Plants of Sabkha Ecosystems of the Arabian Peninsula.

Sabkhas are unique ecosystems that are highly saline and where specially adapted plants are able to grow, flower, and fruit. In general, saline environments are poor in species – for the Arabian Peninsula about 120 taxa are recorded as halophytes which constitute about 4% of the total flora of the Arabian Peninsula. Key halophytes of Arabia are nearly always perennial; predominant life-forms are somewhat succulent, semiwoody dwarf shrubs belonging to the families Amaranthaceae, Zygophyllaceae, and Plumbaginaceae and hemicryptophytes belonging to the Poaceae, Cyperaceae, and Juncaceae; annuals are exceptions. Coastal species are either obligate halophytes or salt-tolerant genera from unspecialized families, such as Sporobolus and Aeluropus (Poaceae), or salt-secreting species such as Avicennia (Acanthaceae) and Limonium (Plumbaginaceae). The submerged coastal vegetation, e.g., seagrasses, is one of the most important vegetation types of the Gulf coast and is of great importance to marine fauna. The north-south distribution of coastal species is more distinct on the Red Sea coast, with the border lying near Jeddah, than on the Persian Gulf coast where there is a broad transitional zone between Qatar and northern Oman. The east-west distribution of coastal species is not as distinct. The eastern elements are either restricted to the coasts around the Arabian Gulf or are Irano-Turanian species extending into the Gulf region. Several vicariant species groups of halophytes are represented in the Arabian Peninsula. Halophytes have developed strategies for seed germination such as high germination levels and fast germination speed. These traits are found in the sabkha plants of the Arabian Peninsula. Some halophytes have been investigated for their potential for phytoremediation in their ability to survive weathered oil-contaminated soils. They have been found to have a set of micoorganisms around their root system that are related to the degradation of oil in contaminated soils. Sabkha ecosystems are being degraded and altered throughout the Gulf countries as they appear to be nonproductive. Over the last two decades, there has been a growing concern in protecting and restoring mangroves, and programs do to so have seen promising results. But, on the whole, coastal and inland sabkhas are neglected, and these unique ecosystems require urgent protection

Molecular phylogenetic and biogeographical analysis of Nitraria based on nuclear and chloroplast DNA sequences

Based upon DNA sequences from six plastid regions (rbcL, psbB-psbH, trnL-trnF, rpS16, psbA-trnH, rpS16-trnK) and the internal transcribed spacer (ITS) region of nuclear ribosomal DNA, the phylogenetic relationships in the genus Nitraria and family Nitrariaceae are investigated by using methods of maximum parsimony, maximum likelihood, and Bayesian inference. Our study strongly supports the monophyly of Nitraria. Nitraria can be divided into four parts, namely, the N. sphaerocarpa group, N. retusa group, the N. roborowskii and N. tangutorum group, and a group consisting of N. schoberi, N. komarovii, N. sibirica, and N. billardieri. Ancestral area reconstruction using S-Diva shows that eastern Central Asia is most likely the place of origin, and then dispersals occurred to western Central Asia, Africa, and Australia