While some areas of the world are renowned for their high diversity of life, such as the tropics, others, such as deserts, are generally perceived as deprived of diversity. This is, however, very far from the truth.
Above: The Saudi Dwarf Gecko, Tropiocolotes wolfgangboehmei, whose phylogenetic position was unknown until our study. Picture by Al Faqih Ali Salim.
Biodiversity is not distributed evenly across the world and understanding the factors that generate common patterns is of fundamental importance to the study of evolutionary biology. While some areas of the world are renowned for their high diversity of life, such as the tropics, others, such as deserts, are generally perceived as deprived of diversity. This is, however, very far from the truth. Deserts all over the world are abundant with species that are perfectly adapted for their harsh environmental conditions.
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Šmíd J, Sindaco R, Shobrak M, Busais S, Tamar K, Aghová T, Simó-Riudalbas M, Tarroso P, Geniez P, Crochet P-A, Els J, Burriel-Carranza B, Tejero-Cicuéndez H, Carranza S (2021). Diversity patterns and evolutionary history of Arabian squamates. Journal of Biogeography, 48: 1183–1199.https://doi.org/10.1111/jbi.14070
Deserts tend to be very difficult to access for researchers and Arabia is no exception to this rule. Although we have been studying various aspects of the diversity of Arabian squamates for more than fifteen years now, from conducting exhaustive field trips, collecting new genetic, environmental, and distribution data, revising the taxonomy and systematics of many groups, to continuously discovering new species along the way, we felt that a broader picture was still missing.
To understand the general patterns, evolutionary history, and drivers of the diversity of Arabian squamates we compiled all available distribution records to derive range maps for all the species, and we reconstructed their evolutionary relationships. This included species that had been known only from their taxonomic descriptions (like the Saudi dwarf gecko, Tropiocolotes wolfgangboehmei, depicted here) or species that have not yet been formally described. This allowed us for the first time to produce a detailed map of squamate species richness of the Arabian Peninsula. By including the evolutionary component, we were able to identify main hotspots where long evolutionary history is concentrated. We found that the mountains that rim the peninsula support rich and unique communities that are dominated by local radiations. In particular, the Asir Mountains of southwestern Arabia, the Dhofar Mountains of extreme eastern Yemen and southern Oman, and the Hajar Mountains of northern Oman and UAE show unprecedented levels of squamate endemism and phylogenetic endemism. The mountains can thus be viewed as diversification hubs that generate new species and maintain their high diversity. The deserts in the interior of the Arabian Peninsula are generally inhabited by widely distributed generalist species.
In suitable habitats, some lizard species can attain high local population densities, like the endemic Sharqiyah Toad-headed Agama, Phrynocephalus sakoi, from the Sharqiyah Sands, Oman. Picture by Jiri Smid.
How can the mountains harbor so many species when they cover only a minor part of Arabia in sharp contrast to the vast inland deserts? The key variable seems to be topographic complexity or, in other words, heterogeneity of different environments. Heterogeneous environments provide a large number of available habitat types and thus numerous opportunities for niche partitioning, population isolation, allopatric speciation, and ultimately the coexistence of multiple divergent lineages.
Our study not only sheds light on the processes that have helped to generate and maintain the diverse and unique fauna of Arabian squamates, but it may also be used to direct future conservation efforts that would focus on the preservation of the evolutionary history of the Arabian fauna.
Jiri Smid; Associated Researcher; Department of Zoology, Faculty of Science, Charles University, Prague, Czech Republic
Mohammed Shobrak; Professor; Department of Biology, Faculty of Science, Taif University, PO Box 11099, Taif 21944, Saudi Arabia
Salem Busais; Associated Professor; Department of Biology, Faculty of Education, University of Aden, Aden, Yemen
Karin Tamar; Postdoc; Institute of Evolutionary Biology (CSIC-UPF), Barcelona, Spain
Johannes Els; Head of Department; Herpetology and Freshwater Fishes, Environment and Protected Areas Authority, Sharjah, UAE
Bernat Burriel-Carranza; PhD student; Institute of Evolutionary Biology (CSIC-UPF), Barcelona, Spain
Salvador Carranza; Director; Institute of Evolutionary Biology (CSIC-UPF), Barcelona, Spain
Jiri Smid: https://scholar.google.cz/citations?user=vsAjzyYAAAAJ&hl=en
Mohammed Shobrak: https://scholar.google.com/citations?user=-SsOYv0AAAAJ&hl=en; @mshobrak; https://www.facebook.com/mshobrak
Salem Busais: http://www.arbiodiversity.academia-srt.net/; https://scholar.google.com/citations?user=yv4t5B0AAAAJ&hl=en; @SBusais
Karin Tamar: https://scholar.google.co.il/citations?user=j_Nx_5oAAAAJ&hl=en&oi=ao
Johannes Els: https://scholar.google.cz/citations?user=h3sJUiYAAAAJ&hl=en&oi=ao
Bernat Burriel-Carranza: https://scholar.google.es/citations?user=k1QIuk4AAAAJ&hl=es
Salvador Carranza: http://molevol.cmima.csic.es/carranza/index.html; https://scholar.google.es/citations?hl=en&user=AOP1VxMAAAAJ&view_op=list_works&sortby=pubdate