Substrate specialisation drives an unexpectedly diverse radiation in barking geckos (Ptenopus: Gekkonidae)

• Published in: Molecular phylogenetics and evolution 2024-08, Vol.197, p.108104, Article 108104
• Main Authors: Becker, Francois S., Alexander, Graham J., Tolley, Krystal A.
• Format: Article
• Language: English
• Subjects: Africa, Southern; Animals; Bayes Theorem; DNA, Mitochondrial - genetics; Gekkonidae; Genetic Speciation; genus; gravel; Lizards - classification; Lizards - genetics; Models, Genetic; paraphyly; Phylogeny; regression analysis; sand; Sequence Analysis, DNA; Southern Africa; species; substrate specificity
• ISSN: 1055-7903; 1095-9513; 1095-9513
• DOI: 10.1016/j.ympev.2024.108104

[Display omitted] •Genus Ptenopus: Gekkonidae (barking geckos) is unexpectedly diverse, containing at least five unrecognised taxa in addition to the three recognised species.•Multiple species and genetically divergent populations occur parapatrically at substrate transition zones, where soft sand and hard soils occur in parallel.•Speciation was primarily driven by divergent substrate specialisation, including several speciation events in progress. Barking geckos (genus Ptenopus) are terrestrial, burrowing lizards endemic to southern Africa, currently with three recognised species. Two species are range-restricted (P. kochi and P. carpi) and display clear differences in substrate preference (soft sand vs. hard gravel). The third and most widespread species, P. garrulus, occurs on a variety of substrates of differing hardness, across potential geographic barriers, and over a steep climatic gradient. Variations in morphology and advertisement calls indicates that P. garrulus may be a species complex. Two subspecies of P. garrulus are currently recognised: P. g. maculatus and P. g. garrulus. To investigate species boundaries, we produced the first comprehensive phylogeny for the genus. We used a novel application of multiple regression on matrices models to assess multiple environmental drivers of diversification, as contrasted to isolation by distance. We show that P. kochi, P. carpi, and P. g. garrulus are valid species, but that P. g. maculatus is a paraphyletic complex of five previously unrecognised taxa. Specialisation onto different substrates was likely the main driver of divergence, with parapatric occurrence of two to four clades occurring at each of the three substrate transition zones identified a priori. The region encompasses diverse bioclimatic regions and potential geographic barriers, and these likely played a role in some divergence events.