Floristic Diversity of Riparian Plants in Aswan Reservoir at the Extreme South of the River Nile, Upper Egypt: A Closed Ecological System

Abstract

The present study was undertaken to survey the floristic composition in the islands and shorelines in Aswan Reservoir, south of the River Nile at Aswan Governorate, Egypt. Four elements of vegetation were analyzed: floristic composition, lifespan, life form, and phytogeographical affinities. A total of 165 species were recorded belonging to 134 genera in 45 families of vascular plants, of which six species were new to the flora of Aswan and Nubia (Amaranthus spinosus, Doellia bovei, Eleocharis parvula, Haematoxylum campechianum, Polygonum aviculare, and Pithecellobium dulce). The most represented families are Leguminosae, Poaceae, and Compositae. Species richness is highest in low-lying areas (shorelines) liable to flooding, compared to those of the islands in the river. The recorded flora consists of 50.91% perennials and 49.09% annuals. Therophytes and phanerophytes were the predominant life forms. Phytogeographical analysis revealed the prevalence of the pantropical (28.48%), palaeotropical (17.57%), and cosmopolitan (16.36%) plant species. Monoregional chorotype was represented by 29 species (17.58%) of the recorded flora with the Sudano-Zambezian species (11.52%) being the highest chorotype, while pure Mediterranean species were very poorly represented (3.63%). Biregional chorotype was represented by 25 species (15.15%), while the pluriregional chorotype was accounted for 2.43% of recorded species.