A new species of Micryletta frog (Microhylidae) from Northeast India.

S. D. Biju,Amir Hamidy,Abhijit Das,Sonali Garg,Eric N. Smith

doi:10.7717/peerj.7012

Abstract

We describe a new species of frog in the microhylid genus Micryletta Dubois, 1987 from Northeast India based on molecular and morphological evidence. The new species, formally described as Micryletta aishani sp. nov., is phenotypically distinct from other congeners by a suite of morphological characters such as brown to reddish-brown dorsum; dorsal skin shagreened with minute spinules; snout shape nearly truncate in dorsal and ventral view; a prominent dark streak extending from tip of the snout up to the lower abdomen; ash-grey mottling along the margins of upper and lower lip extending up to the flanks, limb margins and dorsal surfaces of hand and foot; tibiotarsal articulation reaching up to the level of armpits; absence of outer metatarsal tubercles; and absence of webbing between toes. Phylogenetic relationships within the genus are inferred based on mitochondrial data and the new taxon is found to differ from all the recognised Micryletta species by 3.5–5.9% divergence in the mitochondrial 16S rRNA. The new species was found in the states of Assam, Manipur, and Tripura, from low to moderate elevation (30–800 m asl) regions lying south of River Brahmaputra and encompassing the Indo-Burma Biodiversity Hotspot. The discovery validates the presence of genus Micryletta in Northeast India based on genetic evidence, consequently confirming the extension of its geographical range, westwards from Southeast Asia up to Northeast India. Further, for nomenclatural stability of two previously known species, Microhyla inornata (= Micryletta inornata) and Microhyla steinegeri (= Micryletta steinegeri), lectotypes are designated along with detailed descriptions.

Highlights

The Northeast region of India encompasses two globally recognised biodiversity hotspots— Himalayas in the north and Indo-Burma towards the South (Mittermeier et al, 2004), and is home to unique and diverse array of amphibians (e.g. Pillai & Yazdani, 1973; Kiyasetuo & Khare, 1986; Kamei et al, 2012; Biju et al, 2016)
The known amphibian fauna of Northeast India belongs to 11 families (Frost, 2018; AmphibiaWeb, 2018), of which Microhylidae is represented by three genera (Microhyla Tschudi, Kaloula Gray, and Uperodon Duméril and Bibron) confirmed to be present on the basis of detailed morphological and/or molecular studies (e.g. Das et al, 2005; Sengupta et al, 2009; Garg et al, 2018a, 2018b, 2018c)
The distinct phylogenetic position of M. aishani sp. nov. was concordantly recovered in all our analyses, the relationships among the four closely related and otherwise well-supported major lineages—M. aishani sp. nov., M. inornata (BPP 100, BS 97), M. steinegeri species complex (BPP 98, BS 65), and M. erythropoda + M. cf. inornata lineata (BPP 100, BS 98), were poorly resolved

Summary

Introduction

The Northeast region of India encompasses two globally recognised biodiversity hotspots— Himalayas in the north and Indo-Burma towards the South (Mittermeier et al, 2004), and is home to unique and diverse array of amphibians (e.g. Pillai & Yazdani, 1973; Kiyasetuo & Khare, 1986; Kamei et al, 2012; Biju et al, 2016). Das et al, 2005; Sengupta et al, 2009; Garg et al, 2018a, 2018b, 2018c) Another enigmatic group of microhylid frogs, genus Micryletta Dubois is believed to occur in the northeast state of Manipur based on a cursory report of Micryletta inornata Boulenger (Mathew & Sen, 2010). This species was previously reported from the Andaman Islands of India based on a subadult specimen (Pillai, 1977) that requires confirmation (Harikrishnan & Vasudevan, 2018). There are uncertainties about the identity of Micryletta species in India, and the geographical distribution of the genus and its members ( M. inornata) outside of East (Mainland China and Taiwan) and Southeast Asia (Cambodia, Indonesia, Laos, Malaysia, Myanmar, Thailand, and Vietnam) (Poyarkov et al, 2018; Garg & Biju, 2019)

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Discussion

Conclusion