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The Hajar Mountain range is the highest in eastern Arabia, forming a spectacular isolated wall of rock that rises dramatically from the sea below. It runs northwest to southeast in a 650 km continuous arc parallel to the Oman and UAE coastline along the Gulf of Oman, from the Musandam Peninsula to Ras Al Hadd. This impressive massif is flanked by the sea to the East and by very large gravel and sand deserts to the West and South. Cut by deep wadis, these arid mountains have a complex topography and can be divided into three distinct blocks; Western Hajars, Jebel Akhdar and Eastern Hajars; separated by some topographical discontinuities. With a maximum elevation of 3,009 m, Jebel Shams in the Jebel Akhdar massif is the highest peak, although several peaks above 2,000 m also occur in the Eastern and Western Hajars. The Hajar Mountains originated about 30 Mya due to the tectonic motions that resulted in the opening of the Red Sea and the Gulf of Aden but final uplift occurred approximately 4–6 Mya. The Hajar Mountains are usually referred to as a mountain desert for its arid conditions but it is actually one of the most climatically variable areas in southeastern Arabia. Owing to its geological origin, high elevations, very deep canyons and geographic isolation from other mountains, high levels of species richness and endemicity are recorded in several animal and plant groups, making the Hajar Mountains a focal point of conservation in Arabia. To date, 28 species of reptiles and two amphibians inhabit the Hajar Mountains and this number is likely to increase in the next few years as a result of ongoing research. Of these species, 19 are endemic to the massif, which means that they do not live anywhere else in the world, highlighting the importance of the Hajar Mountains as a hotspot of reptile diversity and endemicity., Scientific research has been funded by grants CGL2015-70390-P and PGC2018-098290-B-I00 funded by MCIN/AEI /10.13039/501100011033/ and by FEDER, a way to make Europe, and by project 22412027 from the Ministry of Environment and Climate Affairs, Oman to S. Carranza. B. Burriel-Carranza is supported by an FPU grant (FPU18/04742) (MCIU, Spain).

The lacertid lizards of the genus Mesalina inhabit the arid regions of the Old World, from North Africa to NW India. Of the 19 recognized species within the genus, eleven occur in Arabia. In this study, we explore the genetic variability and phylogeographic patterns of the less studied M. adramitana group from southern Arabia and the Socotra Archipelago within the phylogenetic and biogeographic context of the entire genus. Our unprecedented sampling extends the distribution ranges of most Mesalina species and, for the first time, sequences of M. ayunensis are included in a phylogenetic analysis. We perform analyses of concatenated multilocus datasets and species trees, conduct species delimitation analyses, and estimate divergence times within a biogeographic framework. Additionally, we inferred the environmental suitability and identified dispersal corridors through which gene flow is enabled within M. adramitana. Our results show that the Socotra Archipelago was colonized approximately 7 Mya by a single oversea colonization from mainland Arabia. Then, an intra-archipelago dispersal event that occurred approximately 5 Mya resulted in the speciation between M. balfouri, endemic to Socotra, Samha and Darsa Islands, and M. kuri, endemic to Abd al Kuri Island. Similar to previous studies, we uncovered high levels of genetic diversity within the M. adramitana species-group, with two highly divergent lineages of M. adramitana living in allopatry and adapted to locally specific climatic conditions that necessitate further investigation., All efforts were made to minimize animal suffering. All collecting and export permits were issued by the Nature Conservation Department of the Ministry of Environment and Climate Affairs, Oman (Refs: 08/2005; 16/2008; 38/2010; 12/2011; 13/2013; 21/2013; 37/2014; 31/2016). This work was supported by the Ministerio de Economía y Competitividad, Spain (co-funded by FEDER) under grant numbers CGL2012-36970 and CGL2015-70390-P; Ministry of Environment and Climate Affairs under Grant number 22412027; Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya under grant number 2017-SGR-00991. MSR was funded by an FPI grant from the Ministerio de Economía y Competitividad, Spain (BES-2013-064248). JS was funded by the Czech Science Foundation (GACR, project number 18-15286Y) and the Ministry of Culture of the Czech Republic (DKRVO 2019–2023/6.VII.a, 00023272).

Large parts of the Sahara Desert and Arabia are covered by sand seas and sand dunes, which are inhabited by specialized animal communities. For example, many lizards have developed adaptations to life in loose sand, including sand-swimming behavior. The best-known sand swimmers of the Saharo-Arabia are the sandfish skinks (genus Scincus). Although there are currently only four Scincus species recognized, their phylogenetic relationships have not yet been addressed in detail. We use eight genetic markers (three mitochondrial, five nuclear) and a complete sampling of species to infer the relationships within the genus. We employ multiple phylogenetic approaches to reconstruct the evolutionary history of these skinks and to assess the level of reticulation at the onset of their radiation. Our results indicate the presence of five strongly supported species-level lineages, four represented by the currently recognized species and the fifth by S. scincus conirostris, which does not form a clade with S. scincus. Based on these results we elevate the Iranian and northern Arabian S. conirostris to the species level. The two Saharan species, S. albifasciatus and S. scincus, are sister in all analyses. Deeper relationships within the genus, however, remained largely unresolved despite the extensive genetic data set. This basal polytomy, together with the fact that we detected no sign of hybridization in the history of the genus, indicates that the diversification of the five Scincus species was rapid, burst-like, and not followed by secondary hybridization events. Divergence time estimations show a Middle Pliocene crown radiation of the genus (3.3 Mya). We hypothesize that the aridification of the Saharo-Arabia that began in the Late Miocene triggered the initial diversification of Scincus, and that the subsequent expansion of sand deserts enabled their dispersal over the large Saharan and Arabian range. We discuss the evolution of body form in sand swimming lizards and ponder how Scincus retained their fully limbed morphology despite being sand swimmers that are typically limbless., We are thankful to Taif University, Saudi Arabia, for support under Researcher Supporting project number (TURSP-2020/06). Field work in Oman was carried out in collaboration with the Nature Conservation Department of the Ministry of Environment and Climate Affairs, MECA (Refs: 08/2005; 16/2008; 38/2010; 12/2011; 13/2013; 21/2013; 37/2014; 31/2016). The work of JŠ was supported by the Czech Science Foundation (GACR, project number 18–15286Y) and the Ministry of Culture of the Czech Republic (DKRVO 2019–2023/6.VII.c, 00023272). MU was supported by Charles University (SVV 260571/2020). SC was supported by grant PGC2018-098290-B-I00 (MCIU/AEI/FEDER, UE).

Los reptiles son un grupo muy interesante de vertebrados terrestres. Han habitado nuestro planeta durante más de 250 millones de años y están adaptados a vivir en una amplia variedad de entornos. Hay más de 11.500 especies diferentes de reptiles en todo el mundo, divididas en tortugas, serpientes, lagartos y cocodrilos, que se caracterizan por su cubierta exterior escamosa. A pesar de su glorioso pasado, no siempre son bien apreciados por los humanos, especialmente en comparación con los mamíferos y las aves, ya que causan muchas muertes anualmente en todo el mundo. El Sultanato de Omán se considera el tercer país más grande de la Península Arábiga. Con sus vastos paisajes terrestres y marinos, alberga una de las biodiversidades más ricas de Arabia. Su fauna y vegetación únicas en las partes Norte y Central del país comparten especies con Irán y Pakistán, mientras que las del Sur presentan afinidades africanas. El Sultanato de Omán tiene aproximadamente el 50% del número total de especies de reptiles de la Península Arábiga, lo que lo convierte en uno de los países con mayor diversidad de reptiles de Arabia. A pesar de esta gran diversidad, todavía existen muchas lagunas en el conocimiento de la historia de vida, el tamaño de la población y la distribución real de los reptiles de Omán. Además de eso, se espera que el cambio climático cause más estrés por el incremento del calor, cambiando los hábitats naturales de muchas especies de reptiles y haciendo muy difícil predecir cómo estos se verán afectados., Scientific research in Oman has been funded by grants CGL2015-70390-P (MINECO/FEDER, UE) Spain, PGC2018-098290-B-I00 (MCIU/AEI/FEDER, UE) Spain, and by project 22412027 from the Ministry of Environment and Climate Affairs, Oman to S. Carranza. B. Burriel-Carranza is supported by an FPU grant (FPU18/04742) (MCIU, Spain).

Pous, Philip de et al., 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)., This work was supported by the project ‘Field study for the conservation of reptiles in Oman’ funded by the Ministry of Environment and Climate Affairs, Oman (Ref: 22412027), and grant CGL2012-36970 from the Ministerio de Economía y Competitividad, Spain (cofunded by FEDER). PdP is funded by a FI-DGR grant from the Generalitat de Catalunya, Spain (2014FI_B2 00197). The work of JŠ was financially supported by Ministry of Culture of the Czech Republic (DKRVO 2015/15, National Museum, 00023272). LM is funded by Fundação para a Ciência e Tecnologia (FCT) through a PhD grant (SFRH/BD/89820/2012) financed by Programa Operacional Potencial Humano (POPH) – Quadro de Referência Estratégico Nacional (QREN) from the European Social Fund and Portuguese Ministério da Educação e Ciência. MSR is funded by a FPI grant from the Ministerio de Economía y Competitividad, Spain (BES-2013-064248).

[Background] The 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., [Methods] A 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., [Results] The 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., [Discussion] Using 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., This work was funded by grants CGL2012-36970, CGL2015-70390-P from the Ministerio de Economía y Competitividad, Spain (cofunded by FEDER), the project ‘Field study for the conservation of reptiles in Oman’, Ministry of Environment and Climate Affairs, Oman (Ref: 22412027) and grant 2014-SGR-1532 from the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya. MSR is funded by a FPI grant from the Ministerio de Economía y Competitividad, Spain (BES-2013-064248).