Adil GÜNER, Vehbi ESER - optima

CHROMOSOME NUMBER AND GENOME SIZE ASSESSMENT OF
LEBANESE TAXA OF ASTRAGALUS GENUS
Farah ABDEL SAMAD 1 , Georges TOHME 2 , Sonja SILJAK YAKOVLEV 2 , Frédéric
MEDAIL 2 , Magda BOU DAGHER KHARRAT 1 .
1Département Sciences de la Vie et de la Terre, Université Saint Joseph, Campus Sciences et technologies, Mar
Roukos, Mkalles, BP: 1514 Riad el Solh, Beyrouth 1107 2050 Liban
2 Aix-Marseille Université (Université Paul Cézanne), Institut Méditerranéen d’Ecologie et de Paléoécologie
(IMEP, UMR CNRS/IRD 6116), Europôle Méditerranéen de l’Arbois, Bâtiment Villemin BP80, 13545 Aix-en-
Provence Cedex 04, France
The Mediterranean basin is one of the world’s major centers for plant biodiversity, where
10% of the world’s higher plants can be found in an area representing only 1.6% of the
Earth’s surface (Médail F. & P. Quézel, 1997). Within the Mediterranean Basin, Lebanon is a
recognized center of plant diversity and is considered as global biodiversity hotspot (Myers N.
et al., 2000). Its floristic richness includes 2,600 vascular plant species of which ca. 92 are
endemic to Lebanon (3.5%) (Mouterde P., 1966, 1970, 1983).
The genus Astragalus L. constitutes a key component of this plant biodiversity in Lebanon
since it is represented by 59 species of which ca. 47 are endemic (Tohmé G. & H. Tohmé,
2007). Astragalus is not only the largest in number of taxa rather it is also considered as one
of the most diverse and taxonomically difficult genera in legumes.
Therefore, the delimitation of Astragalus at various taxonomic ranks poses considerable
taxonomic problems worldwide. It has been widely established that morphological characters
alone are not sufficient to explain the systematic relationships and evolutionary processes
among Astragalus species.
In order to obtain a better understanding of the phylogenetic relationships among species and
of the karyotype evolutionary mechanisms that have operated in Astragalus genus, we
undertook the assessment of chromosome number, karyotype evolution, genome size and
ploidy level of the Lebanese species of Astragalus with special emphasis on endemic taxa.
To our knowledge, no genome size data is available for Astragalus genus. Values obtained in
our study varied between 1.68 pg/2C for Astragalus angulosus DC. and 10.97 pg/2C for
Astragalus deinacanthus Boiss. For most of the studied taxa, the chromosome number seems
to be stable with 2n = 2x = 16 chromosomes.
Keywords: Astragalus L., Chromosome Number, Genome Size, Endemism, Lebanon
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