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. 2019 Jul 17;14(7):e0218851.
doi: 10.1371/journal.pone.0218851. eCollection 2019.

Discovery of a deeply divergent new lineage of vine snake (Colubridae: Ahaetuliinae: Proahaetulla gen. nov.) from the southern Western Ghats of Peninsular India with a revised key for Ahaetuliinae

Ashok Kumar Mallik  1 , N Srikanthan Achyuthan  1 , Sumaithangi R Ganesh  2 , Saunak P Pal  1   3 , S P Vijayakumar  1   4 , Kartik Shanker  1
Affiliations

Discovery of a deeply divergent new lineage of vine snake (Colubridae: Ahaetuliinae: Proahaetulla gen. nov.) from the southern Western Ghats of Peninsular India with a revised key for Ahaetuliinae

Ashok Kumar Mallik et al. PLoS One. .

Abstract

The Western Ghats are well known as a biodiversity hotspot, but the full extent of its snake diversity is yet to be uncovered. Here, we describe a new genus and species of vine snake Proahaetulla antiqua gen. et sp. nov., from the Agasthyamalai hills in the southern Western Ghats. It was found to be a member of the Ahaetuliinae clade, which currently comprises the arboreal snake genera Ahaetulla, Dryophiops, Dendrelaphis and Chrysopelea, distributed in South and Southeast Asia. Proahaetulla shows a sister relationship with all currently known taxa belonging to the genus Ahaetulla, and shares ancestry with Dryophiops. In addition to its phylogenetic position and significant genetic divergence, this new taxon is also different in morphology from members of Ahaetuliinae in a combination of characters, having 12-13 partially serrated keels on the dorsal scale rows, 20 maxillary teeth and 3 postocular scales. Divergence dating reveals that the new genus is ancient, dating back to the Mid-Oligocene, and is one of the oldest persisting monotypic lineages of snakes in the Western Ghats. This discovery adds to the growing list of ancient lineages endemic to the Agasthyamalai hills and underscores the biogeographic significance of this isolated massif in the southern Western Ghats.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Phylogenetic relationship of Proahaetulla antiqua gen. et sp. nov.
(A) Chronogram shows phylogenetic relationship and time of divergence of Proahaetulla antiqua gen. et sp. nov. within family Ahaetuliinae. Asterisk (*) indicates lower posterior probability support on the node from Bayesian inference. Bar on each node indicates 95% HPD. (B) Head profile of Ahaetulla, (C) Proahaetulla gen. nov., (D) Dryophiops, (E) Dendrelaphis and (E) Chrysopelea.
Fig 2
Fig 2
(A) Maximum likelihood tree showing the relationship of Proahaetulla antiqua gen. et sp. nov. within family Ahaetuliinae. Value on each node indicates the bootstrap support. (B) Photograph of holotype specimen in life. (C) Dorsal and lateral view of head. (D) Dentition arrangement of maxillary arch.
Fig 3
Fig 3. Morphological space shared by Proahaetulla gen. nov. and all other genera of the subfamily Ahaetuliinae.
(A) A PCA showing morphological space shared by Ahaetulla and Proahaetulla gen nov. in Peninsular India. (B) A PCA of members (all five genera) of Ahaetuliinae shows the overlapping morphological space across the subfamily.
Fig 4
Fig 4. Proahaetulla antiqua gen et sp. nov. holotype (CESS 259).
(A) Dorsal view. (B) Ventral view. (C) Hemipenal profile. (D) Dorsal scales showing serrated keels. (E) Lateral view of head of paratype (CESS 318).
Fig 5
Fig 5. Habitat at the type locality of Proahaetulla antiqua gen. et sp. nov., showing montane rainforests atop Agasthyamalai hills, southern Western Ghats.
See this image and copyright information in PMC

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