The island of Borneo lies within one of the most biodiverse regions in the world. Despite this, its documented gekkonid diversity is not commensurate with other areas of Southeast Asia. The megadiverse genus Cyrtodactylus is especially underrepresented. Limestone-karst ecosystems, in particular, harbor many endemic Cyrtodactylus species, but only one karst-dwelling species is currently recognized from Borneo. This paper adds two additional karst-dwelling Cyrtodactylus species-C. muluensis sp. nov. and C. limajalur sp. nov.-from Sarawak, Malaysia. Cyrtodactylus muluensis sp. nov. is endemic to Gunung Mulu and is distinguished from its congeners by having a precloacal groove, 31-38 ventral scales, a maximum SVL of at least 88 mm, enlarged subcaudals, 19-20 subdigital lamellae, and a banded dorsal body pattern. Cyrtodactylus limajalur sp. nov. is endemic to the Serian region and is distinguished from its congeners by having 33-42 ventral scales, enlarged subcaudals, a precloacal pit, a maximum SVL of at least 94 mm, 5-6 enlarged femoral scales, 19-22 subdigital lamellae, and five distinct bands on the dorsum. Both species are phylogenetically distinct and deeply divergent from all other congeners. The description of two new karst-dwelling species highlights the need to conserve karst habitats and the endemic species they harbor.
Species delimitation using mitochondrial DNA (mtDNA) remains an important and accessible approach for discovering and delimiting species. However, delimiting species with a single locus (e.g. DNA barcoding) is biased towards overestimating species diversity. The highly diverse gecko genus Cyrtodactylus is one such group where delimitation using mtDNA remains the paradigm. In this study, we use genomic data to test putative species boundaries established using mtDNA within three recognized species of Cyrtodactylus on the island of Borneo. We predict that multi-locus genomic data will estimate fewer species than mtDNA, which could have important ramifications for the species diversity within the genus. We aim to (i) investigate the correspondence between species delimitations using mtDNA and genomic data, (ii) infer species trees for each target species, and (iii) quantify gene flow and identify migration patterns to assess population connectivity. We find that species diversity is overestimated and that species boundaries differ between mtDNA and nuclear data. This underscores the value of using genomic data to reassess mtDNA-based species delimitations for taxa lacking clear species boundaries. We expect the number of recognized species within Cyrtodactylus to continue increasing, but, when possible, genomic data should be included to inform more accurate species boundaries.
The gekkonid genus Cyrtodactylus is a highly diverse group of lizards (280 + species), which covers an expansive geographic range. Although this genus has been the focus of many taxonomic and molecular systematic studies, species on the Southeast Asian island of Borneo have remained understudied, leading to an unclear evolutionary history with cascading effects on taxonomy and biogeographic inferences. We assembled the most comprehensive multilocus Bornean dataset (one mitochondrial and three nuclear loci) that included 129 novel sequences and representatives from each known Cyrtodactylus species on the island to validate taxonomic status, assess species diversity, and elucidate biogeographic patterns. Our results uncovered a high proportion of cryptic diversity and revealed numerous taxonomic complications, especially within the C. consobrinus, C. malayanus, and C. pubisulcus groups. Comparisons of pairwise genetic distances and a preliminary species delimitation analysis using the Automatic Barcode Gap Discovery (ABGD) method demonstrated that some wide-ranging species on Borneo likely comprise multiple distinct and deeply divergent lineages, each with more restricted distributional ranges. We also tested the prevailing biogeographic hypothesis of a single invasion from Borneo into the Philippines. Our analyses revealed that Philippine taxa were not monophyletic, but were likely derived from multiple separate invasions into the geopolitical areas comprising the Philippines. Although our investigation of Bornean Cyrtodactylus is the most comprehensive to-date, it highlights the need for expanded taxonomic sampling and suggests that our knowledge of the evolutionary history, systematics, and biogeography of Bornean Cyrtodactylus is far from complete.