Diversifying on the Ark: multiple new endemic lineages of dwarf geckos from the Western Ghats provide insights into the systematics and biogeography of South Asian <i>Cnemaspis</i> (Reptilia: Squamata)

Abstract

The highly speciose gekkonid genus Cnemaspis Strauch, 1887 is polyphyletic, with three distantly related and geographically isolated clades from Africa, South Asia (SA), and Southeast Asia. At present, there are 85 known species within SA Cnemaspis , although the number continues to increase rapidly with focused surveys and rigorous taxonomic work. Recent studies have provided valuable insights into the diversity and evolutionary history of SA Cnemaspis ; however, most of these studies lack sufficient sampling in the Western Ghats (WG), where the genus has its greatest diversity. We addressed this research gap by conducting extensive sampling across the WG and re-examining museum specimens, thus providing a systematic account of various extant Cnemaspis species along with their distribution and natural history. We described 12 new species and a southern WG endemic clade of SA Cnemaspis. Ten of the newly described species are endemic to the forests of the southern WG. We also identified 10 well-supported subclades that can be separated across morphological, geographic, and phylogenetic axes. A time-calibrated phylogeny and ancestral area reconstructions confirmed the Paleocene origin of SA Cnemaspis in the WG and provide insights into its evolutionary history and biogeography. The discovery of multiple endemic and deeply divergent lineages further highlights the evolutionary significance of the WG for lizards.

Three new cryptic species of South Asian Cnemaspis Strauch, 1887 (Squamata, Gekkonidae) from Karnataka, India

“…SAC are perhaps the oldest extant Indian squamate taxon with initial divergence in the Paleocene-Eocene in the Western Ghats, and are ancestrally cool adapted (Agarwal et al 2020c;Pal et al 2021). The three new species described in this paper are all from montane habitats (>800 m elevation), and while Cnemaspis tigris sp.…”

“…nov. and C. vijayae sp. nov. from the central Western Ghats takes the number of species known from the goaensis clade to five and the number of Cnemaspis described from the Western Ghats to 49 (Pal et al 2021). Sakleshpur now has a third Cnemaspis species described from its vicinity in addition to C. magnifica and C. schalleri (Khandekar et al 2020b(Khandekar et al , 2021a.…”

“…Cnemaspis species tend to have narrow distributions and most recently described species are known only from their type-localities. Many localities in the central and southern Western Ghats are known to host at least three species from divergent clades at a single locality (Khandekar et al 2021a;Pal et al 2021;Khandekar and Agarwal unpubl. data./ pers.…”

“…South Asian Cnemaspis (SAC) is an exceptionally diverse radiation of geckos that originated in the Western Ghats with species distributed in India, Sri Lanka, Myanmar, Thailand, Sumatra and associated islands off its west coast (Iskandar et al 2017;Lee et al 2019;Agarwal et al 2020aAgarwal et al , 2020cAgarwal et al , 2021aAmarasinghe et al 2021;Karunarathna et al 2021;Khandekar et al 2021a). Con-sidered part of the paraphyletic gekkonid genus Cnemaspis Strauch, 1887(Grismer et al 2014, this is the oldest extant Indian squamate clade with its most recent common ancestor dating back to ~62 million years ago (Agarwal et al 2020c;Pal et al 2021) and is represented by more than 100 species with over 50 % of its diversity restricted to India (68 species) followed by Sri Lanka (40 species) (Am-arasinghe et al 2021;Khandekar et al 2021b;Pal et al 2021;Uetz et al 2021). The taxonomic revision of Indian and Sri Lankan Cnemaspis by Manamendra-Arachchi et al (2007) and published phylogenies have led to a steady surge in new species descriptions from India-more than doubling the known diversity of the genus in less than the past four years (Sayyed et al 2018(Sayyed et al , 2019(Sayyed et al , 2021Cyriac et al 2018Cyriac et al , 2020Khandekar, 2019;Khandekar et al 2019aKhandekar et al , 2019b, Murthy et al 2019Agarwal et al 2020aAgarwal et al , 2020bAgarwal et al , 2020cAgarwal et al , 2021bChandramouli, 2020;Sayyed and Sulakhe 2020;Pal et al 2021).…”

“…Con-sidered part of the paraphyletic gekkonid genus Cnemaspis Strauch, 1887(Grismer et al 2014, this is the oldest extant Indian squamate clade with its most recent common ancestor dating back to ~62 million years ago (Agarwal et al 2020c;Pal et al 2021) and is represented by more than 100 species with over 50 % of its diversity restricted to India (68 species) followed by Sri Lanka (40 species) (Am-arasinghe et al 2021;Khandekar et al 2021b;Pal et al 2021;Uetz et al 2021). The taxonomic revision of Indian and Sri Lankan Cnemaspis by Manamendra-Arachchi et al (2007) and published phylogenies have led to a steady surge in new species descriptions from India-more than doubling the known diversity of the genus in less than the past four years (Sayyed et al 2018(Sayyed et al , 2019(Sayyed et al , 2021Cyriac et al 2018Cyriac et al , 2020Khandekar, 2019;Khandekar et al 2019aKhandekar et al , 2019b, Murthy et al 2019Agarwal et al 2020aAgarwal et al , 2020bAgarwal et al , 2020cAgarwal et al , 2021bChandramouli, 2020;Sayyed and Sulakhe 2020;Pal et al 2021). Currently, SAC is the country's most diverse reptilian clade and recently surpassed the rhacophorid frog genus Raorchestes Biju, Shouche, Dubois, Dutta and Bossuyt, 2010 that includes 65 species (Frost 2022) to become the most diverse Indian vertebrate genus (Vijayakumar et al 2014;Garg et al 2021;Khandekar et al 2021b;Sayyed et al 2021).…”