Southwestern Arabian Peninsula Research Articles

Humid phases on the southwestern Arabian Peninsula are consistent with the last two interglacials

Past environmental and climatic conditions within the Arabian Peninsula are key to understanding the setting for hominin dispersal across the Saharo-Arabian dryland belt. The tufa deposits within the volcanic harrats on the southwest coast of Saudi Arabia fill a significant spatial gap in the distribution of palaeoenvironmental records on the west coast of the Arabian Peninsula adjacent to the Red Sea. In the catchment of Wadi Dabsa in the Harrat Al Birk, there are widespread fossil palustrine to shallow-lacustrine tufa deposits with fluvial elements. Several phases of tufa accumulation, separated by fluvial downcutting, are observable within these powerful palaeoenvironmental proxies. U–Th dating of targeted dense, banded tufa facies, yield ages that are stratigraphically consistent at the landscape scale, and indicate that tufa accumulation occurred during distinct humid phases broadly coeval with the last two warm interglacial Marine Isotope Stages (MIS 7 and MIS 5). For the first time this shows humid intervals in southwest Arabia coincident with the southern coast. There is a simlar pattern emerging further north in the Arabian Peninsula, The Sinai and Levant and further on into continental Europe. Furthermore, tufa δ18O ranges from −14.6 to −1.9‰, covering a range similar to those reported for tufa from north African oasis sites and speleothems elsewhere on the Arabian Peninsula and The Levant. The lowest δ18O values are derived from MIS 5e samples, a pattern in agreement with speleothems in Yemen and Oman, and consistent with an isotopic-enabled climate model simulation for this time slice. The δ13C and Sr isotopic compositions of dated tufa samples indicate deposition from shallow-circulating meteoric water, with no geothermal influence. This, along with the δ18O values, suggest a freshwater supply that was a potable water source in this landscape. The δ13C signatures at Wadi Dabsa are more negative than for parts of north Africa, suggesting Wadi Dabsa may have experienced comparatively higher biomass, thicker soils and wetter conditions with lower evaporative losses. This new record of tufa deposition during the middle and late Pleistocene, suggests for the first time that the west coast of Arabia experienced a similar history of humid phases over the past 250 ka as southern Arabia and the Nefud in the northern interior. These regional changes in hydroclimatic regime occur at timescales coincident with hominin dispersals.

Exploring the association between khat use and psychiatric symptoms: a systematic review

ObjectivesConsumption of the drug khat is high across East Africa and the South-Western Arabian Peninsula despite evidence for its adverse psychiatric effects. This systematic review aims to explore cross-sectional research...

Decadal shift of the influence of Arctic Oscillation on dust weather frequency in spring over the Middle East during 1974–2019

AbstractDust weather has an impact on human health and climate change in the Middle East. In this study, we examined the influence of the Arctic Oscillation (AO) on spring dust weather frequency over the Middle East at an interannual timescale during 1974–2019. The results show that there was an interdecadal shift of the influence of AO on dust weather frequency in the Middle East, with a correlation coefficient between the AO index and dust weather frequency changing from −0.52 during 1974–1994 period (P1) to 0.49 during 1995–2013 period (P2). During P1, negative correlations between AO index and dust weather frequency were found over the northern Arabian Peninsula, and during P2, positive ones were mostly over the central and southwestern Arabian Peninsula. In the lower and middle troposphere, negative geopotential height anomalies are associated with the negative phase of the AO over South Europe during P1, whereas negative geopotential height anomalies are associated with the positive phase of the AO over Northeast Africa during P2. The negative height anomalies resulted in the occurrence of more low‐pressure systems and, thus, dust weather in the Middle East. It is found that the interdecadal shift of the influence of the AO on dust weather was related to an AO‐related northward displacement of wave train propagation during P2. Specifically, during P1 period, the northern branch of AO‐related wave train dominated over the middle latitudes of the North Atlantic across South Europe to the Arabian Peninsula, which resulted in the negative height anomaly over South Europe in the lower and middle troposphere. However, during P2 period, the AO‐related wave train propagation moved northward, and then, the southern branch of the AO‐related wave train dominated over the low latitudes of the North Atlantic across northern Africa to the Arabian Peninsula, which played an important role in the formation of the negative height anomalies over Northeast Africa.

Representation of Arabian Peninsula summer climate in a regional atmospheric model using spectral nudging

This study assesses the performance of the Weather Research and Forecasting (WRF) model in simulating the Arabian Peninsula summer climate for the period 2001–2016. The European Centre for Medium range Weather Forecast (ECMWF) reanalysis is downscaled using WRF without (CTRL) and with the Spectral Nudging (SPN) method. Our results suggest that the noticeable cold biases in surface temperatures (mean, minimum, and maximum) over the Arabian Peninsula in CTRL are significantly reduced in SPN. The seasonal patterns of surface pressure, cloud cover, lower and upper tropospheric circulation, and mid-tropospheric anticyclone are also simulated more realistically with SPN. The evaluation of mean vertical profiles of dynamical and thermo-dynamical features over the Arabian Peninsula further confirms the enhanced simulations with SPN with respect to CTRL. Though SPN captures better the observed evolution of rainfall compared to that of CTRL, it produces a positive rainfall bias over the Southwestern Arabian Peninsula. Stronger vertical motions associated with the local topography enhance the higher water vapor loading, condenses in the upper layers, and results in excess amount of rainfall in SPN. Furthermore, with SPN, WRF is further able to better simulate the synoptic features of heat waves. Overall, SPN enhances WRF simulation skill of the horizontal structures and vertical profiles of the Arabian Peninsula summer climate by enforcing a better balance between the small and large scale features and associated feedbacks.

Guaianolide Sesquiterpene Lactones from Centaurothamnus maximus.

Centaurothamnus maximus (family Asteraceae), is a leafy shrub indigenous to the southwestern Arabian Peninsula. With a paucity of phytochemical data on this species, we set out to chemically characterize the plant. From the aerial parts, two newly identified guaianolides were isolated: 3β-hydroxy-4α(acetoxy)-4β(hydroxymethyl)-8α-(4-hydroxy methacrylate)-1αH,5αH, 6αH-gual-10(14),11(13)-dien-6,12-olide (1) and 15-descarboxy picrolide A (2). Seven previously reported compounds were also isolated: 3β, 4α, 8α-trihydroxy-4-(hydroxymethyl)-lαH, 5αH, 6βH, 7αH-guai-10(14),11(13)-dien-6,12-olide (3), chlorohyssopifolin B (4), cynaropikrin (5), hydroxyjanerin (6), chlorojanerin (7), isorhamnetin (8), and quercetagetin-3,6-dimethyl ether-4’-O-β-d-pyranoglucoside (9). Chemical structures were elucidated using spectroscopic techniques, including High Resolution Fast Atom Bombardment Mass Spectrometry (HR-FAB-MS), 1D NMR; 1H, 13C NMR, Distortionless Enhancement by Polarization Transfer (DEPT), and 2D NMR (1H-1H COSY, HMQC, HMBC) analyses. In addition, a biosynthetic pathway for compounds 1–9 is proposed. The chemotaxonomic significance of the reported sesquiterpenoids and flavonoids considering reports from other Centaurea species is examined.

Plant communities and their environmental drivers on an arid mountain, Gebel Elba, Egypt

Aims: Gebel Elba is an arid mountain range supporting biological diversity that is incomparable to any other region of Egypt. This mountain has a vegetation structure and floristic community similar to the highlands of East Africa and the southwestern Arabian Peninsula. We aimed to provide the first classification of the vegetation units on Gebel Elba and identify the environmental factors controlling their distribution. Study area: Wadi Yahmib and its tributaries, which drain the north-western slopes of Gebel Elba, south-eastern Egypt. Methods: On the basis of 169 relevés, we used TWINSPAN to classify the perennial vegetation. We calculated separate GAMs for the deciduous and evergreen species to describe the patterns for each leaf strategy type with elevation. We used CCA to quantify the relationship between the perennial vegetation and the studied environmental factors. To estimate diversity and our sampling strategy, we used rarefaction curves for species richness. Results: We identified seven communities along the elevational gradient of Wadi Yahmib and its tributaries. We found that each community was restricted to a confined habitat depending on its drought resistance ability. Deciduous Vachellia woodland was the main vegetation type on Gebel Elba, while evergreen Olea woodland appeared in small fragments at higher elevations. We analysed the distribution patterns of deciduous and evergreen trees along the elevational gradient. We found a turnover at 500 m, indicating a potential ecotone between the Vachellia and Olea woodlands that was occupied by a Ficus community. CCA revealed the importance of altitude and soil quality in determining the vegetation structure of Gebel Elba. The species richness increased with elevation as a result of reduced stress and increased water availability at the upper wadis. Conclusions: This study identified seven vegetation units in the study area and showed the importance of orographic precipitation, soil quality and the complex topography in determining the habitats. Taxonomic reference: Boulos (2009); names updated according to POWO (2019). Abbreviations: CCA = Canonical Correspondence Analysis; GAM = Generalized Additive Model; TWINSPANTWINSPAN = Two Way Indicator Species Analysis.

The provenance of obsidian artefacts from the Middle Kingdom harbour of Mersa/Wadi Gawasis, Egypt, and its implications for Red Sea trade routes in the 2nd millennium BC

This paper presents the results of the geochemical analysis carried out on the obsidian artefacts discovered at the archaeological site of Mersa/Wadi Gawasis, located along the Egyptian Red Sea coast, in between the modern cities of Safaja and Quseir. During the 12th and 13th Dynasties of Egypt the site hosted a port city from where the Egyptian expeditions set sail directed to the south, on both edges of the Red Sea. Six obsidian artefacts collected during the 1970s’ research carried out at the site by A. Sayed, were geochemically analysed, together with five geological samples from the obsidian Kusrale source in Eritrea. The major element concentrations were determined by SEM-EDS analysis and the trace element concentrations were obtained by LA-ICP-MS method, a micro-destructive technique, capable of chemically characterizing the volcanic glass. A comparison of geochemical results obtained on the archaeological artefacts and geologic samples, together with the literature data on different geological obsidian outcrops from the Horn of Africa and the southwestern Arabian peninsula, allowed us to determine the provenance of the Mersa/Wadi Gawasis obsidian artefacts in both the Kusrale source of Eritrea, and the volcanic area of Dhamar Reda in Yemen. These results can provide further insights on ancient trade routes along the Red Sea during the early second millennium BC.

The first proven oxychilid land snail endemic to China (Eupulmonata, Gastrodontoidea).

A new and the first proven oxychilid species endemic to China is reported from Sichuan Province. Sinoxychilusgen. nov. is established based on this new species and has diagnostic traits of the sculptured protoconch, partial epiphallus wrapped by developed penis sheath, penial retractor muscle inserting on the top of penial caecum, spinelets on penial pilasters, absence of epiphallic papilla and perivaginal gland present on vagina and proximal bursa copulatrix duct. In light of shell morphology and through geometric morphometric analyses, Zonites scrobiculatus scrobiculatus Gredler and Z. scrobiculatus hupeina Gredler are proposed to be included in the new genus. A phylogenetic inference based on ITS2 gene indicates that the new genus is systematically close to Oxychilus Fitzinger, which is known from the Western Palearctic and the Southwestern Arabian Peninsula, regions that are geographically far from the distribution range of the new genus.

The role of the Indian Summer Monsoon variability on Arabian Peninsula summer climate

This study investigates the influence of the Indian Summer Monsoon (ISM) on the atmospheric circulation over the Arabian Peninsula (AP) using the European Centre for Medium Range Weather Forecasts’ twentieth century reanalysis (ERA-20C) for the period 1901–2010. After describing the summer climate of the AP using various dynamic and thermodynamic parameters, we investigate the link between extreme ISMs and atmospheric circulation over the AP on inter-annual time scale. Analysis of composites of different parameters during extreme monsoon (strong and weak) years reveals that the ISM plays an important role in the summer circulation over the AP and adjoining regions. The major noticeable changes in modulating circulation during extreme monsoons are: (1) a strengthening of lower tropospheric northerly winds, westerly winds passing through the Tokar Gap, Shamal winds, and the upper tropospheric easterly jet stream during strong ISM; (2) a northward (southward) shift of the subtropical westerly jet stream during strong (weak) monsoon years; (3) the development of strong upper level ridge above the surface thermal low during strong ISM years, which result in a baroclinic structure over the AP and adjoining regions; (4) an increase in adiabatic warming, and hence aridity, over the AP during strong monsoon years, caused by intense subsidence of the middle to upper troposphere due to zonal overturning circulation; and (5) convective instability during strong monsoon years caused by an intensification of the upward motion over the southern AP. Furthermore, during strong monsoons, the availability of excess moisture leads to atmospheric instability, which in turn triggers the formation of clouds that lead to more rainfall over the southwestern AP. Finally, the westward propagation of a Gill-type Rossby waves induced by the ISM play an important role in the variations of the AP summer climate by enhancing the warm core structure over the AP and through their interaction with the midlatitude westerlies during strong monsoons.

ENSO relationship to summer rainfall variability and its potential predictability over Arabian Peninsula region

The El Niño Southern Oscillation (ENSO) phenomenon is considered to be responsible for rainfall predictability in many regions. Some of its regional teleconnections, such as over the Arabian Peninsula in boreal summer (June–August) season, are not well studied. Therefore, in this paper, the relationship between the summer seasonal mean rainfall and ENSO is analyzed with the aid of a 15-member ensemble of simulations using the Saudi-King Abdulaziz University (KAU) Atmospheric Global Climate Model (AGCM) for the period 1981–2015. The southwestern peninsula rainfall is linked to the Sea Surface Temperature (SST) anomalies in the central-eastern pacific region. This relationship is established through an atmospheric teleconnection which shows upper-level convergence anomalies over the southern Arabian Peninsula compensating the central-eastern Pacific upper-level divergence anomalies for the warm ENSO phase, and vice-versa for the cold Phase. The upper-level convergence over the southern Arabian Peninsula leads to sinking motion, low-level divergence and consequently to reduced rainfall in the warm phase, while reverse happens in the cold phase. The correlation coefficient between the observed area-averged Niño3.4 index and a Southwestern Arabian Peninsula Rainfall Index (SARI) is −0.43 (statistically significant at 95%). Overall, model shows a potential predictability (PP) of 0.53 for the SARI region. Predictability during El Niño is higher than during La Niña events. This is not only because of a stronger signal, but also noise reduction contributes to the increase of PP in El Niño compared to that of La Niña years.

Sensitivity of AGCM‐simulated regional JJAS precipitation to different convective parameterization schemes

ABSTRACTThis study examines the effects of convective parameterization schemes (CPSs) on the simulated June–September (JJAS) precipitation climatology, variability and predictability over southwestern Arabian Peninsula and northeast Africa during 1981–2014 within an atmospheric global climate model framework. The three CPSs used are: the simplified Arakawa–Schubert (SAS) scheme; the SAS scheme with Tokioka modification (STOK) and the Emanuel (EMAN) scheme coupled with a probability distribution function‐based cloud parameterization scheme. SAS and STOK overestimate JJAS total precipitation over the selected domain compared to observations, while EMAN underestimates. EMAN provides the most realistic distribution of precipitation and spatial distribution of convective precipitation despite the tendency for underestimating the total precipitation. The principal patterns of precipitation variability (as measured by the leading empirical orthogonal functions) in EMAN and STOK are clearly related to the observed pattern, while the maximum variability in SAS occurs in a completely different location. The El Niño Southern Oscillation‐related JJAS precipitation teleconnection simulated by the SAS scheme is very weak as compared to observations and other two CPSs. The signal‐to‐noise ratio estimated by SAS and STOK is very low as compared to EMAN. Correlation analysis shows that EMAN performs better than the other two CPSs. Low (high) outgoing longwave radiation (OLR) values are indicative of enhanced (suppressed) convection and hence more (less) cloud coverage. The root mean square error estimated for OLR in EMAN is lower than that of the other two CPSs. The vertical structure of specific humidity and temperature shows less error in EMAN than that of the other two CPSs, which could be a reason for better predictability over the region of interest.

Disentangling the Pelomedusa complex using type specimens and historical DNA (Testudines: Pelomedusidae).

Recent research has shown that the helmeted terrapin (Pelomedusa subrufa), a species that occurs throughout sub-Saharan Africa, in Madagascar and the southwestern Arabian Peninsula, consists of several deeply divergent genetic lineages. Here we examine all nominal taxa currently synonymized with Pelomedusa subrufa (Bonnaterre, 1789) and provide mitochondrial DNA sequences of type specimens or topotypic material for most taxa. Lectotypes are designated for Testudo galeata Schoepff, 1792, Pentonyx capensis Duméril & Bibron, 1835, Pelomedusa nigra Gray, 1863, Pelomedusa galeata var. disjuncta Vaillant & Grandidier, 1910, and Pelomedusa galeata damarensis Hewitt, 1935. For Pelomedusa gasconi Rochebrune, 1884, a taxon without preserved type material, a neotype is designated. Type material of Pentonix americana Cornalia, 1849, a nominal species without credible type locality, is lost and its identity remains questionable. Also the holotype of Pelomedusa galeata orangensis Hewitt, 1935 is lost, but its allocation to the only genetic lineage occurring in South Africa is unambiguous. Phylogenetic analyses of type sequences or topotypic material reveal that the remaining nominal taxa represent three of the nine previously identified lineages of Pelomedusa. Among these three lineages is the South African one. Type specimens of Pentonyx gehafie Rüppell, 1835 correspond to an additional distinct lineage. The present study provides a sound basis for a subsequent integrative taxonomic revision of the Pelomedusa complex.

Monitors cross the Red Sea: The biogeographic history of Varanus yemenensis

The Red Sea has had a profound biogeographic effect on organisms with Afro-Asian distributions, resulting in complex patterns of admixture on the Arabian Peninsula. We investigate the phylogenetic affinities of a monitor lizard (Varanus yemenensis) restricted to the southwestern Arabian Peninsula by sequencing all African monitor species and several Asian monitor species for the mitochondrial gene ND2 and the nuclear marker RAG-1. We find evidence that V. yemenensis is of African origin, being most closely related to the white-throat monitor, V. albigularis, an African species complex distributed from the Horn of Africa to southern Africa. Using divergence-dating analyses, we investigate several biogeographic hypotheses to infer the likely mechanism of colonization of the Arabian Peninsula by this species. Our results reveal that both dispersal across a southern land bridge and overwater dispersal are potential explanations. The patterns observed in V. yemenensis are contrasted with other taxa having similar Afro-Arabian disjunct distributions to better understand the complex biogeographic history of this region.

Phylogeography of the Middle Eastern tree frogs ( Hyla, Hylidae, Amphibia) as inferred from nuclear and mitochondrial DNA variation, with a description of a new species

Evolutionary relationships of the tree frogs from the Middle East and the demographic histories of their populations were studied using a combination of mitochondrial and nuclear genes. Hyla savignyi and neighboring populations of H. orientalis (former eastern populations of H. arborea) were the main focus taxa. Within H. savignyi, a deep phylogenetic divergence dated about 8.4 Ma was discovered. Southern populations from Yemen, Jordan, southern Syria and extreme north-eastern Israel are hereby described as a new species, H. felixarabica sp. nov. Our study points to a biogeographic connection of the south-western Arabian Peninsula and southern Levant and to the importance of the Dead Sea Rift as a historical barrier geographically separating the new species from H. savignyi. Major genetic breaks revealed within species ( H. felixarabica: Yemen vs. Jordan–Syria; H. savignyi sensu stricto: Levant vs. Turkey–Iran) are probably connected to climate changes during the Plio–Pleistocene boundary, while the finer phylogeographic structuring probably resulted from the Quaternary climate oscillations. The Cypriote population of H. savignyi originated from southern Anatolia relatively recently. Hyla orientalis from the southern Black Sea region seems to be genetically quite uniform, although two phylogeographic units with western Turkish and Caucasus–Caspian affinities might be detected. Hyla savignyi and H. orientalis carry signals of population expansions dated to the middle to late Pleistocene, while populations of H. felixarabica seem to have rather been constant in size, which might indicate more stable climatic conditions in the southern regions during the Quaternary.

Hipposideros caffer (Chiroptera: Hipposideridae)

Hipposideros caffer (Sundevall, 1846) is a hipposiderid bat commonly called Sundevall's leaf-nosed or roundleaf bat. H. caffer is a medium-sized insectivorous bat with a horseshoe-shaped nose leaf and 2 color phases in adulthood. It is 1 of 67 species in the genus Hipposideros and is found in the southwestern Arabian Peninsula, in most of Africa south of the Sahara (excluding the central forested region), and in Morocco, Zanzibar, and Pemba. H. caffer is a savanna-dwelling species and inhabits a variety of roost types including caves, hollow trees, and abandoned buildings. It often roosts in groups of thousands of individuals, is very common, and is not of special conservation concern.

The Anelastic Attenuation of Surface Waves Beneath Southwestern Arabia and the Southern Red Sea

The seismic attenuation coefficients of surface waves in southwestern Arabian Peninsula and the southern Red Sea were inves- tigated using the station ratio method. Love and Rayleigh waves data recorded by two GSN stations RAYN and ATD are used to compute Love and Rayleigh waves attenuation coefficients (γ L and γ R ), and Love and Rayleigh waves internal friction (Quality factors, Q L and Q R ) in the region between the two GSN seismic stations RAYN and ATD. RAYN lies at the center of Arabia, while ATD is located on the western coast of the southern Red Sea on the Afar depression. γ R is found to vary from a low of 4.03 × 10 -4 km -1 at 27 s and a high of 22.9 × 10 -4 km -1 at 44 s. γ L , on the other hand, varies between a mini- mum of -2.28 × 10 -4 km -1 at 6 s and a maximum of 10.81 × 10 -4 km -1 at 23 s. The average quality factors Q R and Q L for the upper crust are estimated to be 100 and 160, respectively. Surface wave attenuation below the upper crust is extremely high. The high attenua- tion of the crust and upper mantle may be explained in the frame work of the ongoing tectonic process of the Red Sea and the Afar depres- sion. High temperature associated with partial melting beneath the crust can result in increasing the attenuation which is observed at long periods, while at short periods (less than 27 s), the level of attenuation is less. However, the attenuation is remarkably high. The results of this confirm previous indications that the Arabian plate, unlike other stable regions, has unusually higher attenuation characteristics for seismic waves in the crust and upper mantle comparable to many tectonically active regions of the world.

Dispersion of the Afar plume: Implications from the Spatiotemporal Distribution of the Late Miocene to Recent Volcanics, Southwestern Arabian Peninsula

Forty-three new K-Ar dates from the Yemen inland volcanic fields (Amran-Sana'a, Dhamar-Rada, and Marib-Sirwah field) in the southwestern Arabian Peninsula reveal a progression that can be divided into four stages: Stage 1: 6.4-5.2 Ma, Stage 2: 3.6-2.9 Ma, Stage 3: 2.2-1.7 Ma and Stage 4: <1.3 Ma. It is clear from the data that the volcanic activity shifted northeastward, overlapping partly during Quaternary time. A similar shift has been recognized along the Aden Volcanic Line from Perim Island to the Aden volcanic field (10-5 Ma) [Mallick et al., 1990]. This study shows that the northeastward or eastward shift for the late Miocene to recent volcanic activity on southwestern Arabian Peninsula is about 3-5 cm/year (average: 4.1 cm/year). The rate of shift may reflect the rate of dispersion of an Afar plume head which impinged at 15 Ma on the base of the Arabian plate. We refine and further develop the Afar plume dispersion model proposed by Schilling et al. [1992]; we consider that two Afar plumes impinged on Afar province at 38 Ma and 15 Ma and that they are continuing to disperse under the Arabian lithosphere. The refined dispersion model we propose is consistent with the known geochemical and mantle tomographical features in the Afar-Arabian province and with the spatiotemporal distribution of late Miocene to recent volcanics in the southwestern Arabian Peninsula.

Notes on the Types of Some Names of Arabian Acanthaceae in the Forsskal Herbarium

Ruellia pallida Vahl is reduced to synonymy of R. patula Jacq. but R. strepens var. caerulea Forssk. is not positively identifiable; a lectotype is chosen for Barleria bispinosa (Forssk.) Vahl, the name of a species confined to the south-western Arabian peninsula; Barleria diacantha Hochst. ex Nees and B. marghilomaniae Volkens & Schweinf. are reduced to synonymy of B. trispinosa (Forssk.) Vahl, the area of which is now extended from Arabia to N.E. tropical Africa; Barleria lanceata (Forssk.) C. Chr. is found to be taxonomically distinct from B. noctiflora L.f., but B. triacantha Hochst. ex Nees is found to be a synonym of it; Barleria appressa (Forssk.) Deflers is considered to be one of eight newly designated subspecies of B. prionitis L., a species now extending through tropical Asia, Arabia and tropical Africa; Justicia sulcata (Vahl) Vahl andJ. suaveolens (Nees) Lindau are reduced to synonymy ofJ.flava (Vahl) Vahl; two variants are noted in Monechma debile (Forssk.) Nees in Arabia and N.E. tropical Africa; a lectotype not in the Forsskal herbarium is chosen for Ecbolium viride (Forssk.) Alston, and the relationship of the African and Arabian material of this species to that from Asia is discussed; the new combination Ecbolium violaceum (Forssk.) Hillcoat & J. R. I. Wood is made, and E. anisacanthus Schweinf. becomes a synonym of this; the new combination Isoglossa punctata (Vahl) Brummitt & J R. I. Wood is published and I. oerstediana Lindau becomes a synonym of it; Dicliptera verticillata (Forssk.) C. Chr. is found to be distinct from D. chinensis L., and a lectotype is chosen for D. micranthes which is a synonym of the former; the new combination Peristrophe paniculata (Forssk.) Brummitt is published, and P. bicalyculata (Retz.) Nees is a synonym of this; Dicliptera zeylanica Nees is reduced to synonymy of D. foetida (Forssk.) Blatter; the name Hypoestesforskalei (Vahl) Solander ex Roem. & Schult. is considered to be correct for the species long known as H. verticillaris, and H. fastuosa (L.) Solander ex Roem. & Schult. is a mystery plant of unknown origin.

Weeds of Southwestern Arabian Peninsula

Abstract A list of weeds and their maximum intensity of infestation observed in agricultural areas in the southwestern Arabian Peninsula is presented.