Systematics of the Thirteen-scaled Green Snake Philothamnus carinatus (Squamata: Colubridae), with the description of a cryptic new species from Central and East Africa

ABSTRACT

Recent molecular phylogenies of African Green Snakes suggested the geographically widespread species Philothamnus carinatus includes at least two distinct lineages. We utilised an integrative taxonomic approach with morphological and genetic data to reconcile the taxonomic status of these cryptic lineages, including the recently described taxon P. brunneus from West Africa. We sequenced three mitochondrial (16S, cyt b and ND4) and two nuclear (c-mos and RAG1) genes from several Central African populations of P. carinatus and combined our data with other closely related species to infer a maximum likelihood phylogenetic tree with IQ-TREE. Our results are consistent with previous studies that showed P. cf. carinatus populations from Democratic Republic of the Congo (DRC) represent a cryptic lineage that is distinct from P. carinatus sensu stricto in Cameroon, Central African Republic, Equatorial Guinea (including Bioko Island), Gabon, eastern Nigeria, Republic of the Congo, and extreme western DRC. In our preferred tree, P. brunneus (limited to 16S molecular data) was recovered as a relatively long branch in a moderately supported clade with P. carinatus sensu stricto, whereas P. cf. carinatus populations from northern Angola, most of DRC, and East Africa (Burundi, Kenya, Rwanda, Tanzania and Uganda) were described as a new species. A possible hybrid population between south-eastern Cameroon and north-western DRC is consistent with an increasing body of evidence suggesting the Ubangi River might represent a hybrid zone area.

KEYWORDS:

• Congo River
• Ubangi River
• Congo Basin
• endemism

ACKNOWLEDGEMENTS

We thank Jonathan Brecko and Garin Cael for facilitating access to RMCA specimens; Bo Delling and Andrea Hennyey for NRM type specimens; Mark-O. Rödel and Franck Tillack for the ZMB type; Jennifer Sheridan and Stevie Kennedy-Gold for CM specimens; Kevin de Queiroz, Robert Wilson and Addison Wynn for USNM specimens; and Nicolas Vidal for MNHN specimens. Marius Burger, Kate Jackson, and J. Maximilian Dehling contributed photos of Philothamnus carinatus. Everett Madsen provided some photos of type specimens. Fieldwork by EG in DRC was funded by the Percy Sladen Memorial Fund, an IUCN/SSC Amphibian Specialist Group Seed Grant, K. Reed, M.D., research funds from the Department of Biology at Villanova University, two National Geographic Research and Exploration Grants (8556-08 and WW-R018-17), UTEP, and the US National Science Foundation (DEB-1145459). We are grateful to the Centre de Recherche en Sciences Naturelles for project support and permits (CRSN—LW1/28/BB/MM/BIR/050/07, an unnumbered permit from 2008, LWI/27/BBa/MUH.M/BBY/141/09, LWI/27/BBa/MUH.M/BBY/023/10, LWI/27/BBa/MUH.M/BBY/001/011, LWI/27/BBa/CIEL/BBY/003/012, LW1/27/BB/KB/BBY/60/2014, LWI/27/BBa/BBY/146/014), Institut Congolais pour la Conservation de la Nature for permits (ICCN—unnumbered permit by Provincial Director of ICCN, Équateur Province in Mbandaka in August 2013, 004/ICCN/PNKB/2013, 06/ICCN/PNKB/2014, 02/ICCN/PNKB/2015), and Institut Supérieur d’Ecologie Pour la Conservation de la Nature (ISEC, Katana—ISEC/DG/SGAC/04/2015, ISEC/DG/SGAC/04/29/2016). VG would like to thank Ernest Vunan for logistical support and Oldřich Kopecký for assistance in the field in Cameroon, where the material was collected under permits issued by the Cameroon Ministry of Scientific Research and Innovation (MINRESI: No. 00132/MINRESI/B00/C00/C10/C13) and Ministry of Forestry and Wildlife (MINFOF: No. 1010/PRBS/MINFOF/SG/DFAP/SDVEF/SC). David Modrý is acknowledged for providing material from Dzanga-Sangha (CAR), which was collected with permits from Ministère de l’Education Nationale, de l’Alphabétisation, de l’Enseignement Supérieur et de la Recherche of the Central African Republic and the World Wildlife Fund, while the Primate Habituation Programme provided logistical support. The work of VG was supported by the Czech Science Foundation (23-07331S) and Ministry of Culture of the Czech Republic (DKRVO 2019–2023/6.VII.e, National Museum, 00023272). The authors would like to express special thanks to Ana Betancourt of the Border Biomedical Research Center (BBRC) Genomics Analysis Core Facility for services and facilities provided. This work was supported by Grant 5U54MD007592 from the National Institute on Minority Health and Health Disparities (NIMHD), a component of the US National Institutes of Health (NIH).

Disclosure statement

No potential conflict of interest was reported by the author(s).