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| Craspedocephalus travancoricus Mallik, Srikanthan, Ganesh, Vijayakumar, Campbell, Malhotra & Shanker, 2021 DOI: 10.3897/vz.71.e66239 |
Abstract
Asian pit vipers belonging to the genus Craspedocephalus are a complex group of vipers, distributed in South and Southeast Asia. Their taxonomy is unresolved in many lineages across their distributional range. Here, we reassess the taxonomy and systematics of pit vipers of the genus Craspedocephalus in Peninsular India based on extensive field sampling, in particular in the Western Ghats. We build and expand on the previous findings of genetic relatedness between the peninsular Indian lineages with the Sundaic clade (C. puniceus complex) with greater evidence, based on additional taxa sequenced herein. We reconstruct the phylogeny of the group using three mitochondrial genes and delineated lineages using coalescent species delimitation methods. We then used multiple criteria including genetic divergence and separation in morphological and geographic space to designate taxonomic units. Our work revealed the presence of a South Asian radiation of the clade Craspedocephalus, with a few Sundaic members. Our study reveals the systematic relationships of four Peninsular Indian species of Craspedocephalus, including Peltopelor macrolepis and C. strigatus, sequenced here for the first time, that are classified or confirmed as members of Craspedocephalus. Hence, we place the genus Peltopelor in the synonymy of Craspedocephalus. Using our multi-criteria approach, we delimit four new cryptic evolutionary lineages within the Western Ghats escarpment of Peninsular India. These cryptic lineages belong to the C. malabaricus, C. gramineus and C. macrolepis complexes and are geographically and/or ecologically (in terms of habitat association) distinct from their sister lineages across their distributional range, while others are separated in morphological space. Our new phylogenetic tree and delimitation analysis thus reveals the presence of multiple clades with several cryptic lineages separated by geographical barriers or habitat association.
Keywords: Craspedocephalus, cryptic species, geographical barriers, phylogenetics
Viperidae Oppel, 1811
Crotalinae Oppel, 1811
Craspedocephalus Khul & Hasselt, 1822
Craspedocephalus macrolepis complex
This species complex can be distinguished from regional congeners as follows: head scales large, shield-like (vs. as small as body scales in the C. gramineus, C. malabaricus complexes and C. strigatus); midbody dorsal scale rows < 19 (vs. 21 or more in the C. gramineus, C. malabaricus complexes and C. strigatus); last rows of costal scales abutting ventrals on either side smaller than rest of the dorsal scale rows (vs. larger in all other congeners throughout the range of the genus); 2nd supralabial bordering the anterior margin of loreal pit (vs. not so in C. strigatus); supraoculars undivided (vs. frequently divided in the C. malabaricus complex); subcaudals of the tail tip bluish (vs. blackish in the C. malabaricus complex).
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| Craspedocephalus macrolepis comb. nov. in life, showing: (A) juvenile entire view from High Wavy Mountains, (B) close up of hindbody and tail, (C) entire lateral view, (D) head dorsal view, (E) head and forebody lateral view; from Eravikulam, Anaimalai range. |
Craspedocephalus macrolepis (Beddome, 1862)
Lineage diagnosis (redefined herein):
Within the C. macrolepis complex, C. macrolepis s. str. (L6) can be distinguished as follows: in having higher dorsal scale rows: 13–19 (vs. 10–14 in L7); lower ventral count 133–140 (vs. 150 in L7). Craspedocpehalus macrolepis (L6) is allopatric with its sister taxon (L7), from which it has a shallow genetic divergence (3.7% at cyt b and 0.7–1.0% at 16S rRNA). The low level of genetic divergence is the lowest genetic break between any the lineages inferred here (See Supplementary File 5: Table S4). This shallow genetic break coincides with a physical barrier (Shencottah gap) for these lineages.
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Figure 7. Craspedocephalus peltopelor sp. nov. in life showing: (A) entire lateral view, (B) entire dorsal view, (C) entire dorsolateral view, (D) head and forebody lateral view; from Kalakkad-Mundunthurai, Agasthyamalai, (E) entire front view; from Agasthyakoodam, Agasthyamalai. |
Craspedocephalus peltopelor sp. nov.
Etymology: Named after Günther’s erstwhile generic nomen that alludes to the shield-like, large scales (peltē: shield/scale, pelor (o)-: a term meaning monstrous [or literally huge], in Greek).
Lineage diagnosis: A lineage belongs to the C. macrolepis complex. Differs from C. macrolepis in having lower dorsal scale rows 10–14 (vs. 13–19); higher ventral scale counts 150 (vs. 133–143). The new species is geographically separated from C. macrolepis by the Shencottah gap in the Southern Western Ghats. Craspedocephalus peltopelor sp. nov. (L7) has a shallow genetic divergence (3.7% at cyt b and 0.7–1.0% at 16S) from C. macrolepis (L6).
Habitat: A typically arboreal (rarely semi-terrestrial) species (Ishwar et al. 2001, Seshadri, 2012) that is found in high elevation shola forests (tropical montane stunted rainforests) bordering the high elevation grasslands. Due to anthropogenic changes to the landscape, this species is also sometimes found in cultivated landscapes such as tea estates and coffee plantations. Found at elevations from about 1200 m asl to 1868 m asl.
Distribution: Endemic to the southern Western Ghats, south of the Shencottah gap. Geographically separated from its sister species, C. macrolepis that inhabits the ranges to the north of the Shencottah gap. Found throughout the high elevations of the Agasthyamalai hills.
Craspedocephalus malabaricus complex
This species complex can be distinguished from regional congeners as follows: head scales as small as body scales (vs. large, shield-like in the C. macrolepis complex); midbody dorsal scale rows 21–23 (vs. <19 in the C. macrolepis complex); last rows of costal scales abutting ventrals on either sides larger than rest of the dorsal scale rows (vs. smaller in the C. macrolepis complex); 2nd supralabial bordering the anterior margin of loreal pit (vs. not so in C. strigatus); supraoculars often divided or scale sutures with an indented margin (vs. undivided in the remaining, regional congeners); subcaudals of tail tip blackish (vs. bluish in the C. gramineus and C. macrolepis complexes). Lineages within Craspedocephalus malabaricus group appear to be morphologically cryptic, and do not differ in scalation or external morphological characters, but show geographical separation and are deeply genetically divergent.
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| Figure 10. Craspedocephalus malabaricus in life, showing: (A) orange morph entire dorsal view (Agumbe), (B) purple morph (Anshi), (C) maroon morph (Agumbe), (D) cream morph (Amboli), (E) green morph (Amboli), (F) yellow morph (Anshi) & (G) brown morph (Anshi). |
Craspedocephalus malabaricus (Jerdon, 1854)
Etymology: The specific epithet malabaricus is a toponym, alluding to its type locality - the Malabar region of the Western Ghats.
Lineage diagnosis (redefined herein):
A lineage of the C. malabaricus complex, C. malabaricus s. str. (L5) is here restricted only to populations north of the Palghat Gap. This nominotypical population is 8.3–9% and 1.2–2.2% divergent at cyt b and 16S respectively, from those south of the Palghat Gap (L3 & L4), recognised here as two nominate taxa: C. anamallensis (Günther, 1864) and Craspedocephalus travancoricus sp. nov. (see below). These taxa are allopatric with respect to each other and C. malabaricus.
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| Figure 13. Craspedocephalus anamallensis in life, showing: (A) brown morph front view, from Top Slip, (B) green morph, from Kottaimalai, (C) grey morph, from Nelliyampathy, (D) & (E) olive morphs from Top Slip; entire dorsolateral views. |
Craspedocephalus anamallensis (Günther, 1864)
Etymology: The specific epithet anamallensis is a toponym, alluding to its type locality - the Anamalai hills of the Southern Western Ghats.
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| Craspedocephalus travancoricus sp. nov. in life, showing: (A) brown morph entire front view, (B) green/brown morph entire dorsal view, (C) orange morph front view, (D) green morph lateral view, (E) green morph dorsal view, (F) brown morph lateral view, (G) grey/black morph dorsolateral view; from Ponmudi hills, Kerala. |
Craspedocephalus travancoricus sp. nov.
Etymology: Toponym, named after its distribution in the far south of the Western Ghats, in the southern parts of the ‘Travancore’ hill ranges.
Lineage diagnosis: A cryptic lineage belonging to the C. malabaricus complex, this lineage (L4) is genetically divergent from C. malabaricus (L5) by 9% & 2.2% and from C. anamallensis (L3) by 7.1 & 1.5% at cyt b and 16S respectively. This lineage is also allopatric with its related taxa C. malabaricus occurring north of the Palghat Gap and is immediately allopatric with C. anamallensis distributed just north of its distribution range, north of the Shencottah Gap.
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| (A) Craspedocephalus gramineus in life, entire lateral view (Thamini, Pune), (D) Craspedocephalus occidentalis comb. nov. in life, entire lateral view; Coorg, Karnataka. |
Craspedocephalus gramineus complex
This species complex can be distinguished from regional congeners as follows: head scales as small as body scales (vs. large, shield-like in the C. macrolepis complex); midbody dorsal scalerows 21–23 (vs. <19 in C. macrolepis complex); last rows of costal scales abutting ventrals on either sides larger than rest of the dorsal scale rows (vs. smaller in the C. macrolepis complex); 2nd supralabial bordering the anterior margin of loreal pit (vs. not so in C. strigatus); supraoculars undivided (vs. often divided or with indented scale in the C. malabaricus complex); subcaudals of tail tip bluish (vs. blackish in the C. malabaricus complex).
Craspedocephalus gramineus (Shaw, 1802)
Etymology: gramineus, ‘grassy’ in Latin, alluding to its grass-green dorsal colouration.
Craspedocephalus occidentalis (Pope & Pope, 1933), comb. nov.
Etymology: Latin, for ‘western’, in allusion to its western distribution range, compared to S.E. Asia.
Craspedocephalus strigatus (Gray, 1842)
Etymology: Latinized from its stem word ‘strigate’ alluding to the pattern streaked with colourful, alternate, transverse bars.
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| New lineages (green bars) are depicted within Craspedocephalus gramineus, C. malabaricus and the C. macrolepis species complex along with the other species from the Peninsular India. The clade comprising C. macrolepis and C. peltopelor sp. nov. is sister to the clade comprising all other members of Peninsular Indian Craspedocephalus (II). The Western Ghats C. malabaricus complex includes C. malabaricus, C. anamallensis and C. travancoricus (IV). C. trigonocephalus from Sri Lanka is nested within the Western Ghats sub-clade (III) along with C. strigatus, C. gramineus and C. occidentalis (V). Clade-I comprises species from Southeast Asia. |
Ashok Kumar Mallik, Achyuthan Needamangalam Srikanthan, Sumaithangi Rajagopalan Ganesh, Seenapuram Palaniswamy Vijayakumar, Patrick D. Campbell, Anita Malhotra and Kartik Shanker. 2021. Resolving Pitfalls in Pit Viper Systematics – A Multi-criteria Approach to Species Delimitation in Pit Vipers (Reptilia, Viperidae, Craspedocephalus) of Peninsular India reveals Cryptic Diversity. Vertebrate Zoology. 71: 577-619. DOI: 10.3897/vz.71.e66239
