Disentangling vines: a study of morphological crypsis and genetic divergence in vine snakes (Squamata: Colubridae: Ahaetulla) with the description of five new species from Peninsular India

Abstract

We carried out a taxonomic revision of Ahaetulla species inhabiting Peninsular India, using a multiple criteria approach (including genetics, morphology, and geography). Our work included populations of the A. nasuta complex (widespread across the entire region, including the Western Ghats), the A. pulverulenta complex (in the Western Ghats, within Peninsular India) and the A. dispar complex (endemic to the Southern Western Ghats) which all revealed undocumented cryptic diversity. Here, we describe five new species and effect nomenclatural changes to some recognised taxa. In the A. nasuta complex, we describe four species from several latitudinal blocks of the Western Ghats and make nomenclatural emendations to the plains populations in the Indian peninsula. We effect nomenclatural change in the A. pulverulenta population of the Western Ghats and describe a new species from the A. dispar group. Our study highlights the use of a multi-criteria approach in unraveling cryptic diversity. This study also reveals a striking case of discordance between morphological and genetic divergence, and the way this is reflected in previous taxonomic and nomenclatural treatments of these populations.

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)

“…nov. restricted to the north (Supplementary Figure S14). Allopatric species showing shallow divergence with strong morphological and geographical separation have also been reported in other WG taxa ( Mallik et al, 2020 ; Vijayakumar et al, 2014 , 2016 ). The other four newly identified species from the beddomei clade show moderate to high divergence from the other clade members and morphological separation.…”

“…First, we identified well-supported subclades and used genetic divergence within members of each subclade to identify distinct lineages. For lineage diagnosis, we used the uncorrected pairwise distance of the 16S mitochondrial gene and classified genetic divergence in the following categories: shallow genetic divergence (1%–2%); moderate genetic divergence (2%–4%); high genetic divergence (4%–6%); and very high genetic divergence (>6%) ( Mallik et al, 2020 ; Shanker et al, 2017 ; Vijayakumar et al, 2014 ). We designated lineages with high or very high genetic divergence as species, and further examined shallow and moderately divergent species along morphological and geographical axes.…”

“…In this study, we constructed an updated phylogeny of Cnemaspis from Peninsular India, including near complete taxon sampling of WG species. We used a multi-criteria approach including molecular phylogeny, genetic distance, morphological comparison, and geographical distribution to delimit species ( Mallik et al, 2020 ; Pal et al, 2018 ; Vijayakumar et al, 2014 ). We identified multiple strongly supported clades in Cnemaspis from Peninsular India, supported by morphological evidence and geographical distribution.…”

Habitat determines convergent evolution of cephalic horns in vipers

“…Like vipers, the few snake lineages with cephalic appendages also employ ambush foraging. Nasal appendages occur in Ahaetulla (Colubridae) and Langaha (Lamprophiidae) species, two distantly related arboreal genera thought to rely on crypsis to ambush diurnal prey (Henderson & Binder, 1980; Kuchling, 2003; Tingle, 2012; Mallik et al ., 2020). Two of the three Langaha species possess both nasal and ocular appendages (Kuchling, 2003), which is comparable to the arboreal viper taxa we recorded with both characters (Figure 2).…”

Annotated checklist of the snakes of Bengaluru Urban District, Karnataka, India with notes on their natural history, distribution, and population trends over the last 150 years

“…It feeds primarily on birds and lizards (Kalki and Weiss, 2020). This species was previously considered A. nasuta, a species that is now considered endemic to Sri Lanka (Mallik et al, 2020). Due to its excellent camouflage and habitat preferences, this species does not often come into conflict with people.…”