Revised systematics of Mediterranean Arundo (Poaceae) based on AFLP fingerprints and morphology

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Phylogenetic relationships and infrageneric classification of Astragalus tragacantha L. (Fabaceae), inferred from nuclear ribosomal DNA Internal transcribed spacers data (nrDNA ITS)

Astragalus (Fabaceae) is one of the most species rich genera of Angiosperms and is the object of several systematic works. In this study, we produce original molecular data (nrDNA ITS) for Astragalus tragacantha L. (subgenus Cercidothrix Bunge, section Tragacantha DC), a rare thorny cushion-forming shrub, occurring in the West Mediterranean basin. Investigation of Genbanck nucleotidic sequence database allows us to place this species in the phylogenetic context of its genus. Our analyses show that its relatives do not possess similar morphology. In fact, A. tragacantha is clearly separated from most of the thorny cushion-forming astragals as subgenus Tragacantha Bunge. Comparison between A. tragacantha and relatives of its clade emphasizes this diversity with ecological, morphological and biogeographic characters at an infrageneric scale. This result presents necessity to increase the molecular systematics of species with similar morphology and biogeography.Astragalus (Fabaceae) est un genre complexe à forte richesse spécifique, ce qui lui vaut d’être au centre de nombreux travaux systématiques. Cette étude fournit des séquences nucléotidiques inédites (ITS nrADN) d’Astragalus tragacantha L. (sous-genre Cercidothrix Bunge, section Tragacantha DC), une espèce rare en forme de coussinet épineux, présente dans l’ouest du bassin méditerranéen. La consultation des séquences nucléotidiques disponibles sur Genbanck nous a permis de définir la place de cette astragale au sein de la phylogénie moléculaire du genre. Au sein du clade contenant les plus proches parents séquencés d’A. tragacantha, nous observons une forte diversité des caractères morphologiques, écologiques et biogéographiques. De plus, A. tragacantha est nettement séparée du clade contenant la plupart des astragales épineuses déjà séquencées (majoritairement du sous-genre Tragacantha Bunge). Cette étude appuie la pertinence de l’outil moléculaire pour la systématique du genre Astragalus, notamment pour des espèces proches sur le plan de la morphologie et de la biogéographie.Hardion Laurent, Baumel Alex, Dumas Pierre-Jean, Duong Nathalie, Affre Laurence, Tatoni Thierry. Phylogenetic relationships and infrageneric classification of Astragalus tragacantha L. (Fabaceae), inferred from nuclear ribosomal DNA Internal transcribed spacers data (nrDNA ITS). In: Ecologia mediterranea, tome 36 n°1, 2010. pp. 99-106

Origine de l'Astragale de Marseille

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Data from: Avian cephalic vascular anatomy, sites of thermal exchange, and the rete ophthalmicum

The general anatomy of avian cephalic blood vessels is well known and there are published details of their role in physiological thermoregulation. Unfortunately, the finer details of vascular pathways to and from sites of thermal exchange are not well known. Additionally, the role of the rete ophthalmicum (RO), a vascular heat exchanger in the temporal region, has been investigated in terms of brain temperature regulation, yet only the arteries have received substantial attention. Without anatomical details of both the arterial and venous pathways, the role of blood vessels in physiological thermoregulation is incomplete. Cephalic vascular anatomy of multiple avian taxa was investigated using a differential-contrast, dual-vascular injection technique and high-resolution X-ray microcomputed tomography. Sites of thermal exchange (oral, nasal, and orbital regions) and the RO were given special attention due to their known roles in cephalic thermoregulation. Blood vessels to and from sites of thermal exchange were investigated to detect conserved vascular patterns and their ability to deliver cooled blood to the RO and dural venous sinus. Sites of thermal exchange were supplied by arteries directly and through collateral pathways. Veins were found to offer multiple pathways that could influence the temperature of neurosensory tissues, as well as pathways that would bypass neurosensory tissues. These results question the paradigm that arterial blood from the RO is the primary method of brain cooling in birds. A shift in the primary role of the RO from brain cooling to regulating and maintaining the temperature of the avian eye should be further investigated

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

International audienceUnderstanding 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