Jacob Thomas

Global exchange and accumulation of non-native plants

All around the globe, humans have greatly altered the abiotic and biotic environment with ever-increasing speed. One defining feature of the Anthropocene epoch is the erosion of biogeographical barriers by human-mediated dispersal of species into new regions, where they can naturalize and cause ecological, economic and social damage. So far, no comprehensive analysis of the global accumulation and exchange of alien plant species between continents has been performed, primarily because of a lack of data. Here we bridge this knowledge gap by using a unique global database on the occurrences of naturalized alien plant species in 481 mainland and 362 island regions. In total, 13,168 plant species, corresponding to 3.9% of the extant global vascular flora, or approximately the size of the native European flora, have become naturalized somewhere on the globe as a result of human activity. North America has accumulated the largest number of naturalized species, whereas the Pacific Islands show the fastest increase in species numbers with respect to their land area. Continents in the Northern Hemisphere have been the major donors of naturalized alien species to all other continents. Our results quantify for the first time the extent of plant naturalizations worldwide, and illustrate the urgent need for globally integrated efforts to control, manage and understand the spread of alien species.

Effectiveness of cuticular transpiration barriers in a desert plant at controlling water loss at high temperatures

Maintaining the integrity of the cuticular transpiration barrier even at elevated temperatures is of vital importance especially for hot-desert plants. Currently, the temperature dependence of the leaf cuticular water permeability and its relationship with the chemistry of the cuticles are not known for a single desert plant. This study investigates whether (i) the cuticular permeability of a desert plant is lower than that of species from non-desert habitats, (ii) the temperature-dependent increase of permeability is less pronounced than in those species and (iii) whether the susceptibility of the cuticular permeability barrier to high temperatures is related to the amounts or properties of the cutin or the cuticular waxes. We test these questions with Rhazya stricta using the minimum leaf water vapour conductance (gmin) as a proxy for cuticular water permeability. gmin of R. stricta (5.41 × 10−5 m s−1 at 25 °C) is in the upper range of all existing data for woody species from various non-desert habitats. At the same time, in R. stricta, the effect of temperature (15–50 °C) on gmin (2.4-fold) is lower than in all other species (up to 12-fold). Rhazya stricta is also special since the temperature dependence of gmin does not become steeper above a certain transition temperature. For identifying the chemical and physical foundation of this phenomenon, the amounts and the compositions of cuticular waxes and cutin were determined. The leaf cuticular wax (251.4 μg cm−2) is mainly composed of pentacyclic triterpenoids (85.2% of total wax) while long-chain aliphatics contribute only 3.4%. In comparison with many other species, the triterpenoid-to-cutin ratio of R. stricta (0.63) is high. We propose that the triterpenoids deposited within the cutin matrix restrict the thermal expansion of the polymer and, thus, prevent thermal damage to the highly ordered aliphatic wax barrier even at high temperatures.

An overview of wetlands of Saudi Arabia: Values, threats, and perspectives

The wetlands of Saudi Arabia are located in a water-stressed region that is highly vulnerable to climate and other global changes. Sebkhas, mudflats, mangroves, and wadis are the dominant wetlands in the arid regions of North Africa and the Arabian Peninsula. These unique wetlands are recognized as a sanctuary for biodiversity and for their economic services generated from mineral extraction, agriculture, and grazing. Despite their ecological values and societal services, the long-term permanence of Saudi Arabia’s wetlands faces strong challenges resulting from human activities associated with sustained population growth, habitat degradation, and coastal development. This paper consolidates a literature review of Saudi Arabia’s wetlands from local to global importance, highlights their biodiversity, and identifies threats and evolution of these vulnerable ecosystems in the arid Arabian Peninsula by focusing on the status of key freshwater taxa (Odonata, freshwater fishes, amphibians, and waterbirds) and documenting changes affecting important wetlands.

Phytochemical evaluation of roots of Plumbago zeylanica L. and assessment of its potential as a nephroprotective agent

Search for medicinal plants to treat kidney disorders is an important topic on phytotherapeutical research. Plumbago zeylanica L. is an important medicinal plant with hepatoprotective, anti-inflammatory, anti-diabetic, anti-cancer and anti-hyperlipidemic activities. In the present study, the protective effect of hydroalcoholic extract of P. zeylanica (HAPZ) in cisplatin induced nephrotoxicity was analyzed in Swiss albino mice. Treatment with higher dose (400 mg/kg) of HAPZ significantly reversed the adverse effect of cisplatin on kidney weight, serum urea and creatinine, indicating their renoprotective effect. The antioxidant effect of the drug is evident from its significant effect on Catalase, Glutathione peroxidase and lipid peroxidation activities.

Vegetation, Floristic Diversity, and Size-Classes of Acacia gerrardii in an Arid Wadi Ecosystem

This study focuses on the vegetation ecology, floristic diversity, and dynamics of Acacia gerrardii populations in wadi Huraimla, Central Saudi Arabia. The floristic richness, plant cover, human impact, and demography of A. gerrardii population were monitored in open grazing and managed sites. The applications of TWINSPAN, DCA, and CCA multivariate analysis have produced nine vegetation groups; eight of them were associated with the distribution of A. gerrardii and one group with the surrounding agricultural lands. The plant communities were separated into three major vegetation groups, viz., Acacia gerrardii-Rhazya stricta representing the open grazing sites, Acacia gerrardii-Lycium shawii-Zilla spinosa representing the managed sites, and Cynodon dactylon-Heliotropium bacciferum-Cenchrus ciliaris dominating the agricultural lands. The CCA ordination indicated that the separation of plant species along the first axis was positively affected by EC, K, Na, species richness and human impact, and negatively affected by pH, Mg, and density and age of A. gerrardii populations. Alternatively, the second axis is positively correlated with altitude and Ca content of the soil. Human impact is positively correlated with soil salinity, K and Na contents and negatively correlated with altitude, soil texture, and Mg content. The density of A. gerrardii is positively correlated with pH, Fe, Mn, and Mg contents of the soil, whereas negatively correlated with salinity and K and Na contents, species richness, relative evenness, and human impact. Populations of A. gerrardii demonstrated different size-class distribution patterns with either continuous regeneration inputs or lack of regeneration.

New generic and species records for the flora of Saudi Arabia.

Recent field works in the central and southern regions of Saudi Arabia including agricultural centers have managed to collect four vascular plants new to terrestrial and wetland flora of the country. These new additions include one new genus Malvastrum A. Gray (M. coromandelianum) subsp. capitato-spicatum (O. Kuntze) S.R. Hill, Potamogeton perfoliatus L. (Potamogetonaceae), Euphorbia tirucalli L. (Euphorbiaceae) and Sesuvium portulacastrum (L.) L. (Aizoaceae). Detailed morphological description, distribution and habitat of each of these species are provided along with illustrations and photographs. The report of new additions to the flora of Saudi Arabia indicated that the country needs thorough botanical explorations.

RETRACTED: Vegetation analysis of Wadi Al-Jufair, a hyper-arid region in Najd, Saudi Arabia

THIS ARTICLE HAS BEEN RETRACTED please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and Author. Data processing errors have resulted in misleading conclusions. The scientific community in King Saud University has serious concerns regarding the results and the article will be resubmitted for publication after reprocessing of the data.

Endemics and endangered species in the biodiversity hotspot of the Shada Mountains, Saudi Arabia

Shada Mountains in Saudi Arabia, separated by Maleel Wadi into twin mountains (i.e., Shada Alalah and Shada Asfal), are rich in biodiversity. We investigated the diversity of endemics and endangered species of the mountains based on the data collected from 38 stands falling in 8 elevational zones ranging from 500 to 2215 m a.s.l. Results indicated that 495 plant species falling in 314 genera and 76 families occurred in the Shada Mountains, including 19 endemic species and 43 endangered species, and accounting for 22% of the total flora in Saudi Arabia. Canonical correlation analysis indicated that physiographic features, particularly altitude play an important role in the frequency and abundance of species. Endemics were not evenly distributed in the Shada Mountains and mostly restricted in the elevation zone of 1000–1500 or >1500 m a.s.l. When the altitude reached up to 2000 m a.s.l., the endemics decreased substantially due to the significantly low temperature. The endangered species existed three different distribution patterns: (i) most endangered species distributed in the altitudes of 1000–1800 m a.s.l.; (ii) endangered trees, lianas, and shrubs occupied the altitudes 1000–1300 m a.s.l.; and (iii) endangered subshrubs and herbs inhabited the altitudes 1500–2100 m a.s.l. The results demonstrated that the biodiversity of endangered species in the Shada Mountains is high and undisturbed by invasive species, and protective measures should be taken against human disturbances to the small-scale hotspot.

Molecular fingerprinting of Helicanthus elastica (Desr.) Danser growing on five different hosts by RAPD

Mistletoes are hemiparasitic plants growing on aerial parts of other host trees. Many of the mistletoes are reported to be medicinally important. The hemiparasitic nature of these plants makes their chemical composition dependent on the host on which it grows. They are shown to exhibit morphological dissimilarities also when growing on different hosts. Helicanthus elastica (Desr.) Danser (mango mistletoe) is one such less explored medicinal mistletoe found on almost every mango tree in India. Traditionally, the leaves of this plant are used for checking abortion and for removing stones in the kidney and urinary bladder while significant antioxidant and antimicrobial properties are also attributed to this species of mistletoe. The current study was undertaken to evaluate molecular differences in the genomic DNA of the plant while growing on five different host trees using four random markers employing random amplified polymorphic DNA (RAPD) followed by similarity matrix by Jaccard’s coefficient and distance matrix by hierarchal clustering analysis. Similarity and distance matrix data employing just 4 random markers, separately and the pooled data as well, revealed significant difference in the genomic DNA of H. elastica growing on five different hosts. Pooled data of similarity from all the 4 primers cumulatively showed similarity between 0.256 and 0.311. Distance matrix ranged from of 0.256 to 0.281 on pooling the data from all the four primers. The result employing a minimum number of primers could conclude that genomic DNA of H. elastica differs depending upon the host on which it grows, hence the host must be considered while studying or utilizing this mistletoe for medicinal purposes.

Development of quality standards of medicinal mistletoe – Helicanthes elastica (Desr.) Danser employing Pharmacopoeial procedures

Helicanthes elastica (Desr.) Danser (Loranthaceae), commonly known as Indian mango mistletoe, is a parasitic shrub found widely growing on mango trees in southern India. Development of monographic quality standards is need of the hour for Pharmacopoeial/extra-Pharmacopoeial and folk medicinal plants. Systematic pharmacognostical evaluation of leaves of H. elastica has been carried out employing Pharmacopoeial procedures of testing herbal drugs. Macro–microscopic features of H. elastica leaf were recorded. Ethanolic extract was tested positive for alkaloids, steroids, carbohydrates, tannins, saponins and phenols. HPTLC fingerprint profile was developed for the identification of extracts using reference standard β-sitosterol glucoside. Results of the present investigation would serve as a source of pharmacognostical information and a document to control the quality of H. elastica (Desr.) Danser.