Systematics, biogeography and evolution of selected widespread reptile genera from the arid areas of North Africa and Arabia

Abstract

The arid areas of North Africa and Arabia cover a surface of more than 13 million square kilometers and are characterized by their extreme temperatures, diversity of desert habitats and well-adapted flora and fauna. The study of the evolution of their biota sheds light on the diversification processes in some of the world’s harshest environments and contributes to our knowledge on large-scale biogeographic patterns and processes. The general aim of this dissertation is to investigate the evolution of the biota of the arid areas of North Africa and Arabia, through the study of the systematics and biogeography of two representative reptile groups, Stenodactylus and Ptyodactylus. The geckos of these two genera are among the most common faunal elements of the arid North African and Arabian environments, yet they are very distinct with regard to their morphology, ecology and patterns of species divergence. On the one hand, the naked toe Stenodactylus species are relatively divergent morphologically and have conquered different arid and hyper-arid habitats across plains or dunes. On the other hand, Ptyodactylus geckos are fairly conserved morphologically across their entire range and are very well adapted to a common type of structural habitat characterized by the rocky substrate. The results presented herein provide a thorough insight into their phylogenetic relationships, review and update their taxonomy, explore their historical biogeography and, altogether, assemble a broader image of diversity patterns within a temporal framework for the arid North Africa and Arabia.

Highlighting the most relevant results, in this dissertation an unprecedentedly large set of samples from North Africa, the Sahel and Arabia was compiled for the two selected groups of study: 249 samples of Stenodactylus from 150 localities and 382 samples of Ptyodactylus from 221 localities. Regarding molecular data, 770 DNA sequences of five different markers were newly produced for the former genus, and 1443 of six different markers for the latter. Stenodactylus originated in Arabia in the Late Oligocene. The Arabian Clade B, including five species, and the mainly African Clade C, with the same number of species, split approximately 22 Ma ago, coinciding with the opening of the Red Sea. Diversification within several clades in the phylogeny occurred during the Late Miocene, a time when a general increase in aridification initiated. Based on mitochondrial and nuclear molecular data, as well as morphological characters, a new species of Stenodactylus is described. Stenodactylus sharqiyahensis sp. nov. is shown to be endemic to the sand desert of Al Sharqiyah, in northeastern Oman. Nomenclatural actions undertaken for the stability of the nomina of North African species of Stenodactylus include the designation of a lectotype for the nomen Stenodactylus guttatus which places it under the synonymy of P. hasselquistii, ensuring continuity of the prevailing usage of S. petrii, and the application to the International Commission of Zoological Nomenclature to accept a new name-bearing type for S. sthenodactylus, in order to maintain its prevailing usage. Regarding Ptyodactylus, its broad sampling includes numerous new records for some of the species, and especially for the P. hasselquistii species complex, an important extension of its known distribution range both in northeastern Africa and Arabia. All the formerly known and newly-delimited species are shown to be mostly allopatric, except some known cases where activity patterns are adjusted to avoid competition. This is hypothesized to relate to their preference for the same type of structural habitat, conditioning their apparently conserved morphology. The onset of the diversification in the genus Ptyodactylus is estimated to have taken place in the Late Oligocene. In the northeastern African and Arabian clades A, B and C, diversification started during the Late Miocene, approximately 9.5-12 Ma ago, posterior to that in the western African P. togoensis and P. oudrii. The molecular data show that many species have high levels of genetic variability. Ptyodactylus ragazzii presents two clades in the phylogeny, from East and West Africa respectively, and given that topological tests reject their sister relationship, the available name P. togoensis is assigned to the West African populations. Multilocus coalescence-based analyses with the use of GMYC and BPP methodologies result in the delimitation of 17 putative species in the P. hasselquistii species complex. These species are grouped in two major clades: Clade A, with nine species, is distributed across northeastern Africa and a large part of north, central and eastern Arabian Peninsula, and Clade B, with eight species, is restricted to southern Arabia.

Les zones àrides del Nord d'Àfrica i d'Aràbia s'estenen per diversos milions de kilòmetres quadrats i l'estudi en aquesta àrea dels patrons de biodiversitat a gran escala, es veu condicionat de forma essencial per la dificultat d'obtenir un mostreig complet, per l'escassa informació de la seva biota i per la complexitat dels processos que han generat la biodiversitat actualment existent. En el marc limitat d'una tesi doctoral, i considerant les premisses anteriorment descrites, s'han seleccionat dos gèneres de rèptils àmpliament distribuïts en aquestes àrees, el gènere Stenodactylus i el Ptyodactylus. Ambdós gèneres formen part dels elements més comuns de la fauna del Nord d'Àfrica i d'Aràbia, malgrat presentar importants diferències pel que fa a la seva morfologia, ecologia i patrons de divergència. Per un costat, les espècies dels dragons del gènere Stenodactylus són relativament divergents entre elles respecte a la morfologia, i han conquistat diferents ambients àrids i hiperàrids, incloent-hi alguns dels entorns més hostils dels deserts. Per altra banda, els dragons del gènere Ptyodactylus són més aviat conservats pel que fa a la morfologia, sempre presentant els característics coixinets triangulars dividits en múltiples làmines en les seves potes, i estan ben adaptats als substrats rocosos, que constitueixen el seu hàbitat estructural. Els resultats aquí presentats aporten un coneixement profund en les seves relacions filogenètiques, es revisa i s'actualitza la seva taxonomia, s'explora la seva biogeografia històrica, i en conjunt, es dona una imatge general dels patrons de diversitat dins d'un marc temporal pels ambients àrids del Nord d'Àfrica i d'Aràbia.