Disjunct distribution of Hypericum nummularium L. (Hypericaceae): molecular data suggest bidirectional colonization from a single refugium rather than survival in distinct refugia

• Published in: Biological Journal of the Linnean Society
• Main Author: Gaudeul, M.
• Other Authors: Laboratoire d'Ecologie Alpine (LECA), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2006
• Subjects: amplified fragment length polymorphism (AFLP); biogeography; disjunction; dispersal; genetic structure; glaciation; internal; transcribed spacers (ITS); phylogeography; Length polymorphism markers; nuclear ribosomal dna; ice ages; european; alps; alpine plant; saxifraga-oppositifolia; sequence variation; genetic diversity; late quaternary; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDV.BID]Life Sciences [q-bio]/Biodiversity; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; Saxifraga oppositifolia
• Online Access: https://hal.archives-ouvertes.fr/halsde-00293859; https://doi.org/10.1111/j.1095-8312.2006.00583.x

International audience Hypericum nummularium has a strongly disjunct, bi-areal distribution in Europe: it is abundant in the Pyrenees and grows in a very restricted part of the Alps, more than 1000 km away. My aim was to estimate the genetic divergence between these areas and to identify the factors responsible for the disjunction: glacial relicts, bidirectional colonization from a common refugium, long-distance dispersal and/or human introduction? Internal transcribed spacers (ITS) sequencing (680 bp) and amplified fragment length polymorphism (AFLP) fingerprinting (104 polymorphic markers) showed very low differentiation between populations in the Alps and the Pyrenees, indicating that H. nummularium probably survived in a single refugium. Moreover, levels of genetic diversity were similar in the two areas, making human introduction and long-distance dispersal unlikely. Thus, the species probably survived in one refugium, subsequently colonizing both areas more or less simultaneously. The comparison of genetic and geographical distances suggested a step by step migration in the Alps (isolation by distance), whereas random dispersal events were more likely in the Pyrenees. Finally, I discuss possible causes for the restricted distribution area of H. nummularium in the Alps (e.g. unsuitable habitat, low dispersal capacities) and conclude that strong human disturbance is probably the major limit to the expansion of the species in this region. (c) 2006 The Linnean Society of London.