIONS
  This study highlights a case of strong population distinctiveness within a narrow range. Phylogeography sheds light on the historical role of the areas centrally situated in the distribution. The current range size and abundance patterns are not sufficient to predict the organization of genetic diversity.
authors: Aix-Marseille Université, Institut Méditerranéen de Biodiversité et d'Ecologie (IMBE, UMR CNRS 7263), Technopôle de l'Environnement Arbois-Méditerranée, BP 80, 13545 Aix-en-Provence cedex 04, France.
authors: Marine
authors: M
authors: Pouget
authors: Sami
authors: S
authors: Youssef
authors: Jérémy
authors: J
authors: Migliore
authors: Marianick
authors: M
authors: Juin
authors: Frédéric
authors: F
authors: Médail
authors: Alex
authors: A
authors: Baumel
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D031243:Arenaria Plant / Q000235:genetics*; D001483:Base Sequence; D018742:DNA, Chloroplast / Q000235:genetics; D005602:France; D006239:Haplotypes / Q000235:genetics; D019083:Mediterranean Region; D008954:Models, Biological; D010802:Phylogeny; D058974:Phylogeography
chemical_list: D018742:DNA, Chloroplast
keywords: Arenaria provincialis; Caryophyllaceae; Pleistocene; Provence; central–marginal hypothesis; conservation; ecological niche; genetic diversity; geographic range; migration; population distinctiveness
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