Hajar Mountains Research Articles

Occurrences and genesis of palygorskite/sepiolite and associated minerals in the Barzaman formation, United Arab Emirates

AbstractThe Barzaman Formation exposed in the United Arab Emirates was deposited as a series of fluvial sediment sequences lying along the western margin of the Hajar Mountains, part of the Oman–UAE ophiolite. This formation consists of a sequence of rocks dominated by variably cemented and altered conglomerates comprising calcareous siltstones and calcareous clays deposited during the Miocene to Pliocene under a humid climate. The conglomerates are composed largely of ultramafic and lesser-mafic clasts. The present study was undertaken in order to understand the occurrence and genesis of palygorskite and sepiolite in relation to the environmental changes including evaporitic and sabkha environments.Sediments were collected from two trenches and a drill hole of ∼22 m depth. Samples were analysed by optical petrograpy, X-ray diffraction and scanning electron microscopy. Pedogenesis occurred at the deeper level in well cemented conglomerate which constitutes the hard crust. Post-depositional erosion started in marine phreatic or vadose zones as shown by the neoformation of serpentine from the weathering of olivine as well as of calcite and dolomite. Neoformation of palygorskite, sepiolite, dolomite and halite occurred under evaporitic conditions on calcareous silty clay facies. Relatively hot, vadose and oxidizing environmental conditions affected the calcareous siltstone facies leading to the genesis of dolomite and palygorskite by direct precipitation from solution rich in Ca, Mg, Al, Fe and Si ions.

Darriwilian shallow-marine deposits from the Sultanate of Oman, a poorly known portion of the Arabian margin of Gondwana

AbstractThe Amdeh Formation is a 3.4 km stack of sparsely fossiliferous quartzites and shales which crops out in the Al Hajar mountains near Muscat. Here we describe the uppermost member (Am5) that can be dated biostratigraphically as Darriwilian and which is the outcrop equivalent, and probably the seaward continuation, of the Saih Nihayda Formation in the Ghaba Salt Basin of northern Oman. The outcrops at Wadi Daiqa and Hayl al Quwasim consist of 690 m of quartzitic sandstones, shales and bivalve-rich shell beds. Trace fossils referable to theCruzianaandSkolithosichnofacies abound. The member comprises storm-dominated shelf, shoreface and delta deposits. A number of new discoveries have been made in the outcrops: fragments of the arandaspid fishSacabambaspis, ossicles and moulds of the early disparid crinoidIocrinus, two new genera of conodont, an occurrence of the rare trinucleid trilobiteYinpanolithus, and palynological and sedimentological evidence of more continuous Floian–Darriwilian deposition than is usual in the region. Sea levels during Middle Ordovician time are estimated to have been 50–200 m above present levels and a wide, low-gradient shelf covered much of Arabia. Similar trace fossils and storm-dominated, micro-tidal, sedimentary rocks occur throughout the region. Small changes of sea level, possibly caused by the growth and melting of polar ice sheets, could lead to substantial seaward or landward shifts of facies belts. The Am5 deposits are thick compared to most equivalents in Arabia implying active subsidence and a ready supply of sediment.

Microendemicity in the northern Hajar Mountains of Oman and the United Arab Emirates with the description of two new species of geckos of the genus Asaccus (Squamata: Phyllodactylidae).

BackgroundThe Hajar Mountains of Oman and the United Arab Emirates (UAE) is the highest mountain range in Eastern Arabia. As a result of their old geological origin, geographical isolation, complex topography and local climate, these mountains provide an important refuge for endemic and relict species of plants and animals with strong Indo-Iranian affinities. Among vertebrates, the rock climbing nocturnal geckos of the genus Asaccus represent the genus with the highest number of endemic species in the Hajar Mountains. Recent taxonomic studies on the Zagros populations of Asaccus have shown that this genus is much richer than it was previously thought and preliminary morphological and molecular data suggest that its diversity in Arabia may also be underestimated.MethodsA total of 83 specimens originally classified as Asaccus caudivolvulus (including specimens of the two new species described herein), six other Asaccus species from the Hajar and the Zagros Mountains and two representatives of the genus Haemodracon were sequenced for up to 2,311 base pairs including the mitochondrial 12S and cytb and the nuclear c-mos, MC1R and ACM4 genes. Phylogenetic relationships were inferred using both Bayesian and maximum-likelihood approaches and the former method was also used to calibrate the phylogenetic tree. Haplotype networks and phylogenetic trees were inferred from the phased nuclear genes only. Sixty-one alcohol-preserved adult specimens originally classified as Asaccus caudivolvulus from the northern Hajar Mountains were examined for 13 morphometric and the five meristic variables using multivariate methods and were also used to diagnose and describe the two new species.ResultsThe results of the molecular and morphological analyses indicate that the species originally classified as Asaccus caudivolvulus is, in fact, an assemblage of three different species that started diversifying during the Mid-Miocene. The molecular phylogenies consistently recovered the Hajar endemic A. montanus as sister taxon to all the other Asaccus species included in the analyses, rendering the Arabian species of Asaccus polyphyletic.DiscussionUsing this integrative approach we have uncovered a very old diversification event that has resulted in a case of microendemicity, where three morphologically and ecologically similar medium-sized lizard species coexist in a very short and narrow mountain stretch. Asaccus caudivolvulus is restricted to a small coastal area of the UAE and at risk from heavy development, while the two new species described herein are widely distributed across the northern tip of the Hajar Mountains and seem to segregate in altitude when found in close proximity in the Musandam Peninsula (Oman). Similarly to other integrative analyses of Hajar reptiles, this study highlights the high level of diversity and endemicity of this arid mountain range, underscoring its status as one of the top hotspots of reptile diversity in Arabia.

Grain size and mineralogy of Al Batinah beach sediments, Sultanate of Oman

The nature of Al Batinah coast beach sediments in the Sultanate of Oman was investigated by the analysis of grain size and mineralogy. The beach sediments, mostly light-medium gray green, were predominantly fine sands, with the average grain size of all samples about 200 μm. Some of the particles were gravel (2–16 mm), and some were even larger pebble-size particles (16–256 mm). Some mud (sediment <63 μm) was present, mostly in the sub-tidal sediments. The majority of the samples were skewed to the coarse size with coarse tail partly due to the presence of shell fragments. Approximately 50 % of the beach sediments were quartz with different varieties based on shape and size. The second major component of beach sediment was calcium carbonate which varied from 10 to 65 %. The other components in decreasing order consisted of microbreccia, feldspar, pyroxene, igneous rock fragments, biotite flakes, and heavy minerals. The levels of carbonate were lower in NW Al Batinah coast from Harmul to Al Khaburah but were higher in the SE from Al Khaburah to Al Ghubrah. This could be attributed to either lower carbonate production or more sediment input by wadis along the north-western part of Al Batinah coast. The unique and complex nature of these sediments is largely due to the geology of the terrestrial source area in the Hajar Mountains which contains the famous Samail ophiolite complex and the weak sorting along the shoreline in these tide-modified beaches.

Phylogeny and biogeography of Arabian populations of the Persian Horned Viper Pseudocerastes persicus (Duméril, Bibron & Duméril, 1854)

The Persian Horned Viper (Pseudocerastes persicus) is distributed from northeast Iraq through the Iranian Plateau to western Pakistan with isolated populations in the Hajar Mountains of south-eastern Arabia. Like the other members of the genus Pseudocerastes, P. persicus is a sit-and-wait ambush feeder with low vagility, a characteristic that often results in high levels of population differentiation. In order to clarify the level of genetic variability, phylogenetic relationships, and biogeography of the Arabian populations of P. persicus we sequenced 597 base pairs of the mitochondrial cytochrome b of four individuals from the Hajar Mountains in south-eastern Arabia and inferred their phylogenetic relationships including 10 samples of P. persicus from Iran and Pakistan, four P. urarachnoides and one P. fieldi downloaded from GenBank. The four Arabian samples are genetically very similar in the gene fragment analysed and are phylogenetically very closely related to populations of P. persicus from coastal south Iran. Biogeographically, it appears that colonisation of the Hajar Mountains by P. persicus took place from Iran very recently, most probably during the last glaciation, when most of the Persian Gulf was above sea level and did not represent a barrier for dispersal.

Altitudinal variation in the diversity and structure of the desert rodent community from Jebel Al Jais, United Arab Emirates

In arid areas where organisms are subjected to environmental extremes, ecological communities are simple and provide useful models for studying community organisation. We used capture, mark and release methods between November 2014 and May 2015 to assess the rodent community in the Hajar Mountains of Ras Al Khaima along an altitudinal gradient from 460 m to 1650 m. We captured three rodent species; Arabian Spiny Mouse, Acomys dimidiatus, Wagner’s Gerbil, Gerbillus dasyurus and a Black Rat, Rattus rattus (the latter only represented by a single specimen on one occasion). The structure of rodent communities varied altitudinally with the relative abundance of Spiny Mice decreasing and Wagner’s Gerbils increasing with altitude.

Using ground-based ionisation to enhance rainfall in the Hajar Mountains, Oman

Oman is one of most water-stressed countries in the world, faced with declining reserves of fresh groundwater and the prospect of decreased natural rainfall due to climate change. A technology that can increase natural rainfall and mitigate the current and future imbalance between Oman’s demand and availability of water resources is of major interest. A rainfall enhancement trial using a ground-based ionisation technology was conducted in the Hajar Mountains in western Oman over a period of 170 days (May to October) in 2013. Data for the trial were obtained from 120 rain gauges and two automatic weather stations installed for the trial, as well as data from 11 weather stations operated by the Oman Directorate General of Meteorology and Air Navigation and the daily upper air sounding at Muscat International Airport. The trial employed a crossover design with the two ion emitters operated in a pre-determined randomised alternating schedule. Statistical analysis of the trial data was carried out using spatio-temporal models that used meteorological and spatio-temporal covariates to capture natural rainfall variation, enabling prediction of the level of rainfall that would have occurred if the ionisation emitters had not been operated. This methodology used dynamically defined target and control areas corresponding to two 30-km wide ‘corridors’ placed symmetrically about each emitter site and oriented downwind along the axis defined by the steering wind direction. Overall, a positive and significant rainfall enhancement effect attributable to the operation of the emitters was observed. The trial was continued in 2014, expanding the trial area to include four ion emitters and 149 rain gauges. Results from this year are also discussed.

Mountainous landscape vegetation and species composition at Wadi Helo: A protected area in Hajar Mountains, UAE

ABSTRACTWadi Helo (WH), in the United Arab Emirates, is a famous archeological site and protected area in the Hajar Mountains in the Arabian Peninsula. We investigated effects of topography, aspect, and altitude on floral diversity and species composition in this heterogeneous, mountainous, and highly arid environment. Using twenty transects distributed from the mountains top to the wadi bed; eighty plots, 100 m2 each, were selected for vegetation analysis. Classification of vegetation using TWINSPAN showed three groups in the wadi bed and five in the mountains, each distinguished by different dominant species. Forsskaolaea tenacissima, Rhazya stricta, Tephrosia apolina, Notoceras bicorne, Acacia tortilis, and Fagonia indica were dominants of the microhabitats of the wadi bed. Gorges were dominated with Dodonaea viscosa and Lavandula subnoda. The other four groups were found on the mountain slopes and were associated with particular aspects (being north-, south-, west-, or east-facing). The dominant species for these different aspects were, respectively: Boerhavia elegans; Ochradenus aucheri and Helianthemum lippii; Moringa peregrina; and Euphorbia larica and Cenchrus ciliaris. Altitude showed highly significant positive relationship with species frequency (P < 0.001). South-facing slopes had the highest species richness and concentration of dominance. We concluded that the distribution of dominant species was a reflection of their ecological requirements and adaptations. Seven plant species were recorded as new to the flora of the UAE. These, plus ten additional species that had been reported as rare in only one of the two published floras of the UAE were highlighted as meriting greater priority in conservation.

Climate change drives decline of Juniperus seravschanica in Oman

The southernmost population of Zeravschan juniper (Juniperus seravschanica) is found in Oman's Hajar Mountains. This is an iconic tree, important to wildlife and local people. However, Oman's juniper population is in decline: many trees have sparse, unhealthy foliage and few saplings can be found. Climate change, over-grazing, and over-harvesting have been suggested as possible causes. In this study, Zeravschan juniper were surveyed across the Jebel Akhdar-Shams range, Oman's largest juniper woodland. Generalised linear models were used to explore tree foliage status and relative abundance of saplings in relation to habitat characteristics, grazing and harvesting. Habitat characteristics associated with temperature and moisture explained patterns in percent living foliage and sapling abundance, but grazing and harvest data did not, suggesting climate change as the main cause of decline. Records of recent local temperature rises and reduced precipitation support this conclusion. Optimal habitat for juniper is now limited to areas near the summit of Oman's tallest mountain, and at lower elevations juniper with healthy foliage are only found in shallow depressions and on shaded north-facing slopes. These areas may offer climatic refugia, and protecting these habitats from other threats will be key to conserving Oman's junipers in the face of climate change.

Taxonomy and biogeography ofBunopus spatalurus(Reptilia; Gekkonidae) from the Arabian Peninsula

In the last decade, taxonomic studies have drastically increased the number of species known to inhabit the Arabian deserts. While ongoing phylogenetic studies continue to identify new species and high levels of intraspecific genetic diversity, few studies have yet explored the biogeographic patterns in this arid region using an integrative approach. In the present work, we apply different phylogenetic methods to infer relationships within the Palearctic naked-toed geckos. We specifically address for the first time the taxonomy and biogeography of Bunopus spatalurus Anderson, 1901, from Arabia using multilocus concatenated and species tree phylogenies, haplotype networks and morphology. We also use species distribution modelling and phylogeographic interpolation to explore the phylogeographic structure of Bunopus spatalurus hajarensis in the Hajar Mountains and the roles of climatic stability and possible biogeographic barriers on lineage occurrence and contact zones in this arid mountain endemism hot spot. According to the inferred topology recovered using concatenated and species tree methods, the genus ‘Bunopus’ is polyphyletic. Bunopus tuberculatus and B. blanfordii form a highly supported clade closely related to Crossobamon orientalis, while the two subspecies of ‘Bunopus’ spatalurus branch together as an independent highly supported clade that diverged during the Miocene according to our estimations. Within B. s. hajarensis, three geographically structured clades can be recognized that according to our estimations diverged during the Late Miocene to Pliocene. The paleodistribution models indicate climatic stability during the Late Pleistocene and the lineage occurrence, and predicted contact zones obtained from phylogeographic interpolation therefore probably result from the older splits of the groups when these lineages originated in allopatry. As demonstrated by the results of the multilocus molecular phylogenetic analyses and the topological test carried out in this study, the genus ‘Bunopus’ is not monophyletic. To resolve this, we resurrect the genus Trachydactylus Haas and Battersby, 1959; for the species formerly referred to as Bunopus spatalurus. Considering the morphological differences, the high level of genetic differentiation in the 12S mitochondrial gene and the results of the phylogenetic and the cmos haplotype network analysis, we elevate Trachydactylus spatalurus hajarensis to the species level Trachydactylus hajarensis (Arnold, 1980).

Population structure and ecological role of Moringa peregrina (Forssk.) Fiori. at its northwestern range edge in the Hajar Mountains

Moringa peregrina (Moringaceae), an economically important tree that occurs in arid desert mountains, is currently threatened in large part of its distribution range in the Middle East and the Arabian Peninsula. We assessed the impact of topographic factors on population structure and performance of the species at its northwest range edge on the Hafit Mountain, UAE, where it faces harsh climatic conditions and human disturbances. Size structure, fruit production, and vitality were assessed on all 165 individual plants encountered in 12 gorges. The size distribution indicates that the population of M. peregrina is young; the proportion of small and medium-size individuals is high, but with few recorded juveniles. The frequency of plant occurrence and their performance were highest at middle altitudes. Large trees produced significantly more fruits than small and medium plants, with the larger trees of the population at middle altitude producing most fruits. M. peregrina facilitated the growth of grasses and small shrubs, but limited the presence of other big shrubs and trees beneath their canopies, compared to areas beyond. The study indicates that gorges play an important role in maintaining the M. peregrina population at its hyper-arid northwest range edge.

Tracking the Oman Ophiolite to the surface — New fission track and (U–Th)/He data from the Aswad and Khor Fakkan Blocks, United Arab Emirates

The Oman Ophiolite in the United Arab Emirates (UAE) was formed in a supra-subduction zone environment at about 95Ma and was almost immediately obducted onto the eastern margin of Arabia. The timing of obduction is well constrained, but the post-obduction tectonic, uplift and exhumation history of the ophiolite and associated rocks are less well understood. We present twenty-one new fission track and (U–Th)/He analyses of apatite and zircon from the Hajar Mountains. The data show that the Oman Ophiolite had a complex exhumation history to present exposure levels in the Khor Fakkan and Aswad Blocks, resulting from at least three distinct exhumation events: 1) initial ophiolite obduction between ca. 93 and 83Ma is characterised by tectonic exhumation and rapid cooling, as revealed by zircon (U–Th)/He and apatite fission-track data, but it is not associated with major erosional exhumation; 2) data from the lower part of the ophiolite and the metamorphic sole document a second exhumation event at ca. 45–35Ma, interpreted to represent an early phase of the Zagros orogeny that led to reactivation of pre-existing structures and the differential exhumation of the Khor Fakkan Block along the Wadi Ham Shear Zone. This event led to significant erosional exhumation and deposition of a thick sedimentary succession in the Ras Al Khaimah foreland basin; and 3) Neogene exhumation is recorded by ca. 20–15Ma apatite (U–Th)/He data and a single apatite fission track date from the lowermost part of the metamorphic sole. This event can be linked to the main phase of the Zagros orogeny, which is manifested in large fans with ophiolite-derived debris (Barzaman Formation conglomerates). During this period, the metamorphic sole of the Masafi window stayed at temperatures in excess of ca. 120°C, corresponding to ca. 4km of overburden, only later to be eroded to present day levels.

DECIDUOUS FRUIT CROPS OF OMAN

Oman is located in the South Eastern part of the Arabian Peninsula. The climate is generally characterized by low rainfall (< 100 mm annually) and high temperature for most of the year. However, mountains in the northern part of the country (Hajar Mountains) reach an altitude of approximately 3,000 m a.s.l., where temperatures drops significantly to allow for the growth and cultivation of various temperate-zone fruit crops and other plants. Pomegranate is the most significant crop in this region, however, walnut, peach, apricot, fig, almond, apple and pear, also contribute significant income to the local inhabitants. Other crops of economic importance include roses and cold-climate vegetables. This paper presents an overview of the temperate fruit crops in Oman.

Landform evolution in the arid northern United Arab Emirates: Impacts of tectonics, sea level changes and climate

The interaction of wind and water may well be the key influence on the modern geomorphology of the arid regions of the world, and has had a strong influence on long-term landscape evolution in these areas. This is the case for the landforms of the northern United Arab Emirates, where aeolian landforms in the west lie on alluvial deposits, and are adjacent to fluvial landforms in the east. Even within the aeolian forms there is evidence of modern and past water activity. Modern river flow is rare and largely confined to the mountains. However, rivers and alluvial activity were more important during certain periods in the past. This study describes the landforms of the Northern Emirates (NE) and relates their form and evolution to alternating periods of arid and humid climates. The study was initially carried out to provide a background for the soil survey of the NE. Details of landform character and materials were explored during the survey, which involved detailed site and soil descriptions at 10,020 auger and Geoprobe sites (2m depth), 200 backhoe pits (2m depth), and 150 drill observations (10m depth). The main landforms identified in the study area are the Hajar Mountains, alluvial plains (fans, plains and wadis), dunes (ridges, sand veneer, rising dunes) and coastal forms. The influence of uplift and tilting of the Hajar Mountains during the Miocene and more recently is considered. Sea level changes in the Arabian Gulf are also important. The impacts of past climate change on the evolution of landforms is discussed and related to alternating periods of arid and wet climates. The north-westerly Shamal wind is primarily responsible for the formation and continued evolution of the dune fields seen in the NE today.

Phylogenetic relationships of Semaphore geckos (Squamata: Sphaerodactylidae: Pristurus) with an assessment of the taxonomy of Pristurus rupestris.

A molecular phylogeny of the sphaerodactylid geckos of the genus Pristurus is inferred based on an alignment of 1845 base pairs (bp) of concatenated mitochondrial (12S) and nuclear (acm4, cmos, rag1 and rag2) genes for 80 individuals, representing 18 of the 23-26 species, and the three subspecies of P. rupestris. The results indicate that P. rupestris is polyphyletic and includes two highly divergent clades: the eastern clade, found in coastal Iran and throughout the Hajar Mountain range in northern Oman and eastern UAE; and the western clade, distributed from central coastal Oman, through Yemen, Saudi Arabia and north to southern Jordan. Inferred haplotype networks for the four nuclear genes show that the eastern and western clades of "P. rupestris" are highly differentiated and do not share any alleles. Moreover, although the two clades are differentiated by a morphological multivariate analysis, no one character or set of characters was found to be diagnostic. Based on the molecular analysis of specimens from the type locality of P. rupestris rupestris, the name P. rupestris is applied to the eastern clade. The name that should apply to the western clade cannot be clarified until morphological and genetic data for "P. rupestris" is available from the vicinity of Bosaso, Somalia, and therefore we refer to it as Pristurus sp. 1. The phylogenetic tree of Pristurus supports the hypothesis that P. celerrimus is sister to all the other species in the analyses and that the Socotra Archipelago was independently colonized a minimum of two times.

Discussion of ‘Silicified serpentinite – a residuum of a Tertiary palaeo-weathering surface in the United Arab Emirates’

Alicja M. Lacinska and Michael T. Styles reply: We appreciate the comment by C. R. M. Butt on the publication by Lacinska &amp; Styles (2013) on the silicified serpentinites described from the Hajar Mountains in the United Arab Emirates. This comment is based on his very extensive knowledge of laterites and regoliths from ancient shield areas around the world; the degree to which this knowledge is directly applicable to the rocks formed at the margins of a recently uplifted mountain range, as described in the original paper, is debatable.

Near-surface diagenesis of ophiolite-derived conglomerates of the Barzaman Formation, United Arab Emirates: a natural analogue for permanent CO 2 sequestration via mineral carbonation of ultramafic rocks

Abstract Carbon capture and storage by mineralization is a potential method for storing anthropogenic CO 2 emissions, and is based on the reaction between Mg silicate and CO 2 to form Mg carbonate. The conglomerates of the Barzaman Formation exposed in the eastern United Arab Emirates represent an excellent natural analogue of this process. These conglomerates were deposited as a series of alluvial fans along the western margin of the Hajar Mountains, part of the Oman-UAE Ophiolite, and are composed largely of ultramafic and lesser-mafic clasts. The clasts and matrix have been extensively altered to dolomite during diagenetic processes. Analysis and interpretation of rock textures provide evidence for the various factors that influenced the diagenetic processes and shed light on the silicate–carbonate transformation process. All the reactions have taken place in the near-surface environment; the silicate–carbonate conversion reaction is exothermic and occurs spontaneously at near-ambient pressure and temperature, probably no greater than 50 °C. Estimates of the amount of CO 2 stored in this way can be obtained from considerations of outcrop area, formation thickness and percentage of dolomite replacement, and show that c. 150 billion tonnes (equivalent to about 4 years of worldwide CO 2 emissions at current rates) are stored.

Discussion of ‘Silicified serpentinite – a residuum of a Tertiary palaeo-weathering surface in the United Arab Emirates’

C. R. M. Butt comments: In their recent paper, Lacinska &amp; Styles (2013) described in detail the geological setting, mineralogy and petrology of ‘silicified serpentinite’ in the Hajar Mountains, United Arab Emirates (UAE). They note that their ‘silicified serpentinite’ is essentially the same unit as ‘birbirite’ and other informally named quartz-rich outcrops that overlie ultramafic rocks in this and other regions. Some authors have suggested such silicification to be hydrothermal in origin, but it is now generally accepted to be due to weathering. Lacinska &amp; Styles (2013) concluded that ‘silicified serpentinite’ is a silcrete; this is correct, but it is a purely descriptive term and, without qualification, has no specific genetic implications other than being silica-cemented regolith (Butt &amp; Zeegers, 1992; Eggleton, 2001). The materials illustrated are more correctly termed a silicified saprolite as they preserve the fabric of the protolith.

An early MIS 3 pluvial phase in Southeast Arabia: Climatic and archaeological implications

Climatic changes in Arabia are of critical importance to our understanding of both monsoon variability and the dispersal of anatomically modern humans (AMH) out of Africa. The timing of dispersal is associated with the occurrence of pluvial periods during Marine Isotope Stage (MIS) 5 (ca. 130–74 ka), after which arid conditions between ca. 74 and 10.5 ka are thought to have restricted further migration and range expansion within the Arabian interior. Whilst a number of records indicate that this phase of aridity was punctuated by an increase in monsoon strength during MIS 3, uncertainties regarding the precision of terrestrial records and suitability of marine archives as records of precipitation, mean that the occurrence of this pluvial remains debated. Here we present evidence from a series of relict lake deposits within southeastern Arabia, which formed at the onset of MIS 3 (ca. 61–58 ka). At this time, the incursion of monsoon rainfall into the Arabian interior activated a network of channels associated with an alluvial fan system along the western flanks of the Hajar Mountains, leading to lake formation. Multiproxy evidence indicates that precipitation increases intermittently recharged fluvial systems within the region, leading to lake expansion in distal fan zones. Conversely, decreased precipitation led to reduced channel flow, lake contraction and a shift to saline conditions. These findings are in contrast to the many other palaeoclimatic records from Arabia, which suggest that during MIS 3, the latitudinal position of the monsoon was substantially further south and did not penetrate the peninsula. Additionally, the occurrence of increased rainfall at this time challenges the notion that the climate of Arabia following MIS 5 was too harsh to permit the further range expansion of indigenous communities.

A review of the geckos of the genus Hemidactylus (Squamata: Gekkonidae) from Oman based on morphology, mitochondrial and nuclear data, with descriptions of eight new species

The genus Hemidactylus is one of the most species-rich and widely distributed of all reptile genera, being found in thetropical and subtropical regions of the world and hundreds of continental and oceanic islands. Despite having already 111species, the number of species described in recent years is very high. This has been facilitated, in part, by the use ofmolecular techniques, which in most cases have been employed to confirm the differentiation at the DNA level of somemorphologically variable forms and to discover some cryptic lineages.Preliminary analyses indicate that some Hemidactylus species from Oman are quite variable in their morphologyand may include more than one species. In order to test this hypothesis we inferred a molecular phylogeny including 131Hemidactylus (20 species) using 1385 base pairs of mitochondrial DNA (353 bp 12S; 302 bp cytb; 588 bp nd4 and 142bp tRNAs) and 1481 bp of nuclear DNA (403 bp c-mos; 668 bp mc1r and 410 bp rag2) and analyzed 226 specimens (15species) for several meristic and pholidotic characters of which we took 3103 photographs that have been deposited inMorphoBank (project 483). Our results indicate the presence of eight new species of Hemidactylus geckos in Arabia: H.luqueorum sp. nov. and H. hajarensis sp. nov. from North Oman; H. masirahensis sp. nov. from Masirah Island; H.inexpectatus sp. nov. from one locality on coastal Central Oman; H. alkiyumii sp. nov., H. festivus sp. nov. and H.paucituberculatus sp. nov. from Dhofar, Southern Oman; and finally H. endophis sp. nov. probably from North Omanand described on the basis of morphology alone. An identification key to the genus Hemidactylus from Oman is alsopresented. With these descriptions, the number of Hemidactylus species found in Oman increases from 7 to 13 and thenumber of endemic Hemidactylus from 0 to 6. The description of three new species endemic to the Hajar Mountains inNorth Oman highlights the importance of this mountain range as a biodiversity hotspot that, up to now, includes 12reptile species that are found nowhere else in the World. Another hotspot of Hemidactylus biodiversity is the DhofarMountain range, in the extreme Southwestern corner of Oman and East Yemen. As a result of its particular geographicsituation, orography and the effect of the Southwest Monsoons, this mountain range presents a diverse variety of habitatswith different species of Hemidactylus adapted to them.With the exception of H. flaviviridis and H. leschenaultii, which belong to the Tropical Asian clade of Hemidactylus,all Arabian Hemidactylus for which DNA sequence is available are members of the Arid clade of Hemidactylus.Relatively recent dispersal appears to have taken place within Arabia in the H. turcicus group, with the South Arabian H.lemurinus occurring far from other confirmed members of this assemblage. Hemidactylus flaviviridis and a clade of H. robustus are genetically uniform, widespread in Arabia and beyond and occur around human habitations, suggesting thatmuch of their large distributions are anthropogenic, as appears to be so in several other Hemidactylus species outsideArabia.The way in which species of Arabian Hemidactylus separate ecologically is surprisingly varied. They may occur atsimilar altitudes but replace each other geographically, or if they are sympatric there may be altitudinal separation.Humidity may also be an important factor, and when animals exist within a few meters of each other, structural nichemay be significant. While four native species occur close together in Dhofar, most Hemidactylus communities in Arabiaconsist of only one or two species, although climbing geckos belonging to other genera, such as Asaccus and Ptyodactylus, may also be present.‫غ‬