Hoggar Mountains Research Articles

Antibacterial and antibiofilm properties of two cyclic dipeptides produced by a new desert Streptomyces sp. HG-17 strain against multidrug-resistant pathogenic bacteria.

The emergence of multidrug-resistant bacteria and biofilms requires discovering new antimicrobial agents from unexplored environments. This study aims to isolate and characterize a new actinobacterial strain from the Hoggar Mountains in southern Algeria and evaluate its ability to produce bioactive molecules with potential antibacterial and antibiofilm activities. A novel halotolerant actinobacterial strain, designated HG-17, was isolated from the Hoggar Mountains, and identified based on phenotypic characterizations, 16S rDNA sequence analysis, and phylogenetic analysis. The antibacterial and antibiofilm activities of the strain were assessed, and the presence of biosynthetic genes (PKS-I and NRPS) was confirmed. Two active compounds, HG-7 and HG-9, were extracted butanol solvent, purified by HPLC, and their chemical structures were elucidated using ESI mass spectrometry and NMR spectroscopy. The strain HG-17 was identified as Streptomyces purpureus NBRC with 98.8% similarity. It exhibited strong activity against multidrug-resistant and biofilm-forming bacteria. The two purified active compounds, HG-7 and HG-9, were identified as cyclo-(d-cis-hydroxyproline-l-phenylalanine) and cyclo-(l-prolone-l-tyrosine), respectively. The minimum inhibitory concentrations (MICs) of HG-7 and HG-9 ranged from 3 to 15 μg/mL, comparable to the MICs of tetracycline (8 to 15 μg/mL). Their minimum biofilm inhibitory concentration (MBIC 50%) showed good inhibition from 48.0 to 52.0% at concentrations of 1 to 7 μg/mL against the tested bacteria. This is the first report of cyclo-(d-cis-hydroxyproline-l-phenylalanine) and cyclo-(l-prolone-l-tyrosine) antibiotics from S. purpureus and their anti-multi-drug-resistant and biofilm-forming bacteria. These results indicate that both antibiotics could be used as effective therapeutics to control infections associated with multidrug-resistant bacteria.

Mahomedella hoggarensis sp. n. (Lepidoptera, Cossidae, Cossinae) from Southern Algeria

The article describes Mahomedella hoggarensis sp. nov. distributed in the Hoggar Mountains (Southern Algeria). For the first time, the female genitalia of genus Mahomedella Yakovlev, 2011 (Lepidoptera, Cossidae: Cossinae) are described. The map of the genus distribution is given. The article has seven illustrations.

Origin and Evolution of Synoptic-Scale Vortices Initiated at Low Level Downwind of the Hoggar Mountains

Abstract Numerous low-level vortices are initiated downwind of the Hoggar Mountains and progress toward the Atlantic coast on the northern path of African easterly waves (AEWs). These vortices occur mostly in July and August and more specifically when the northern position of the Saharan heat low (SHL) generates stronger and vertically expanded easterly winds over the Hoggar Mountains. At synoptic time scales, a composite analysis reveals that vortex initiation and westward motion are also statistically triggered by a reinforcement of these easterly winds by a wide and persistent high pressure anomaly developing around the Strait of Gibraltar and by a weak wave trough approaching from the east. The vortices are generated in the lee of the Hoggar, about 1000 km west of this approaching trough, and intensify rapidly. The evolution of the vortex perturbation is afterward comparable with the known evolution of the AEWs of the northern path and suggest a growth due to dry barotropic and baroclinic processes induced in particular by the strong cyclonic shear between the reinforced easterly winds and the monsoon flow. These results show that vortex genesis promoted by changes in orographic forcing due to the strengthening of easterly winds over the Hoggar Mountains is a source of intensification of the northern path of AEWs in July and August. These results also provide a possible mechanism to explain the role of the SHL and of particular midlatitude intraseasonal disturbances on the intensity of these waves.

Piptatherum fumeauxii (Poaceae), a New Species from Algeria

Piptatherum fumeauxii F.M. Vázquez, Chamboul. & C. Chatel. sp. nova (Poaceae) is described from the Hoggar Mountains in central Sahara, Algeria. It morphologically resembles P. coerulescens and P. holciforme var. longiglume, but differs from them by the narrow panicles, shorter spikelets and smaller floral parts. The presence of P. holciforme in Libya is confirmed, while it is excluded from the flora of Morocco. Lecto-types are designated for the names Milium coerulescens Desf. and P. holciforme subsp. longiglume Hausskn., and the latter is recognized as P. holciforme subsp. longiglume (Hausskn.) Freitag ex F.M. Vázquez & F. Márquez comb. et stat. nov.

Chenopodium hoggarense (Amaranthaceae), a new species from Algeria and Chad

Chenopodium hoggarense Uotila & C. Chatel., a new species of the family Amaranthaceae s.l. (Chenopodiaceae s.str.) from the Hoggar and Tibesti mountains of the Sahara, in Algeria and Chad, is described and illustrated. The species was found in quantities from the Hoggar (Ahaggar) mountains in 2019. It had been observed there earlier several times, but it was confused with C. vulvaria L. because of its similar smell and dense cover of vesicular hairs. However, it differs from C. vulvaria in growth habit, leaf shape and flower characters. Its relationships to and the identity of C. vulvaria var. incisum Maire are discussed and var. incisum is lectotypified. Chenopodium hoggarense is known only from the isolated Hoggar and Tibesti mountains. Citation: Chatelain C., Uotila P., Benhouhou S., Mombrial F., Mesbah M., Baa S. & Benghanem A. N. 2022: Chenopodium hoggarense (Amaranthaceae), a new species from Algeria and Chad. – Willdenowia 52: 75–81. Version of record first published online on 14 March 2022 ahead of inclusion in April 2022 issue.

Influence of Orography Upon Summertime Low‐Level Jet Dust Emission in the Central and Western Sahara

AbstractLow‐level jets (LLJs) drive frequent emission of mineral dust in the central and western Sahara in boreal summer. A major hotspot for this process is central Algeria, northern Mali and Mauritania, through which blow the dry near‐surface northeasterly Harmattan winds, with a peak in dust emission around the low‐lying Tidihelt region. North African orography is thought to contribute to the strength of the LLJ over the Bodele dust source in Chad, but its influence on erosivity over summertime source regions remains unquantified. In this paper, the contribution of central Saharan orography to the strength of Harmattan LLJs and associated dust emission frequency is tested. An idealized simulation with flattened Hoggar mountains is compared with a control using the Met Office Unified Model at 12 km horizontal resolution. In the absence of the Hoggar mountains, dust emission frequency estimated using an empirical relationship with surface wind speeds is found to decline across the entire northeasterly “LLJ alley,” including by 31% in the Tidihelt where composited jet surface winds drop from 9.0 to 7.3 m s−1 under a more easterly regime. The mountains are linked to a low‐level leeward geopotential height perturbation, with a northern limb reinforcing northeasterlies through the Tidihelt. Dome‐shaped elevated heating situated over the Hoggar mountains explains the difference between the simulated wind fields in the two experiments. These findings suggest that central Saharan orography plays an important role in sustaining erosive dusty conditions during boreal summer.

Iberian inscriptions in Sahara Desert rocks (Ti-m Missaou, Ahaggar Mts. area, Algeria): first evidence of incise Iberian rock scripts in continental North Africa

In the present paper, we show Iberian or Iberian-Guanche scripts found in the Middle of Sahara Desert, Ti-m Missaou (Tim Missao, Tim Missaw), 270 km SouthWest of Tamanrasset on Ahaggar or Hoggar Mountains (Mts.) area (Algeria). More Iberian scripts may be earthed beneath Sahara Desert sands or have been neglected by observers. We also put forward that Iberian semi-syllabary may have its origin in the Neolithic Saharo-Canarian Circle, the same as other Mediterranean, Atlantic and European lineal scripts (apart from Berber/Tuareg) like Etruscan, Runes, Old Italian languages, Minoan Lineal A, Sitovo and Gradeshnitsa (Bulgaria) writings (6,000 yearsBC) and others. In fact, Strabo wrote that Iberians had written language before since 6,000 BC. On the other hand, Sahara Desert was green and populated since before 5,000 years BC and we had proposed that most of Mediterranean culture, languages and writing, had a Saharan origin. Ti-m Missaou Sahara Iberian inscriptions, together with our previous and others researches on Canary Islands, further support this proposal, i.e.: rock scripts, Gimbutas-like Paleolithic figurines and unusual artifacts, like a lunisolar Egyptian-like calendar (“Cheeseboard/Quesera” at Lanzarote) carved in a Megalithic stone, do no support that Phoenicians and Romans carried Canarian ancient Guanche culture. Finally, a continuous lineal writing systems developing seems to have occurred during Paleolithic and Neolithic Epochs, which also harbor the related incise Lineal Megalithic Scripts that could have given rise to Iberian development and other lineal African, European and Mediterranean lineal language scripts. Our present new data is interpreted in the context of the Sahara people migration which occurred when hyperarid conditions started establishing about 6,000 years BC.
 Keywords: Iberian, Iberian-Guanche, Scripts, Canary Islands, Lanzarote, Fuerteventura, Prehistory, Saharo-Canarian Circle, Genetics, Megaliths, Iberia, Sahara, Atlantic, Mediterranean, Lineal Scripts, Neolithic, Tamanrasset, Hoggar, Ahaggar, Usko-Mediterranean,Etruscan, Tuareg, Berber, Lineal A.

Iberian inscriptions in Sahara Desert rocks (Ti-m Missaou, Ahaggar Mts. area, Algeria): first evidence of incise Iberian rock scripts in continental North Africa

In the present paper, we show Iberian or Iberian-Guanche scripts found in the Middle of Sahara Desert, Ti-m Missaou (Tim Missao, Tim Missaw), 270 km SouthWest of Tamanrasset on Ahaggar or Hoggar Mountains (Mts.) area (Algeria). More Iberian scripts may be earthed beneath Sahara Desert sands or have been neglected by observers. We also put forward that Iberian semi-syllabary may have its origin in the Neolithic Saharo-Canarian Circle, the same as other Mediterranean, Atlantic and European lineal scripts (apart from Berber/Tuareg) like Etruscan, Runes, Old Italian languages, Minoan Lineal A, Sitovo and Gradeshnitsa (Bulgaria) writings (6,000 yearsBC) and others. In fact, Strabo wrote that Iberians had written language before since 6,000 BC. On the other hand, Sahara Desert was green and populated since before 5,000 years BC and we had proposed that most of Mediterranean culture, languages and writing, had a Saharan origin. Ti-m Missaou Sahara Iberian inscriptions, together with our previous and others researches on Canary Islands, further support this proposal, i.e.: rock scripts, Gimbutas-like Paleolithic figurines and unusual artifacts, like a lunisolar Egyptian-like calendar (“Cheeseboard/Quesera” at Lanzarote) carved in a Megalithic stone, do no support that Phoenicians and Romans carried Canarian ancient Guanche culture. Finally, a continuous lineal writing systems developing seems to have occurred during Paleolithic and Neolithic Epochs, which also harbor the related incise Lineal Megalithic Scripts that could have given rise to Iberian development and other lineal African, European and Mediterranean lineal language scripts. Our present new data is interpreted in the context of the Sahara people migration which occurred when hyperarid conditions started establishing about 6,000 years BC.
 Keywords: Iberian, Iberian-Guanche, Scripts, Canary Islands, Lanzarote, Fuerteventura, Prehistory, Saharo-Canarian Circle, Genetics, Megaliths, Iberia, Sahara, Atlantic, Mediterranean, Lineal Scripts, Neolithic, Tamanrasset, Hoggar, Ahaggar, Usko-Mediterranean,Etruscan, Tuareg, Berber, Lineal A.

Molecular biogeography of the MediterraneanButhusspecies complex (Scorpiones: Buthidae) at its southern Palaearctic margin

AbstractNeogene orogenesis and climatic cycles strongly influenced inter- and intraspecific differentiation and variability of taxa. In this study, we focused on the southern margin of the western Palaearctic, known to be a geographically complex region. We performed mitochondrial DNA analyses of Buthus scorpions from the Moroccan Atlas Mountains, from the Hoggar Mountains in Algeria and from Tunisia, Iberia and Israel. Molecular species delimitation suggests the existence of ≥ 24 molecular operational taxonomic units. The data confirm complex differentiation patterns across the Atlas Mountains of Morocco, but structures in Iberia, Algeria and Tunisia have considerably lower complexity. This identifies the Atlas Mountain region as the most important differentiation centre of Buthus scorpions. Samples from the Hoggar Mountains (southern Algeria) cluster with those from the southernmost parts of Morocco in the middle and upper parts of the Draa Valley. This reinforces a recent connection of these regions. Samples from Israel are genetically similar to individuals from eastern Algeria and Tunisia. This suggests a widespread group across major parts of North Africa. Divergence time estimates indicate that differentiation in the genus began during the late Miocene, a period characterized by strong tectonic activities in this region. Further differentiation could be linked to subsequent climatic changes that have occurred since the end of the Miocene, with an increasing aridification of the Moroccan area. This also produced many microrefugia in the mountains of the area during the Pleistocene climatic fluctuations.

On Vortices Initiated over West Africa and Their Impact on North Atlantic Tropical Cyclones

AbstractUsing 38 years of the ERA-Interim dataset, an objective tracking approach is used to analyze the origin, characteristics, and cyclogenesis efficiency (CE) of synoptic-scale vortices initiated over West Africa and the Atlantic Ocean. Vortices initiated over the ocean at a given pressure level often result from a vertical expansion of a “primary” vortex track initiated earlier over West Africa. Low-level (850 hPa) primary vortices are initiated mainly in July near the Hoggar Mountains (24°N, 5°E), while midlevel (700 hPa) primary vortices are initiated mainly in August–September near the Guinea Highlands (10°N, 10°W). The CE of all these vortices is about 10% in July and 30% in August. The average CE is, however, smaller for low-level “Hoggar” vortices because they peak in July when the cyclogenesis potential index of the Atlantic Ocean is weak. Seasonal and interannual modulations of the cyclogenesis is related more to this index than to the number of vortices crossing the West African coast. Cyclogenesis is nearly equally distributed between the coast and 60°W, but the part of the cyclogenesis due to vortices initiated over West Africa decreases from 80% near the coast to about 30% at 60°W. The most probable delay between the vortex vertical expansion and cyclogenesis is 2 days, but it can be up to 10 days. This analysis also confirms previous results, such as the larger CE for vortices extending at low levels over the continent at 10°N, or the delayed and therefore west-shifted cyclogenesis of low-level “Hoggar” vortices.

Genetic variation in a colonization specialist, Simulium ruficorne (Diptera: Simuliidae), the world's most widely distributed black fly.

The ability of aquatic insects to colonize Earth’s most remote freshwater habitats, such as those of islands and deserts, is limited to select taxa. Among black flies, the premiere colonization specialist is Simulium ruficorne Macquart, the only species known from both the Afrotropical and Palearctic regions. We investigated the cytogenetics of S. ruficorne to gain insight into its wide geographic distribution and ability to colonize oceanic islands and deserts. On the basis of larval polytene chromosomes from 14 locations, we documented 17 novel and previously known chromosomal rearrangements and established five cytoforms (A1, A2, B, C, and D), of which probably four (A1/A2, B, C, and D) are distinct species and two (A1 and A2) represent sex-chromosome polymorphism involving a heteroband in the long arm of chromosome III. The chromosome restructuring phenomena associated with the five cytoforms are consistent with the trend in the Simuliidae that one and the same rearrangement can assume different functions in the various descendants of a common ancestor in which the rearrangement was polymorphic. The most widely distributed cytoforms are A1 and A2, which are found in North Africa, the Canary Islands, and Majorca. Simulium ruficorne, the only known black fly in the Hoggar Mountains of the central Sahara Desert, represents a cohesive population of cytoform A1 little differentiated from other North African populations of A1 and A2. Cytoform B inhabits the West African mainland, cytoform C is on Tenerife, and cytoform D is on Cape Verde. We suggest that dispersal and colonization specialists, such as S. ruficorne, are multivoltine inhabitants of temporary streams, and must relocate as their habitats deteriorate. Simulium ruficorne, therefore, should have adaptations that contribute to successful dispersal and colonization, perhaps largely physiological in nature, such as tolerance of high temperatures and droughts.

Phylogeography and ecological niche modeling unravel the evolutionary history of the African green toad,Bufotes boulengeri boulengeri(Amphibia: Bufonidae), through the Quaternary

Recent integration of ecological niche models in phylogeographic studies is improving our understanding of the processes structuring genetic variation across landscapes. Previous studies on the amphibian Bufotes boulengeri boulengeri uncovered a surprisingly weak intraspecific differentiation across the Maghreb region. We widely sampled this species from Morocco to Egypt and sequenced one nuclear and three mitochondrial (mtDNA) genes to determine the level of genetic variability across its geographic range. We evaluated these data with ecological niche modeling to reveal its evolutionary history in response to climate change during the Quaternary. Our results highlight some mtDNA phylogeographic structure within this species, with one haplogroup endemic to coastal Morocco, and one haplogroup widely distributed throughout North Africa. No or little genetic differentiation is observed between isolated populations from the Hoggar Mountains, the Sabha district and the islands of Kerkennah and Lampedusa, compared to others populations. This can be explained by the expansion of the distribution range of B. b. boulengeri during glacial periods. This might have facilitated the species’ dispersal and subsequent gene flow between most North African localities.

Ksour of the SAHARA Desert as A Great Lesson of Sustainable Urban Design in Hot Desert Oases

Despite the severity of the SAHARA Desert from many aspects, the man was able to confront it, and to build great human  settlements distributed in different areas as the REG of Mzab Valley, the ERG of Righ Valley, Hoggar Mountains ... And many others points to human life.These Settlements called SAHARAN Ksour, which become today a valuable architectural and urban heritage. This paper presents a thorough study on SAHARAN Ksour from an environmental point of view, so we focused on its adaptation with the different environmental elements, and speaks about the most important components of architectural and urban design as: The internalization concept. Half-covered street system. Twisted street design. And the use of the palm grove as a climatic component of urban and architectural design. And how to deal with environmental variables such as warm winds (Sirocco), sandy spring wind, high temperatureand the seriously low humidity, all these elements, components and relations are presented in this paper in manyexamples of Ksour situated in Algerian SAHARA. This paper is a lesson between environmental components and SAHARA desert urban heritage, which we aim to give prominence to the ability of the past SAHARAN human settlements to challenge the desert at the time where present ones can't challenge it, all this to find a formula for the future SAHARA desert sustainable architectural and urban design.

Derivation of an observation-based map of North African dust emission

Changes in the emission, transport and deposition of aeolian dust have profound effects on regional climate, so that characterizing the lifecycle of dust in observations and improving the representation of dust in global climate models is necessary. A fundamental aspect of characterizing the dust cycle is quantifying surface dust fluxes, yet no spatially explicit estimates of this flux exist for the World’s major source regions. Here we present a novel technique for creating a map of the annual mean emitted dust flux for North Africa based on retrievals of dust storm frequency from the Meteosat Second Generation Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the relationship between dust storm frequency and emitted mass flux derived from the output of five models that simulate dust. Our results suggest that 64 (±16)% of all dust emitted from North Africa is from the Bodele depression, and that 13 (±3)% of the North African dust flux is from a depression lying in the lee of the Air and Hoggar Mountains, making this area the second most important region of emission within North Africa.

A three-year time series of mineral dust deposits on the West African margin: Sedimentological and geochemical signatures and implications for interpretation of marine paleo-dust records

Mineral dust deposits in the Northeastern Tropical Atlantic Ocean (NETAO) are an important contribution for reconstructing paleoenvironments and paleoclimates of West Africa. However, the interpretation of the changes in the sedimentological and geochemical characteristics of the dust deposits recorded in the marine sediments from the NETAO remains incomplete. In order to improve our understanding of dust proxies, in particular its mineralogical and geochemical provenance tracers, present-day dust deposition has been monitored at Mbour (∼80km south of Dakar) on the Senegalese margin. Here we report a multi-proxy investigation of a unique three-year continuous time series of mineral dust deposits collected at a weekly (or better) temporal resolution over the March 2006–March 2009 period. Mass deposition flux and mean modal grain size display marked but reverse seasonal features, with higher flux during the winter/spring seasons and coarser grain size mode in summer when flux is minimal, reflecting contrasting transport patterns throughout the year. Similarly, clay mineralogy, the illite/kaolinite ratio in particular, shows seasonal fluctuations, manifesting the latitudinal displacement of the contributing domains of provenance in response to the seasonal migration of the ITCZ position and the associated wind systems. Our three-year record also reveals the occurrence of major deposition events superimposed on the seasonal pattern, generally during the winter/spring dry seasons and most frequently during the month of March. Our study shows that these major events, which contribute a large fraction of the total annual deposition flux, all originate from the western Sahara–Sahel (a major area of emission in the region beside the Bodele Depression, stretching from the Mauritanian and Western Saharan coasts to the Hoggar Mountains). Combined with air mass tri-dimensional back-trajectories and satellite images, the mineralogical and Sr–Nd isotopic compositions of these large dust events enable us to identify several mineralogically and geochemically distinct provenance sectors within this vast western area. Unlike the background dust deposits, the 87Sr/86Sr and the εNd isotopic signatures of the major dry events closely match that of the NETAO Late Holocene sediments, supporting the hypothesis that these events account for most of the aeolian terrigenous supply reaching the ocean floor. Although this database needs to be expanded, our results already provide useful constraints for the interpretation of the dust proxies' variations in marine sedimentary archives off Mauritania/Senegal in terms of changes in wind regimes and aridity over West Africa.

Ice nucleation efficiency of clay minerals in the immersion mode

Abstract. Emulsion and bulk freezing experiments were performed to investigate immersion ice nucleation on clay minerals in pure water, using various kaolinites, montmorillonites, illites as well as natural dust from the Hoggar Mountains in the Saharan region. Differential scanning calorimeter measurements were performed on three different kaolinites (KGa-1b, KGa-2 and K-SA), two illites (Illite NX and Illite SE) and four natural and acid-treated montmorillonites (SWy-2, STx-1b, KSF and K-10). The emulsion experiments provide information on the average freezing behaviour characterized by the average nucleation sites. These experiments revealed one to sometimes two distinct heterogeneous freezing peaks, which suggest the presence of a low number of qualitatively distinct average nucleation site classes. We refer to the peak at the lowest temperature as "standard peak" and to the one occurring in only some clay mineral types at higher temperatures as "special peak". Conversely, freezing in bulk samples is not initiated by the average nucleation sites, but by a very low number of "best sites". The kaolinites and montmorillonites showed quite narrow standard peaks with onset temperatures 238 K

The effect of orography and surface albedo on stratification in the summertime Saharan boundary layer: Dynamics and implications for dust transport

Observations have shown that there are significant day‐to‐day variations in the stratification of the Saharan boundary layer, which is a control on regional dust transport and mixing. It has been suggested that the Hoggar Mountains, in the east part of the Sahara desert, act as an elevated heat source that injects air out of the convective boundary layer, induces subsidence, and inhibits the growth of the daytime convective boundary layer (CBL) over the western (remote) part of the Sahara. Here model experiments are performed for three case study periods: control cases and runs with the surface albedo and orographic variations in the Hoggar region removed. It is shown that plumes of hot air over the mountains can inject hot air (which may be dust laden) through the Saharan residual layer to altitudes of 8 km. The mountains and, to a lesser extent, the patches of low surface albedo produce a deeper and warmer CBL up to 400 km west of the main peaks. The model simulations also provide evidence that the mountains inhibit the daytime growth of the remote convective boundary layer, as postulated in earlier observational papers. However, the mechanism for this remote influence on the boundary layer is not subsidence induced by the mountains. Instead, the mountains act as an obstacle to the larger‐scale northeasterly flow and divert cooler air to the west and east of the mountain range. This cools the remote boundary layer and therefore reduces the depth of the daytime CBL.

Disjunctions in the Diptera (Insecta) fauna of the Mediterranean Province and southern Africa and a discussion of biogeographical considerations

This paper explores disjunctions in the Diptera fauna of the Mediterranean Province and southern Africa, drawing from eight families of Diptera, the more ancient Psychodidae and Vermileonidae, and the more recent Acroceridae, Asilidae, Bombyliidae, Dolichopodidae, Pipunculidae and Sciomyzidae. Information from recent published revisions is geo-referenced and plotted onto maps using GIS software. These distribution patterns are interpreted and probable means and routes of dispersal between the two regions are discussed. The concept of an Afrotropical sub-Saharan boundary is outlined and it is argued that although the vast, arid and virtually abiotic Sahara acts as a barrier to dispersal today, relict floral and faunal populations of Mediterranean provincial origin still occur on the Hoggar and Tibesti Mountains of the central Sahara, indicating that the aridification of the Sahara is a very recent event. The presence of extensive palaeolakes formerly covering ca 10% of the present-day Sahara is regarded as evidence in support of this hypothesis. These lakes and their associated catchments, situated in basins between the central Saharan mountains, could clearly have acted as a humid route of dispersal as recently as 4000 BP, when these lakes began to recede, and this route is here regarded as a “central high Africa corridor”; a filter-bridge between the Mediterranean Province and southern Africa. Examples of Mediterranean provincial species of Ephydridae and the muscid genus Lispe Latreille, 1796, occurring as far south as the Aïr Massif in northern Niger are cited as examples of relict montane Diptera of Mediterranean provincial origin in the southern Hoggar Mountains; these groups being associated with the margins of standing water. Balinsky's (1962) concept of an “arid corridor” is also re-examined, using examples from the larger, less mobile Diptera, and it is concluded that such a pattern may not be the result of aridity, but represent an “eastern high Africa corridor”, broadly corresponding to the “African Superswell”. Other perceived distribution pathways between the Holarctic and Afrotropical Regions are mapped. Anemochore dispersal is considered, and the extent of the Afrotropical Region is discussed. Mediterranean tectonic evolution on both a globe of constant size and on a smaller Jurassic globe is also considered. It is concluded that if all the transitional zones between the zoogeographical regions are to be given more-or-less equivalent treatment, we must avoid setting boundaries based on earlier faunal distributions. For this reason the current boundary between the Palaearctic and Afrotropical Regions, arbitrary as it is, should be retained, despite evidence suggesting recent continuity between sub-Saharan Africa, North Africa and the Arabian Peninsula, corresponding broadly to the African and Arabian lithospheric plates.

Phylogeography of the false smooth snakes, Macroprotodon (Serpentes, Colubridae): mitochondrial DNA sequences show European populations arrived recently from Northwest Africa

Mitochondrial DNA (1075 bp: cytochrome b, 300 bp; 12S rRNA, 393 bp; and 16S rRNA, 382 bp) corroborates the monophyly of the genus Macroprotodon and of the species M. mauritanicus, M. abubakeri, and M. brevis. The subspecies M. brevis ibericus is also monophyletic. The mtDNA tree presented here indicates that M. cucullatus consists of at least two separate units and may possibly represent a primitive morphology rather than a species in its own right. However, this hypothesis is tentative since it is only reflects the history of a single evolutionary unit (mtDNA). A definitive understanding of the evolution of M. cucullatus will not be possible until informative nuclear markers are added to the mitochondrial data. Macroprotodon appears to have originated in the Maghreb region of NW Africa and speciated there around 4–5.5 million years ago around the end of the Miocene period, after which its three main lineages may each have expanded north into more mesic conditions. The group also spread eastwards into coastal areas of Libya quite recently and on to Egypt and Israel. Later still, M. b. ibericus from extreme north Morocco reached the Iberian Peninsula, and M. mauritanicus from Tunisia or Algeria colonised the Balearic Islands of Menorca and Mallorca. Both these range extensions may result from very recent natural colonisations or even from accidental human introduction. Recency of origin of Iberian and Balearic populations is indicated by uniformity of their mtDNA even across large distances, and its great similarity to that of populations in source regions. Isolated populations assigned to M. cucullatus in the Hoggar mountains (southern Algeria) and Western Sahara are probably relicts from quite recent periods of climatic amelioration in the North African desert.

Lee vorticity Production by Large-Scale Tropical Mountain Ranges. Part II: A Mechanism for the Production of African Waves

Abstract A mechanism that acts to produce vorticity in the lee of large-scale mountain ranges embedded in an easterly flow in a stably stratified rotating atmosphere is investigated as it applies to the production of westward-propagating African waves. Three-dimensional numerical simulations of a dry, adiabatic flow using the PSU/NCAR MM4 model show that the Hoggar and Atlas Mountains of west-central Africa block low-level easterly flow, resulting in a barotropically unstable jet that is associated with the continuous production of lee vortices, which separate from the mountain and propagate downstream. The wavelength of the disturbances is roughly 1600 km, and they propagate to the west with a period of about 2.5 days. These characteristics correspond to those of observed waves in the Africa-Atlantic region. It is also shown that flow interaction with the topography of north-central Africa results in a midtropospheric easterly jet having a maximum wind speed near 10 ms−1 between 15° and 20°N, 0° and 10°E...