High Mountain Range Research Articles

Deformation patterns and potential active movements of the Fansipan mountain range, northern Vietnam

Located in northern Vietnam, the Fansipan mountain range is the highest topography in the Indochina area. Until recently, there has been limited research regarding the tectonic deformation of the Fansipan mountain range and whether there are notable surface ruptures or active faults in the area. This study provides the first insight into the deformation patterns and potential active movements of the Fansipan mountain range, and may improve our understanding of the overall tectonic activities in northern Vietnam. Our observations from ASTER 30-m DEM show a symmetrical mountain form in the north and an asymmetrical form in the south. The analysis of river profiles indicates similar patterns on both sides in the north and different patterns in the south with short and steep rivers on the SW side and long and gentle rivers on the NE side. The results of the normalized steepness index (ksn) also show higher values on the SW side of the south part than the values from the other sides. These results suggest a spatial variation in rock uplift patterns of the Fansipan mountain range. Notably, the mountain front of the SW side of the southern Fansipan mountain range is associated with the Phong Tho-Nam Pia normal fault, suggesting that the normal faulting activity likely played an important role in tectonic uplift of this high mountain range. Our investigation of the stress field using fault kinematics indicates that the Fansipan mountain range and its surrounding areas are undergoing an inhomogeneous mixture of strike-slip and normal faulting. It is proposed that the strike-slip and normal motions alternated because of a permutation of σ1/σ2 under the same extensional stress regime of approximately NE–SW σ3. This kinematic pattern may effectively control the recent tectonic movements in northern Vietnam.

Survival of the Qaidam mega-lake system under mid-Pliocene climates and its restoration under future climates

Abstract. The Qaidam Basin in the north of the Tibetan Plateau has undergone drastic environmental changes during the last millions of years. During the Pliocene, the Qaidam Basin contained a freshwater mega-lake system although the surrounding regions showed increasingly arid climates. With the onset of the Pleistocene glaciations, lakes began to shrink and finally disappeared almost completely. Today, hyperarid climate conditions prevail in the low-altitude parts of the Qaidam Basin. The question of how the mega-lake system was able to withstand the regional trend of aridification for millions of years has remained enigmatic so far. This study reveals that the mean annual water balance, i.e. the mean annual change in terrestrial water storage in the Qaidam Basin, is nearly zero under present climate conditions due to positive values of net precipitation in the high mountain ranges and shows positive annual values during warmer, less dry years. This finding provides a physically based explanation for how mid-Pliocene climates could have sustained the mega-lake system and that near-future climates not much different from present conditions could cause water storage in reservoirs, raising lake levels and expanding lake areas, and may even result in restoration of the mega-lake system over geological timescales. The study reveals that a region discussed as being an analogue to Mars due to its hyperarid environments is at a threshold under present climate conditions and may switch from negative values of long-term mean annual water balance that have prevailed during the last 2.6 million years to positive ones in the near future.

Barrier winds in the Italian region and effects of moist processes

Barrier winds form when a sufficiently high mountain range causes a stratified airflow directed towards the orographic barrier to slow down at the low levels, producing a pressure imbalance, which in turn generates a mountain-parallel wind. The present study analyses barrier wind occurrence in the Italian region and surrounding seas from both a climatological and dynamical perspective. The main goals are to assess the applicability of the linear theory of upstream blocking to real-world cases and to investigate the role of atmospheric moist processes in promoting the formation and influencing the evolution of barrier winds. A 2-year climatology of barrier winds reveals that they occur more frequently than the opposite regime of flow over the orography, especially in the cold season. Barrier wind events are found to be associated with an upstream flow having a significantly higher inverse Froude number (or non-dimensional mountain height) values than flow-over events on average, consistently with the theory. An Alpine case study is simulated using numerical models and sensitivity tests are performed to investigate the dependence of barrier wind development and properties on the non-dimensional mountain height. Simulations reveal the strong influence of precipitation-related diabatic processes on the development of an upstream cold pool, which in turn supports barrier wind maintenance and strengthens its intensity. Idealized numerical experiments with varying upstream flow moisture shed light on processes leading to significant strengthening of barrier wind intensity, in particular on the crucial role of latent heat exchanges associated with precipitation.

Estimating glacier-bed overdeepenings as possible sites of future lakes in the de-glaciating Mont Blanc massif (Western European Alps)

De-glaciating high mountain areas result in new landscapes of bedrock and debris where permafrost can degrade, persist or even newly form in cases, and of new lakes in glacier bed overdeepenings (GBOs) becoming ice-free. These landscapes with new lakes in close neighborhood to over-steepened and perennially frozen slopes are prone to chain reaction processes (e.g. rock-ice avalanches into lakes triggering impact waves, dam breach or overtopping, and debris flows) with potentially far-reaching run-out distances causing valley floors devastation. The frequency, magnitude and zonation of hazards are shifting, requiring integrative approaches combining comprehensive information about landscape evolution and related processes to support stakeholders in their adaptation strategies. In this study, we intend to setup an essential baseline for such an integrative approach in the Mont Blanc massif (MBM), which is a typical high-mountain range affected by de-glaciation processes. We first (i) predict and (ii) detect potential GBOs by combining the GlabTop model with a visual analysis based on morphological indications of glacier flow through over-deepened bed parts. We then (iii) determine the level of confidence concerning the resulting information, and (iv) estimate the approximate time range under which potential lakes could form. The location of the predicted GBOs and the shape of glacier beds are evaluated against currently forming water bodies at retreating glacier snouts, and seismic and ice penetrating radar measurements on the Argentière glacier. This comparison shows that the location of predicted GBOs is quite robust whereas their morphometric characteristics (depth, volume) are highly uncertain and tend to be underestimated. In total, 48/80 of the predicted or detected GBOs have a high level of confidence. In addition to five recently formed water bodies at glacier snouts, one of the high confidence GBOs (Talèfre glacier) which is also the most voluminous one could form imminently (during coming years), if not partially or totally drained through deeply incised gorges at the rock threshold. Twelve other lakes could form within the first half of the century under a constant or accelerated scenario of continued glacier retreat. Some of them are located below high and permanently frozen rock walls prone to destabilization and high-energy mass movements, hinting at possible hot spots in terms of hazards in the coming decades, where more detailed analysis would be required.

The oldest managed aquifer recharge system in Europe: New insights from the Espino recharge channel (Sierra Nevada, southern Spain)

In Sierra Nevada (southern Spain), the highest mountain range in southern Europe, the application of an ancestral Integrated Water Resources Management system (IWRM), based on the conjunctive use of groundwater and surface water, provides water resources for irrigation and supply in the driest months of the year in this semiarid mountain region. Meltwater is derived from the headwaters of the mountain streams and rivers through a set of uncoated channels excavated in the ground (locally known as acequias de careo) to infiltrate at the upper part of the valleys. Water infiltrated along the acequias de careo slowly flows down the hillsides, through the weathered zone of the hard rock aquifer and the glacial and periglacial sediments. The recharge accomplished through this Managed Aquifer Recharge technique (MAR) activates numerous springs located halfway down the hillside and increases the base flow of the rivers. In this study, focused on a careo channel located on the southern slope of Sierra Nevada called Acequia de El Espino, different archaeological, sedimentological, geophysical and hydrogeological techniques are applied to determine the age and the efficiency of this ancestral example of a MAR and IWRM system. Results suggest that the acequias de careo may be the oldest MAR system in Europe, and that this MAR technique could be applied in other high mountain alpine watersheds to mitigate the effects of climate change.

Amphibian community structure along elevation gradients in eastern Nepal Himalaya

BackgroundSpecies richness and composition pattern of amphibians along elevation gradients in eastern Nepal Himalaya are rarely investigated. This is a first ever study in the Himalayan elevation gradient, the world’s highest mountain range and are highly sensitive to the effects of recent global changes. The aim of the present study was to assess amphibian community structure along elevation gradients and identify the potential drivers that regulate community structures. Amphibian assemblages were sampled within 3 months in both 2014 and 2015 (from May to July) using nocturnal time constrained and acoustic aids visual encounter surveys. In total, 79 transects between 78 and 4200 m asl were sampled within 2 years field work. A combination of polynomial regression, generalized linear models, hierarchical partitioning and canonical correspondence analysis were used to determine the effects of elevation and environmental variables on species richness, abundance, and composition of amphibian communities.ResultsSpecies richness and abundance declined linearly with increasing elevation, which did not support the Mid-Domain Model. Among all the environmental variables, elevation, surface area and humidity were the best predictors of species richness, abundance and composition of amphibians. The majority of amphibian species had narrow elevation ranges. There was no significant correlation between species range size and elevation gradients. However, body size significantly increased along elevation gradients, indicating that Bergmann’s rule is valid for amphibians in eastern Nepal Himalaya.ConclusionsThis study indicates that eastern Nepal Himalaya is a hotspot in amphibian diversity, and it should be served as a baseline for management and conservation activities.

La connectivité sédimentaire dans la haute chaîne pyrénéenne par l’analyse de la crue de juin 2013 : le rôle des formations superficielles

L' (in)efficacite du couplage versant/lit est particulierement mise en lumiere lors d' evenements hydro-climatiques extremes. La crue majeure de juin 2013 dans les Pyrenees centrales a montre le role des formations superficielles dans la constitution de la charge solide des ecoulements. En zone de montagne, les parametres morphometriques sont egalement une variable de controle de la connectivite sedimentaire. Dans cette etude, la dynamique sedimentaire de la crue est etudiee sur les quatre bassins versants qui ont ete les plus marques par la crue. L'analyse se fonde sur le calcul d'un indice morphometrique de connectivite sedimentaire realise a partir d'un MNT, qui est ensuite croise avec la cartographie des formations superficielles et des zones actives lors de la crue. Cette methodologie permet de comparer la connectivite theorique/structurelle des sous-bassins versants et formations superficielles a la connectivite reelle/fonctionnelle lors de la crue. A la difference des grandes crues historiques passees, cette comparaison fait ressortir la faible contribution des bassins tributaires de petite taille qui possedent pourtant une connectivite sedimentaire theorique importante. Les tetes de bassins et les depots du domaine glaciaire et periglaciaire n' ont pas fourni de materiaux lors de la crue et sont des zones deconnectees. A contrario, les depots post-glaciaires adjacents au reseau hydrographique du fond de vallee sont les plus connectes et les plus contributifs. En effet, la connectivite sedimentaire laterale se realise principalement entre les formations superficielles de bas de versant de moyenne et basse vallee, adjacents au collecteur principal. Notre etude souligne le potentiel de l'indice morphometrique appuye par la cartographie geomorphologique pour caracteriser la connectivite sedimentaire de la haute chaine pyreneenne en contexte d' evenement majeur.

A suite of new plant records from the Sierra de San Pedro Mártir, Baja California, Mexico

Ninety-two southernmost plant distribution records were documented on an expedition in 2016 to a remote meadow at the southern end of the Sierra de San Pedro Mártir, the highest mountain range in Baja California, Mexico. Among these new records, there are 12 additions to the known high elevation flora. Noteworthy new populations were documented for 14 regionally endemic plants, and several collections of rare or rarely collected taxa were also significant. Our findings suggest that the Santa Rosa Meadow should be targeted for biodiversity conservation efforts, with an emphasis on managed grazing, to support the recovery of rare meadow-endemic taxa.

Non-native Minnows Threaten Quillwort Populations in High Mountain Shallow Lakes

Submersed aquatic plants are a key component of shallow, clear water lakes contributing to primary production and water quality. High mountain lakes are naturally fishless although invasive trout and most recently minnows have been introduced causing a major impact on fauna richness. The Pyrenean high mountain range has preserved soft-water oligotrophic boreal isoetids in their southern limit of distribution but the recent fish introduction is a potential factor of stress that needs to be addressed. We here work under the hypothesis that due to contrasting ecological features, trout will not be heavily affecting quillwort populations while minnows will have a stronger effect on zooplankton and zoobenthos that will promote algal growth and reduce light availability for the underwater meadows. Ten Pyrenean shallow lakes representative of three scenarios -fishless, with trout and with minnows-, were sampled for meadow structure, water column and benthic environment characterization in mid-summer 2015 and 2016. Quillwort biomass allocation (above vs. belowground), epiphytic load, and composition of the algal community (abundant cyanobacteria) differed in the presence of minnows. In trout lakes biomass allocation and epiphytic load were average and the algal community composed by chlorophytes and diatoms as in fishless lakes. Biomass ratio was close to thresholds of negative buoyancy in minnow lakes indicating that meadows were at risk of uprooting and consequent de-vegetation. Total and soluble carbohydrates were lower and the sporangia contained significantly less reserves to constrain growth and expansion in the presence of minnows. Lake scenarios were coupled to physicochemical differences with low light, high phosphorus and Chl-a (mesotrophia) in minnow lakes, while trout and fishless lakes remained oligotrophic. This is the first study assessing the impact of non-native fish on soft-water isoetids from mountain lakes and shows that minnows are a major threat to quillworts. The impaired light environment (from epiphytic algal overgrow and water column Chl-a) entails consequent regression (i.e., no recruitment) and de-vegetation (uprooting) of the meadows. Since soft-water oligotrophic mountain lakes are protected under the Habitats Directive, some action needs to be urgently implemented not only to preserve quillworts but to the overall ecological integrity of the lakes.

Preservation Strategies for Southern Morocco’s At-Risk Built Heritage

Morocco has a vernacular architectural heritage of recognized value, which constitutes an indissoluble part of its cultural legacy. In the south of the country, specifically in the High Atlas mountain range and the pre-Saharan oases, we mainly find earth constructions of an incomparable landscape integration and plasticity. However, the political and social changes of the last decades are favoring the abandonment of these constructions, placing many of them at risk of disappearing. The objective of this contribution is to reveal the characteristics and weaknesses that the new constructions present today. The method used has consisted in analyzing the preservation actions that are being carried out, both by the Moroccan public administration and by private individuals, including those developed by the authors through documentation, cataloging, virtualization, and restoration.

Dynamics of natural conditions around modern glaciation location at the Eastern Sayan

Mountain massif Munku-Sardyk presents the highest mountain range and adjacent Stanovoy ridge highlands of the Eastern Sayan. There is situated modern glaciation site which was the most studied in the course of last 160 years. This periglacial area experienced different periods of cooling and warming in the Holocene and retained traces of the Sartan glaciation of Subboreal (3000–5000 years ago), the Little Ice Age, the evidences of Holocene optimum and general warming last time. The authors examined the variability of activity of modern glaciation and variation of natural conditions of the periglacial zone on climate and on dendrochronological data. Results of larch and Siberian stone pine growth data were revealed at the higher border of forest communities. Analysis of the growth of the “fossil” tree in the Holocene optimum showed that the absolute magnitude of its increment was two times higher than for up-to-date long-lived trees. Identified periods of the Peretolchin glacier retreat in 1900–1965 and 1983–2000 years took place with increased growth of trees and the rate of sedimentation in proglacial lake, and vice versa glacier advance on in 1965–1980 years was accompanied by slowing of tree increments and reduction in sedimentation rate. Since 2000, there has been growth of trees instability associated with a decrease in average monthly summer temperatures.

Systematics, biogeography and evolution of Asaccus gallagheri (Squamata, Phyllodactylidae) with the description of a new endemic species from Oman

The Hajar Mountains are the highest mountain range in eastern Arabia. Despite being classified as a mountain desert, it is considered one of the top biodiversity hotspots of Arabia. As a result of its relatively old geological origin, complex topography, environmental heterogeneity and geographic isolation from other mountain ranges, its fauna and flora have diversified significantly producing high levels of endemicity, particularly amongst reptiles. Several genetic studies indicate that this diversity may still be underestimated, especially within some groups containing morphologically similar species like the nocturnal geckos of the genus Asaccus. These have radiated extensively on both sides of the Gulf of Oman, in the Hajar Mountains and the Zagros Mountains of south-west Asia, and are a good example of the faunal affinities between these two mountain ranges. In the present work, we analyse A. gallagheri, the smallest species of the Arabian radiation, using an unprecedented sampling across its entire distribution range and an integrative approach combining morphological, macroecological and multilocus molecular data with the objective of clarifying its systematics and phylogeography. The results support the presence of two allopatric species within A. gallagheri that split approximately 6 Ma. The newly discovered species is endemic to the Eastern Hajars and is described herein mainly on the basis of its smaller size and high genetic divergence from A. gallagheri. The molecular analyses also uncovered remarkable levels of genetic diversity within both species. The present study highlights the diversity of the genus Asaccus in south-east Arabia and stresses its relevance from a conservation point of view.http://www.zoobank.org/urn:lsid:zoobank.org:pub:62EB3146-9F79-4857-8CC6-36FE235D84D4

Calls distinguish species of Antbirds (Aves: Passeriformes: Thamnophilidae) in the genus Pyriglena

Populations in the genus Pyriglena Cabanis, 1847, commonly known as fire-eyes, are patchily distributed in central South America from the Pacific slope of the Andes to the Atlantic Forest of Brazil. Pyriglena populations are currently placed into 12 taxa, only five of which are not isolated from their neighbors by distance, a high mountain range, or a major river. In the Thamnophilidae, taxonomic decisions regarding such allopatric populations have primarily rested on differences in vocalizations, thought not to be learned and to play a key role in the speciation process. When we examined Pyriglena vocalizations in this context, the outcomes revealed substantial diversity in their calls, rather than their songs. They commonly delivered four different types of calls, unusual although not unprecedented in thamnophilids. Diversity in calls rather than songs underscores the need to consider all vocalizations in taxonomic studies. The outcomes support the continued recognition of the White-shouldered Fire-eye Pyriglena leucoptera (Vieillot) and Fringe-backed Fire-eye Pyriglena atra (Swainson) as distinct species, and indicate that, in addition, the currently constituted Pyriglena leuconota should be considered three species: the Western Fire-eye Pyriglena maura (Ménétries); the Tapajos Fire-eye Pyriglena similis Zimmer; and the East Amazonian Fire-eye Pyriglena leuconota (von Spix). We also identify taxonomic uncertainties regarding subspecies that require acquisition of additional data and further analysis.

Relationships between vegetation, air and soil temperatures on Norwegian mountain summits

ABSTRACTGeographic variations in air and soil temperatures are dependent on several biotic and abiotic factors. Air temperature has mostly been used to characterize thermal conditions for plant life, and studies of bioclimatic gradients. From a biological point of view, it is also essential to know to what extent soil temperature is coupled with air temperature. In this study, we have quantified the deviations between soil and air temperatures along gradients in latitude, altitude, and possible effects of the vegetation. Sixteen different temperature variables were estimated from 49 vegetation plots on 19 mountain summits along the high mountain range in Norway, ranging from 230 to 1780 m a.s.l., and from 59°N to 71°N. Soil and air temperature variables were estimated from the study plots during one year. All air and soil temperature variables were significantly correlated, but the rate of explanation was mostly relatively low (37.0–60.0%), except during the growing season. Start of the growing season, determined by air or soil temperatures, could deviate by 38 days mainly due to effects of frozen soils. Vegetation composition, especially the lichen cover, had a major impact on soil temperature, Dwarf shrub cover increased significantly with increasing July temperature. Lichen abundance and degree of soil frost were strongly correlated, and explained a major part of the variation in soil temperatures. The study indicates that air temperature is generally a poor proxy for soil temperature in cold areas, except during July.

Neanura judithaen. sp. from Polish Carpathians, with an updated and illustrated key to all species of the genusNeanuraMacGillivray, 1893 (Collembola: Neanuridae)

ABSTRACT One new species belonging to the genus Neanura MacGillivray, 1893 was found during taxonomic investigations of Tatra Mts, the highest mountain range in the Carpathians. Neanura judithae n. sp. is characterized by the conspicuous reduction of chaetotaxy on dorsal side of the body. It is closely related to the sympatric species N. parva (Stach, 1951), from which it differs in having a non-ogival labrum (vs ogival in N. parva) and complete fusion of tubercles Di on the abdominal segment V(vs incomplete in N. parva). Furthermore, the new species is distinguished by absence of chaetae De3 on abdominal terga I-III and 2 + 2 chaetae Di on abdomen V. An illustrated description and short remarks on the ecology of N. judithae n. sp. are presented. Additionally, data on morphology of all known species of the genus are also provided in the key.

Early 21st century glacier thickness changes in the Central Tien Shan

Although studies based on satellite gravimetry (2003−2010) and laser altimetry (2003–2009) measurements have achieved region-wide glacier mass change for the Tien Shan, the dynamic process of glacier yet to be closely monitored and understood so that its impact can be assessed accurately. In this study, we investigated region-wide glacier thickness change in the Central Tien Shan (CTS) during 2000–2012 by differencing the Shuttle Radar Topographic Mission (SRTM) digital elevation model (DEM) with a newly constructed DEM from 27 TanDEM-X images. For a total glacier area of 7239.8±527.2km2, an average glacier thickness change rate of −0.24±0.22m/a was derived. This result agrees well with the result based on satellite laser altimetry measurements reported earlier (−0.31±0.41m/a). With temporal synchronization, a fine spatial resolution and wide coverage, our measurements are able to reveal abundant glacier change features and dependencies in the CTS. Firstly, the lower mountains have seen a more severe glacier decline, and the glaciers facing the prevailing wind (westerlies) have experienced a greater decline because of the stronger evaporation. Furthermore, those glaciers lying along the extremely high Meridian mountain range have obviously gained mass in their upper reaches, because the air current from the west is blocked and lifted by the Meridian mountain range. Secondly, for the entire glacier body, the theoretical hyperbolic dependence between debris thickness and ice decline was very difficult to establish. Some huge glaciers covered by heavy debris have still experienced a severe decline. However, even though the heavy debris did not prevent the ablation, its attenuating effects were considerable. Thirdly, for the glaciers that surged before 2000, the mass gain in the restoring zones has not been enough to cover the mass loss in ablation zones. Some large glaciers surged again during 2000–2012; however, with much lower magnitudes than in previous surges. In general, the surge glaciers have experienced a greater decline than the non-surge glaciers. Fourthly, due to the ice front calving and subglacial thermal erosion, glaciers connected to proglacial lakes have receded and thinned much more rapidly than the land-terminated glaciers. Overall, the glaciers in the CTS are more stable than those in other parts of the Tien Shan. However, the glacier state there is still alarming. A moderate average thinning rate was derived because the drastic thinning in the ablation zones was balanced by the slight thinning in the broad accumulation zones.

Early- to mid-Holocene forest-line and climate dynamics in southern Scandes mountains inferred from contrasting megafossil and pollen data

The result of 344 radiocarbon-dated megafossils is here presented and discussed. This study aims at elucidating early- to mid-Holocene forest-line and climate dynamics in the southern Scandes along a present gradient of decreasing forest-line elevations. Around 9.5 calibrated ka before present (BP), pine suddenly established vertical belts of at least 200 m. These represent the highest pine-forests during the Holocene, ca. 210–170 m higher than today when corrected for land uplift. By this, summer temperatures at least 1–1.3°C warmer than today are indicated for the early Holocene thermal maximum around 8.5–9.5 cal. ka BP. The most pronounced warming occurred in Jotunheimen, the highest mountain range in Scandinavia, because of an amplified ‘Massenerhebung’ effect. Megafossils show the establishment of birch-forests above pine-forests already from the early Holocene. Pine-forests started their decline in the early Holocene and became replaced by the less warmth-demanding birch-forests. Pine megafossil results and pollen studies from the same areas show that cooling around 8.5 cal. ka BP caused a significant decrease in pine pollen production whereas pine-forest-lines were more or less unaffected. In the following period of about 2000 years, the high-altitudinal pine-forests could hardly be detected in pollen diagrams. This shows how strongly past temperatures influenced on the pollen production of individuals and how this might obscure pollen-based reconstructions of past vegetation. To be able to correct for this error, there is a need for establishing exact present-day relationships between temperature and pollen production of prolific pollen producers.

Morphological evolution of gold nuggets in proximal sedimentary environments, southern New Zealand

A rare collection of centimetre-scale proximal gold nuggets has been examined in the context of the Late Pleistocene to Holocene eluvial and colluvial sediments in which they occur, in a range of environments from arid temperate to periglacial. Liberation of supergene nuggets from their basement source in fault zones occurred progressively by physical erosion as the host basement rocks were uplifted between middle Miocene and Holocene. The host sediments are made up of poorly sorted angular greenschist facies schist debris. Some nuggets were recycled through several generations of these colluvial deposits, and additional nuggets were liberated to younger sediments during this time. The nuggets did not migrate laterally more than a few tens of metres during this repeated recycling, and were passively elevated vertically with the rising basement on to the crest and slopes of a 1600m high mountain range. The most recently liberated nuggets retain almost all the morphological features of their supergene origin, including coarse (cm scale) crystal shapes, delicate crystalline internal structure, and imprints of oxidised pyrite crystals. Minor transport in colluvium has caused some abrasion and rounding of gold crystals. Repeated recycling progressively obscured the crystal shapes, although relict crystals are still recognisable on parts of most nuggets. Differential timing of liberation from basement has resulted in a wide range of rounding effects in groups of closely-coexisting nuggets. Variably crystalline gold overgrowths (micron scale) coat abraded surfaces of all or part of most nuggets, commonly intergrown with authigenic smectite clay minerals. These overgrowths developed from alkaline groundwater (pH7–9) that had undergone extensive chemical interaction with labile minerals in the host colluvium. Abrasion during recycling removed some of the overgrowths, but this was replaced in the new sedimentary hosts. Physical and chemical processes affecting nuggets in these sediments have similarly affected eluvial and colluvial nuggets in a wide range of settings around the world, including Yukon (Canada), California (USA) and arid parts of Australia.

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.

Pre-Holocene Origin for the Coronopus navasii Disjunction: Conservation Implications from Its Long Isolation.

Integration of unexpected discoveries about charismatic species can disrupt their well-established recovery plans, particularly when this requires coordinate actions among the different governments responsible. The Critically Endangered Coronopus navasii (Brassicaceae) was considered a restricted endemism to a few Mediterranean temporary ponds in a high mountain range of Southeast Spain, until a new group of populations were discovered 500 km North in 2006. Ten years after this finding, its management has not been accommodated due to limited information of the new populations and administrative inertia. In this study, DNA sequences and species distribution models are used to analyse the origin of the C. navasii disjunction as a preliminary step to reassess its recovery plan. Molecular results placed the disjunction during Miocene-Pleistocene (6.30–0.49 Mya, plastid DNA; 1.45–0.03 Mya, ribosomal DNA), which discards a putative human-mediated origin. In fact, the haplotype network and the low gene flow estimated between disjunct areas suggest long-term isolation. Dispersal is the most likely explanation for the disjunction as interpreted from the highly fragmented distribution projected to the past. Particularly, a northward dispersal from Southeast is proposed since C. navasii haplotype network is connected to the sister-group through the southern haplotype. Although the reassessment of C. navasii conservation status is more optimistic under the new extent of occurrence, its long-term survival may be compromised due to the: (1) natural fragmentation and rarity of the species habitat, (2) genetic isolation between the two disjunct areas, and (3) northward shift of suitable areas under future climate change scenarios. Several ex-situ and in-situ conservation measures are proposed for integrating Central East Spanish populations into the on-going recovery plan, which still only contemplates Southeast populations and therefore does not preserve the genetic structure and diversity of the species.