Ahaetulla dispar ( Günther, 1864 )

Mallik, Ashok Kumar, Srikanthan, Achyuthan N., Pal, Saunak P., D’Souza, Princia Margaret, Shanker, Kartik & Ganesh, Sumaithangi Rajagopalan, 2020, 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, Zootaxa 4874 (1), pp. 1-62 : 40-42

Ahaetulla dispar ( Günther, 1864)

Tragops dispar Günther, 1864

Dryophis dispar — Boulenger, 1890

Ahaetulla dispar— Savage, 1952

Referred material. CESS 187; adult female, CESS 188; adult male; CESS 189; adult male; Anaimudi shola NP, Kerala; Coll. Ashok Kumar Mallik, 2011.

CESS 261; adult (sex unknown); Achankovil / Devarmala; Coll. Saunak P. Pal, 2011.

Etymology. Named after its disparate colouration, a sexually dichromatic species with green males and predominantly brown adult females (one of the earliest known dichromatic snake see Günther, 1864; Darwin 1871 contra Mohapatra et al. 2017).

Diagnosis.

1. Phylogenetically, Ahaetulla dispar (L11) is closely related to its sister, Ahaetulla travancorica sp. nov. (L12). The clade comprising Ahaetulla dispar and Ahaetulla travancorica sp. nov. shares ancestry with an-other clade comprising lineage L3–L6 (from the Western Ghats) and Ahaetulla nasuta (L2 from Sri Lanka) ( Fig. 1 ).

2. There is a moderate level (4.1% in Cytb & 1.1% in 16S) of genetic divergence between A. dispar and Ahaet-ulla travancorica sp. nov.

3. Ahaetulla dispar differs from Ahaetulla travancorica sp. nov. by possessing 0–1 loreals on each side of the head as compared to 2 loreals in Ahaetulla travancorica sp. nov., 9 infralabials in A. dispar (vs. 7–8 in Ahaetulla travancorica sp. nov.), no keels on the dorsal row of scales (vs. mild keels present) ( Fig. 21 ).

4. Geographically, both A. dispar and A. travancorica sp. nov. are separated from each other by the Shencot-tah Gap located in the Southern Western Ghats. Ahaetulla dispar occupies a range to the north of the Shen-cottah gap, while Ahaetulla travancorica sp. nov. is distributed to the south of the gap. Ahaetulla dispar predominantly occurs in higher (> 1400 m asl) elevations compared to the largely parapatric A. isabellina comb. nov. that occurs at lower (<1200 m asl) elevations.

Description of Referred Material CESS188. Adult of total length 633 mm; dissected; very slender, partially laterally compressed body with snout to vent length 410 mm; tail length 223 mm; relative tail length 0.35; ventrals 147 notched with keels; subcaudals 113 divided; cloacal scale divided; relatively long and slender tail; dorsal scale rows in 15-15-13 rows of smooth, obliquely disposed scales; head very distinct from neck with head length 21 mm; transversely oval eyes with horizontal pupil, with a horizontal diameter of 3.2 mm and vertical diameter of 1.6 mm; distance from nostril to eye 5.1 mm; distance from snout to eye 6.5 mm; supralabials 8 (both left and right) with the 6 th supralabial being the largest, 5 th supralabial in contact with the eye; 4 th supralabial divided; infralabials 9 (both left and right);1 st, 2 nd, 3 rd and 4 th infralabials in contact with anterior genials; 4 th and 5 th infralabials in contact with posterior genials; mental scale wedged in between 1 st pair of infralabials not in contact with genials; nasal scale 1 (both left and right); loreals absent; pre-suboculars 2 (both left and right); pre-ocular 1 (both left and right); postoculars 2; sub-oculars absent; temporal 1+2+2 (both left and right); prefrontal scale in contact with pre-oculars; preventrals 2.

Colour in life. Dorsum dark green to olive green; rostral, infralabials, venter white to yellowish green at midbody; yellow ventral stripe; light yellow stripes along keels at centre, slight discolouration in the pre-ocular; interscalar skin white with black and white anteriorly-converging bars; eyes golden yellow with black speckles; concentration of black speckles both in anterior and posterior end of horizontal pupil bordered silver; tail, subcaudals light green.

Colour in preservative. Dorsum dark green to olive green; rostral, infralabials, venter light blue to white; white to yellowish white ventral stripe along the notched ventral keels; whitish stripes along ventrals at centre; slight discolouration in the pre-ocular; inter-scalar skin with black and white anteriorly-converging bars; eyes yellow clouded with white and black speckles; concentration of black speckles both in the anterior and posterior ends of a dilated pupil.

Variations (also see Whitaker & Captain, 2004 [part]; Chandramouli & Ganesh, 2010 [part]). This species is reported to have the following variations: ventrals 139–159 notched with keels (136–156 in Smith (1943)); subcaudals (males) 110–113, divided, (females) 103–125, divided, (84–119 in Smith (1943)); dorsal scale rows in 15-15-13 rows of smooth, obliquely disposed scales; supralabials 8 with 5 th or 6 th being the largest; 4 th or 5 th supralabial in contact with the eye; sometimes both 4 th and 5 th supralabial in contact with the eye; 4 th supralabial divided; loreal 1 (1–2 in Smith (1943)), loreals sometimes absent; infralabials 9; pre-suboculars 1–2; pre-ocular 1 (both left and right); postoculars 2; sub-oculars absent; temporals 1+2, 2+2 or 2+3.

Maxillary arch dentition. Arched with a dip in the arch towards diastema; 12 teeth perpendicular to maxilla, curving inwards; prediastemal teeth 8, postdiastemal teeth 4, observable gradual tooth size increase in prediastemal tooth set with the largest teeth precursing the last teeth of the prediastemal tooth set; diastema very short, just 1 tooth-socket wide; suffixed with a set of 2 smaller teeth followed by last grooved pair of large teeth ( Fig. 6i ).

Distribution and habitat. It is distributed in the Southern Western Ghats starting from Anaimalai hills and extending towards the region north of the Shencottah Gap. We doubt its purported presence in Nilgiri-Waynad, as has been mentioned in Hutton & David (2009). As a high elevation shola-grassland specialist, this species is found above 1400 msl. The snake is found predominantly in grasslands, exhibiting a terrestrial lifestyle similar to A. travancorica sp. nov. and A. perroteti .

Figures

FIGURE 1. Maximum likelihood tree generated from three mitochondrial genes shows a number of new lineages (L1–L13) identified in our study. The lineages are marked with grey bars which represent the criteria used to delimit species boundaries, where three gene bPTP (P3), genetic p-distance (GD), morphological separation (M) and geographic isolation (G) are used to predict the number of putative lineages. The nodes below 70% parametric bootstrap support are indicated with asterisk (*). “+” indicates that the status of A. nasuta cf. isabellina needs further work (see Deepak et al. 2019).

FIGURE 6. Ahaetulla lineages in Peninsular India and Sri Lanka showing side-by-side comparison of their superficial head morphology and maxillary dentition. (From the top) (a) Ahaetulla farnsworthi sp. nov. (b) A. isabellina comb. nov. (c) A. malabarica sp. nov. (d) A. borealis sp. nov. (e) A. nasuta (f) A. oxyrhyncha comb. nov. (g) A. sahyadrensis nom. nov. (h) A. travancorica sp. nov. (i) A. dispar & A. travancorica sp. nov. (j) A. perroteti (1) Ahaetulla farnsworthi sp. nov. (2) A. isabellina comb. nov. (3) A. malabarica sp. nov. (4) A. borealis sp. nov. (5) A. nasuta (6) A. oxyrhyncha comb. nov. (7) A. pulverulenta (8) A. sahyadrensis nom. nov. (9) A. dispar (10) A. travancorica sp. nov. (11) A. perroteti.

FIGURE 21. Images of Ahaetulla dispar. Live uncollected individual from High Wavy Mts.(a) Head lateral, (b) Head Dorsolateral, (c) Full body image (live) from High Wavy, (d) Threat display of CESS188 from Anamudi Hills, (e) Habitat of A. dispar, Eravikulam.