Microendemicity in the northern Hajar Mountains of Oman and the United Arab Emirates with the description of two new species of geckos of the genusAsaccus(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 genusAsaccusrepresent the genus with the highest number of endemic species in the Hajar Mountains. Recent taxonomic studies on the Zagros populations ofAsaccushave 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 asAsaccus caudivolvulus(including specimens of the two new species described herein), six otherAsaccusspecies from the Hajar and the Zagros Mountains and two representatives of the genusHaemodraconwere sequenced for up to 2,311 base pairs including the mitochondrial12Sandcytband the nuclearc-mos,MC1RandACM4genes. 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 asAsaccus caudivolvulusfrom 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 asAsaccus caudivolvulusis, in fact, an assemblage of three different species that started diversifying during the Mid-Miocene. The molecular phylogenies consistently recovered the Hajar endemicA. montanusas sister taxon to all the otherAsaccusspecies included in the analyses, rendering the Arabian species ofAsaccuspolyphyletic.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 caudivolvulusis 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.