Phytogeography of Genu and Homag, two mountains with an Irano-Turanian flora in the Saharo-Sindian regional zone, south Iran

The Saharo-Sindian regional zone encompasses the flat and arid areas of North Africa, the Arabian Peninsula, southern Iran and the deserts of Pakistan and west India. There are some scattered mountains situated within this area, like Hoggar in Sahara, Saint Catherine in Sinai and Genu and Homag in southern Iran. These highlands serve as interglacial refugia for cold adapted plant species. In the present study, phytogeographical patterns and relationships of the flora of Genu and Homag mountains are described and discussed in relation to the phytogeography of the flora of low-lying Hormoz Island. According to a chorological assesment of the flora, Genu and Homag mountains belong to the Irano-Turanian region with 59% of the species restricted to this area. In contrast, the surrounding lowland plains are part of the Saharo-Sindian area with a rather high proportion of widespread species (17%) and Somalia-Masai-linking elements (20%). It is noteworthy that several Turanian enclaves also occur in the lowland zone. Furthermore, the distributional patterns imply that the mountainous Irano-Turkestanian region is an integrated area which is supposedly distinct from the Turanian lowland areas in the north and from the Saharo-Sindian lowland areas in the south. On the other hand, the expansive floras of Turanian and Saharo-Sindian regions are linked to each other. Endemic species in lowland areas in south Iran are mostly either frost sensitive vicariants of cold adapted Turanian species or of Saharo-Sindian origin, while the highland endemics in the area trace their origins to the Irano-Turkestanian region.