Abstract
BackgroundThe colubrid snakes of the genus Rhynchocalamus are seldom studied and knowledge of their ecology and life history is scarce. Three species of Rhynchocalamus are currently recognized, R. satunini (from Turkey eastwards to Iran), R. arabicus (Yemen and Oman), and R. melanocephalus (from the Sinai Peninsula northwards to Turkey). All are slender, secretive, mainly nocturnal and rare fossorial snakes. This comprehensive study is the first to sample all known Rhynchocalamus species in order to review the intra-generic phylogenetic relationships and historical biogeography of the genus.MethodsWe revised the systematics of Rhynchocalamus using an integrative approach and evaluated its phylogeography. The phylogenetic position within the Colubridae and the phylogenetic relationships within the genus were inferred using 29 individuals belonging to the three known species, with additional sampling of two other closely-related genera, Muhtarophis and Lytorhynchus. We analysed three mitochondrial (12S, 16S, cytb) and one nuclear (c-mos) gene fragments. Phylogenetic trees were reconstructed using maximum likelihood and Bayesian inference methods; the latter method also used to provide the first time-calibrated molecular phylogeny of the genus. We generated a nuclear network and carried out a topology test and species delimitation analysis. Morphological comparisons were used to differentiate among species and to describe a new species from Israel. The studied material was comprised of 108 alcohol-preserved specimens, 15 photographs, and data from the literature for the examination of 17 mensural, 14 meristic, and two categorical characters.ResultsThe molecular results support Rhynchocalamus as monophyletic, and as having split from its sister genus Lytorhynchus during the Late Oligocene. The three recognized species of Rhynchocalamus comprise four independently evolving groups. The molecular results reveal that the genus began to diverge during the Middle Miocene. We revealed that the best-studied species, R. melanocephalus, is paraphyletic. A population, formally ascribed to this species, from the Negev Mountain area in southern Israel is phylogenetically closer to R. arabicus from Oman than to the northern populations of the species from Israel, Syria and Turkey. Herein we describe this population as a new species: Rhynchocalamus dayanae sp. nov.DiscussionWe identify four species within Rhynchocalamus: R. satunini, R. arabicus, R. melanocephalus, and R. dayanae sp. nov., the latter, to the best of our knowledge, is endemic to southern Israel. The onset of Rhynchocalamus diversification is very old and estimated to have occurred during the Middle Miocene, possibly originating in the Levant region. Radiation probably resulted from vicariance and dispersal events caused by continuous geological instability, sea-level fluctuations and climatic changes within the Levant region.
Highlights
Taxonomy today often relies on molecular data for further support and information
We explore the phylogenetic relationships within Rhynchocalamus by means of a broad sampling coupled with a morphological revision
In order to resolve the phylogenetic relationships within Rhynchocalamus, 29 individuals belonging to all three recognized species were used in the molecular study, including eight sequences from Avci et al (2015) and Šmíd et al (2015) that were retrieved from GenBank
Summary
Taxonomy today often relies on molecular data for further support and information. Such data are usually preferred over morphology for the reconstruction of evolutionary relationships among organisms (Hebert et al, 2003; Tautz et al, 2003; Blaxter, 2004; Vogler & Monaghan, 2007; Padial et al, 2010). Recent studies of Middle Eastern snakes have used molecular data to elucidate the inter- and intra-specific relationships among taxa, revealing high levels of genetic differentiation and cryptic diversity that do not accord with the current taxonomy. Such studies have provided insights into the historical biogeography of the taxa and the processes that triggered their diversification (e.g., Lenk et al, 2001; Utiger et al, 2002; Nagy et al, 2003; Nagy et al, 2004; Pook et al, 2009; Stümpel & Joger, 2009; Kornilios et al, 2013). Secretive, mainly nocturnal and rare fossorial snakes This comprehensive study is the first to sample all known Rhynchocalamus species in order to review the intra-generic phylogenetic relationships and historical biogeography of the genus. A population, formally ascribed to this species, from the Negev Mountain area in southern Israel is phylogenetically closer to R. arabicus from Oman than to the northern
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