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Accueil du site → Doctorat → Allemagne → 2010 → Phylogeny of Eurasian Stipeae, genetic structure and seed germination of Stipa spp. in Jordan

Martin-Luther-Universität Halle-Wittenberg (2010)

Phylogeny of Eurasian Stipeae, genetic structure and seed germination of Stipa spp. in Jordan

Hamasha, Hassan

Titre : Phylogeny of Eurasian Stipeae, genetic structure and seed germination of Stipa spp. in Jordan

Auteur : Hamasha, Hassan Refai

Université de soutenance : Martin-Luther-Universität Halle-Wittenberg

Grade : Doctor rerum naturalium (Dr. rer. nat) 2010

Résumé partiel
Jordan is of great interest to vegetation ecology as it has a unique topography that varies markedly over very short distances which has led to the formation of several distinct bioclimatic regions. The genetic diversity, population structure and seed germination were studied for four Jordanian Stipa species occurring along a common environmental gradient spanning arid habitats with highly variable and unpredictable rainfall to Mediterranean habitats with less variable and more predictable rainfall. The central objective of the present thesis was to test whether the environmental gradient affects genetic diversity, population structure and seed germination of Jordanian Stipa species in a similar or distinct manner. As hitherto no molecular study of the Old World Stipeae had been conducted, a study into the phylogeny of Eurasian Stipeae species, including the Jordanian Stipa species, was undertaken. In general, genetic diversity correlated positively with population size, whereas both genetic diversity and seed germination percentage correlated negatively with rainfall. Our results showed, however, that the four Jordanian Stipa species respond differently, along the same ecogeographical gradient. In terms of their population genetic characteristics, they can be divided into two major groups. The first group, which is composed of the ruderal species S. capensis and S. parviflora, exhibited higher genetic diversity than the second group of closely related semi-desert species S. arabica and S. lagascae, but genetic differentiation was stronger in the semi-desert species than in the ruderals. The genetic diversity of the ruderals was mostly affected by population size while the genetic diversity of the semi-desert species was more strongly affected by the environmental gradients of temperature and precipitation. Principal coordinate analysis (PCoA) and STRUCTURE analysis showed that the Stipa populations were grouped ecogeographically, because those sharing the same climatic and edaphic environment grouped together in the same cluster irrespective of the geographic distances between them. The Saharan Mediterranean populations of Jordanian Stipa were clearly separated from the semiarid and arid Mediterranean populations in all studied species,

Mots clés  : Jordanien Federgras Genetische Variabilität Online-Publikation Hochschulschrift

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