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Haïfa University (2010)

Effect of the natural patchy habitat in the southern Arava valley on the population’s genetic structure of generalist and specialist species

Peled, Elad

Titre : Effect of the natural patchy habitat in the southern Arava valley on the population’s genetic structure of generalist and specialist species

Auteur : Peled, Elad

Etablissement de soutenance : Haïfa University

Grade : Master 2010

Résumé
Biodiversity crisis is a global problem shared by all biomes. The ultimate cause of biodiversity decline is the human growing population which leads to intensive land use and habitat fragmentation and destruction. The Arava valley is an arid region characterized by a natural patchy landscape caused by different soil types and topography that creates patches of different habitats with different characteristics such as sand dunes, alluvial fans, salt flats and areas of stabilized sand. Moreover, in the last few decades human activity leads to increased fragmentation of natural habitats mainly due to use of land for settlements and agriculture. The aim of this study is to characterize the genetic structure of several species that inhabit different habitats in the southern part of the Arava valley, and to check whether this natural patchy landscape has a different impact on the population’s genetic structure and variation of specialists compared with generalists. The preliminary hypothesis is that the natural patchy landscape will have a pronounced impact on gene flow within geographically distant populations and that a larger effect on genetic variation will be found in specialists. Two gecko species of the same genus where sampled, Middle Eastern short-fingered gecko (Stenodactylus doriae), which is restricted to sandy habitat and Lichtenstein’s short-fingered gecko (S. sthenodactylus), that populate various habitats with different soil types. In addition I sampled two rodent species of the same genus, Lesser Egyptian gerbil (Gerbillus gerbillus), a psamophiilic gerbil that inhabit sand dunes and Baluchistan gerbil (G. nanus) that inhabit different soil types. S. doriae and G. gerbillus inhabit the mixed stabled sand and sand dunes area north to Yotvata and the Samar dunes area, while S. sthenodactylus and G. nanus inhabit the edge of the sand dunes, at disturbed areas, stabilized sands near Evrona salt marsh, and vegetated alluvial fans. A total of 156 individuals of both gecko species where trapped and sampled, using drift fences and pitfall traps, and by hand trapping. A total of 87 individuals of both gerbil species where trapped and sampled using Sherman traps in the southern Arava, as well as 71 individuals from Mali and Mauritania, W. Africa. The genetic structure of the species and the populations was examined by the AFLP method. The results indicate that Samar’s S. doriae population exhibit remarkably high Heterozygosity (He=0.42) compared to the two other populations that areto the north and south He=0.285-0.3 and 0.2 accordingly). This high heterozygosity is surprising since the Samar population inhabit a relatively small dune (2.3 square kilometers compared to 80 square kilometers of the northern population). Samar’s population was found to be genetically unique and relatively far from the populations surrounding it. S. sthenodactylus northern population was found to be distinct from one of the populations sampled in the southern tip of Evrona salt marsh. The G. gerbillus population from Samar dunes showed high heterozygosity values, similar to W. Africa populations (He> 0.36 ) and different from the Arava northern population (He = 0.24). An opposite trend was found in G. nanus : a higher heterozygosity values in the Arava populations (He = 0.29-0.34) relative to W. Africa (He = 0.10-0.16). In addition, Samar population was found to be genetically distinct from the two other population in the Arava and showed low heterozygosity values, similarly to W. Africa populations (He = 0.13). The Arava populations of this species found to be genetically distinct from W. Africa populations. The results indicate that there is a partial gene flow between populations of the different species tested. Contrary to the hypothesis that the natural patchy landscape will affect more the genetic structure of specialists, it was found that the patchy landscape creates a structure of relatively isolated populations in two species – S. doriae (a specialist) and G. nanus (a generalist). The study shows that Samar dunes are a unique habitat, inhabiting species with unique characteristics.

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Page publiée le 1er décembre 2018, mise à jour le 17 février 2021