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| Microhyla nakkavaram Garg, Sivaperuman, Gokulakrishnan, Chandramouli & Biju, 2022 DOI: 10.6620/ZS.2022.61-02 |
Recent studies on frogs of the Microhyla heymonsi species complex have demonstrated that high genetic variation exists among its various known populations from regions across Asia. We assessed the taxonomic identity of the Nicobar population of Microhyla cf. heymonsi and compared it to the typical Microhyla heymonsi from Taiwan and the two recently described species in this complex from Vietnam. Our study demonstrates that the Nicobar population is both genetically and morphologically divergent and warrants recognition as a new species, which we formally describe here as Microhyla nakkavaram sp. nov. The new species is closely related to M. daklakensis, M. heymonsi, and M. ninhthuanensis, but diagnosable from all three species by a suite of morphological characters, such as the presence of two small tubercles at mid-dorsum along with ( )-shaped markings, length of finger I longer than half the length of finger II, presence of three distinct metacarpal tubercles on hand, rudimentary foot webbing, as well as its slender body shape, granular dorsal skin texture, and other colour characters and body markings. Statistical analyses based on multiple morphometric characters also clearly separate our new taxon from M. heymonsi, with which it was previously confused. Our phylogenetic analyses based on the mitochondrial 16S rRNA locus find Microhyla nakkavaram sp. nov. to be nested in the Microhyla achatina species group, where it is delimited as a distinct species. This lineage shows genetic distances of ≥ 3.5% from all the other known congeners. Currently, the known distribution of the new taxon is restricted to the southernmost group of Nicobar Islands—Great Nicobar, Kondul, and Little Nicobar—where it is found in abundance across a wide range of habitats during the monsoon season. Our study underlines the need to reassess the identity of all the known populations of M. ‘heymonsi’ from other regions in Southeast and East Asia. To facilitate future taxonomic work in the light of our and other recent findings, we also provide a detailed redescription and revised diagnosis for M. heymonsi based on morphological examination of its century-old type material originating from Taiwan.
Key words: Amphibia, Microhyla heymonsi, Integrative taxonomy, Mitochondrial DNA, Species complex.
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| The holotype of Microhyla nakkavaram sp. nov. (ZSI/ANRC/T/14215). |
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| Colour variation in life among the paratype and referred specimens of Microhyla nakkavaram sp. nov. A–E: Paratypes: A: ZSI/ANRC/ T/14216; B: ZSI/ANRC/T/14220; C: ZSI/ANRC/T/14217; D: ZSI/ANRC/T/14218; E: ZSI/ANRC/T/14219; F: Referred specimen: SDBDU 2019.4203. Seven aspects are depicted in clockwise order: dorsal view, ventral view, lateral view, dorsal view of cloacal region, posterior view of cloacal region, ventral view of hand, and ventral view of foot. Photos: S. D. Biju. |
Microhyla nakkavaram sp. nov.
Nicobarese narrow-mouthed frog
Diagnosis: Microhyla nakkavaram sp. nov. is
diagnosed by a combination of following morphological
traits: body slender, small in size (male SVL 16–19 mm,
female SVL 21 mm); snout rounded in lateral view;
finger I longer than half the length of finger II: FI >
½FII; dorsal surface of finger and toe discs with a
median dorso-terminal groove, cover bifurcate distally;
tips of all fingers weakly dilated into discs; three
metacarpal tubercles, rounded; tibiotarsal articulation
of the straightened limb reaching up to the eye;
rudimentary webbing between toes; both inner and
outer metatarsal tubercles present; dorsum sparsely to
uniformly granular, especially in life; lateral surfaces
prominently dark blackish-brown from the snout to
nearly the groin with ash-blue mottling towards the
lower parts; a thin light coloured mid-dorsal line present
from the snout tip to the vent; presence of two small tubercles at mid-dorsum with ( )-shaped markings,
anterior one placed almost at the level of armpits, and
posterior one almost at the center of the dorsum, both
the tubercles along the mid-dorsal line (Figs. 3–4).
Phylogenetic relationship and genetic divergence:
Microhyla nakkavaram sp. nov. is a member of
the Microhyla achatina species group (Microhyla
heymonsi subgroup) and shows a well-supported sister group relationship with M. ninhthuanensis (Fig. 1). It
differs from all the genetically known congeners by
uncorrected pairwise genetic distances of ≥ 3.5% for the
16S rRNA (Table 1).
Etymology: The species name is derived from an ancient name for Nicobar Islands—‘Nakkavaram’ (meaning: the land of naked people, in Tamil language)— that finds earliest mention in the 11th century Tanjore inscriptions from the reign of Chola dynasty. The species epithet is treated as an invariable noun in apposition to the generic name.
Microhyla heymonsi Vogt, 1911
Heymon’s narrow-mouthed frog
Distribution: Possibly restricted to the islands of
Taiwan and Hainan; and Southern China, from Zhejiang
Province in the east, through southern Sichuan Province,
up to Yunnan Province in the west.
Sonali Garg, Chandrakasan Sivaperuman, G. Gokulakrishnan, S. R. Chandramouli and S. D. Biju. 2022. Hiding in Plain Sight: Rain Water Puddles in Nicobar Islands of India Reveal Abundance of a New Frog Species of the Genus Microhyla Tschudi, 1838 (Anura: Microhylidae). Zool Stud. 61:2.
