Geographical isolation caused the diversification of the Mediterranean thorny cushion-like Astragalus L. sect. Tragacantha DC. (Fabaceae)

Laurent Hardion (1, 2) , Pierre-Jean Dumas (1) , Farah Abdel-Samad (1, 3) , Magda Bou Dagher Kharrat (3) , Bostjan Surina (4) , Laurence Affre (1) , Frédéric Médail (1) , Gianluigi Bacchetta (5) , Alex Baumel (1)

1 IMBE - Institut méditerranéen de biodiversité et d'écologie marine et continentale
2 LIVE - Laboratoire Image, Ville, Environnement
3 USJ - Université Saint-Joseph de Beyrouth
4 University of Primorska
5 UniCa - Università degli Studi di Cagliari = University of Cagliari

Understanding the origin and evolution of Mediterranean vascular flora within the long-term context of climate change requires a continuous study of historical biogeography supported by molecular phylogenetic approaches. Here we provide new insights into the fascinating but often overlooked diversification of Mediterranean xerophytic plants. Growing in some of the most stressing Mediterranean environments, i.e. coastal and mountainous opened habitats, the circum-Mediterranean Astragalus L. sect. Tragacantha DC. (Fabaceae) gathers several thorny cushion-like taxa. These have been the subjects of recent taxonomical studies, but they have not yet been investigated within a comprehensive molecular framework. Bayesian phylogenetics applied to rDNA ITS sequences reveal that the diversification of A. sect. Tragacantha has roots dating back to the Pliocene, and the same data also indicate an eastern-western split giving rise to the five main lineages that exist today. In addition, AFLP fingerprinting supports an old east-west pattern of vicariance that completely rules out the possibility of a recent eastern origin for western taxa. The observed network of genetic relationships implies that contrary to what is widely claimed in the taxonomic literature, it is range fragmentation, as opposed to a coastal-to-mountain ecological shift, that is likely the main driver of diversification. (C) 2016 Elsevier Inc. All rights reserved.

Mots clés: Phylogeography; Biogeography; Plant; Biodiversity; Speciation; Vicariance

Domaines: Evolution [q-bio.PE]; Botanique

Laurent Hardion, Pierre-Jean Dumas, Farah Abdel-Samad, Magda Bou Dagher Kharrat, Bostjan Surina, et al.. Geographical isolation caused the diversification of the Mediterranean thorny cushion-like Astragalus L. sect. Tragacantha DC. (Fabaceae). Molecular Phylogenetics and Evolution, 2016, 97, pp.187--195. ⟨10.1016/j.ympev.2016.01.006⟩. ⟨hal-01444679⟩