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| Raorchestes keirasabinae Garg, Suyesh, Das, Bee & Biju,. 2021 DOI: 10.7717/peerj.10791 |
Abstract
The genus Raorchestes is a large radiation of Old World tree frogs for which the Western Ghats in Peninsular India is the major center for origin and diversification. Extensive studies on this group during the past two decades have resolved long-standing taxonomic confusions and uncovered several new species, resulting in a four-fold increase in the number of known Raorchestes frogs from this region. Our ongoing research has revealed another five new species in the genus, formally described as Raorchestes drutaahu sp. nov., Raorchestes kakkayamensis sp. nov., Raorchestes keirasabinae sp. nov., Raorchestes sanjappai sp. nov., and Raorchestes vellikkannan sp. nov., all from the State of Kerala in southern Western Ghats. Based on new collections, we also provide insights on the taxonomic identity of three previously known taxa. Furthermore, since attempts for an up-to-date comprehensive study of this taxonomically challenging genus using multiple integrative taxonomic approaches have been lacking, here we review the systematic affinities of all known Raorchestes species and define 16 species groups based on evidence from multi-gene (2,327 bp) phylogenetic analyses, several morphological characters (including eye colouration and pattern), and acoustic parameters (temporal and spectral properties, as well as calling height). The results of our study present novel insights to facilitate a better working taxonomy for this rather speciose and morphologically conserved radiation of shrub frogs. This will further enable proper field identification, provide momentum for multi-disciplinary studies, as well as assist conservation of one of the most colourful and acoustically diverse frog groups of the Western Ghats biodiversity hotspot.
Raorchestes drutaahu sp. nov.
Fast-calling Shrub Frog
Etymology. The species name is derived from Sanskrit ‘druta’ (meaning fast) and ‘ahu’ (meaning call), referring to the fast-pulsatile calls of the new species. The species epithet drutaahu is treated as an invariable noun in apposition to the generic name.
Distribution and natural history. Raorchestes drutaahu sp. nov. is endemic to the Western Ghats and currently known only from elevations ranging between 1,000 to 1,450 m asl at two localities: Kadalar in Idukki district (south of Palghat gap) and Siruvani in Palakkad district (north of Palghat gap). The species has been observed in forest areas, either on grassland-shola fringes or fragmented forest patches near plantations. Individuals were located on leaves of short shrubs at heights of 0.5–1.5 m.
Raorchestes kakkayamensis sp. nov.
Kakkayam Shrub Frog
Etymology. The species is named after the place Kakkayam, where the type series was collected.
Distribution and natural history. Raorchestes kakkayamensis sp. nov. is endemic to the Western Ghats and currently known only from its type locality (Kakkayam) in Kozhikode district, north of Palghat gap in Kerala State. The species was observed inside a primary forest patch and adjoining secondary forest areas at an elevation of 750 m asl. Individuals were located on the ground leaf litter or found perching on vegetation 1–3 m high.
Raorchestes keirasabinae sp. nov.
Keira’s Shrub Frog
Etymology. The species is named after a young nature lover Keira Sabin, in appreciation of the long-time support and commitment of the Andrew Sabin Family Foundation towards amphibian research and conservation around the world. The species epithet keirasabinae is treated as a noun in the genitive case.
Distribution and natural history. Raorchestes keirasabinae sp. nov. is endemic to the Western Ghats and currently known from elevations of 100–1,000 m asl south of Palghat gap. It has been observed at Agasthyamalai Biosphere Reserve (Chathankod-Makki, Ponmudi, Peppara Wildlife Sanctuary, and Shendurney Wildlife Sanctuary) in Thiruvananthapuram and Kollam districts, and Periyar Tiger Reserve in Idukki district of Kerala State. Since the species inhabits the highest canopy layers and cannot be located easily, it could have a wider geographical range in the Western Ghats regions south of Palghat gap, both in Kerala and the adjoining State of Tamil Nadu. The vocalisations of this species have not been recorded and analysed.
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| Figure 16: Raorchestes chromasynchysi species group. (A) Phylogenetic relationships and major morphological characters for members of the group: (1) adult size range (male SVL 20–35 mm, female SVL 27–37 mm); (2) dorsum with a horny ridge extending from the snout tip to the vent; (3) presence of lingual papillae; (4) foot webbing moderate to large, up to or well beyond the second subarticular tubercle on either side of toe IV. (B and C) Male calls in members of the group: Calling individual, followed by a call oscillogram (above) and spectrogram (below) for R. chromasynchysi and R. silentvalley (1 s section showing a single call for each species). (D and E) Adult male, followed by a call oscillogram (above) and spectrogram (below) for R. ravii and R. sanjappai sp. nov. (0.1 s section showing a single call for each species). (F) Adult male of R. vellikkannan sp. nov. (call not studied). (G–K) Eye colour and pattern in five members of the group. (L) Geographical distribution of members of the group; species range colours on the map correspond to the square colours indicated alongside each species label in (B)–(F). |
Raorchestes sanjappai sp. nov.
Sanjappa’s Shrub Frog
Etymology. The species is named after Dr. M. Sanjappa, a renowned Indian Botanist and former Director of the Botanical Survey of India. The species name is in appreciation of his taxonomic contributions as well as generous support to SDB during the initial phases of his research career. The species epithet sanjappai is treated as a noun in the genitive case.
Distribution and natural history. Raorchestes sanjappai sp. nov. is endemic to the Western Ghats and currently known only from an altitude of about 750 m asl at its type locality (Periya) that lies north of Palghat gap in the Wayanad district of Kerala State. The species was observed inside secondary forests and individuals were located on vegetation up to 3 m high during the breeding season.
Raorchestes vellikkannan sp. nov.
Silver-eyed Shrub Frog
Etymology. The species name is derived from Malayalam (the language of Kerala State where the type series were collected) ‘velli’ (meaning silver) and ‘kannu’ (meaning eye) referring to the silver colour of the iris in this species. The species epithet vellikkannan is treated as an invariable noun in apposition to the generic name.
Distribution and natural history. Raorchestes vellikkannan sp. nov. is endemic to the Western Ghats and currently known only from its type locality (Singappara, Siruvani) and surrounding regions of the Silent Valley National Park in Palakkad district of Kerala State, north of Palghat gap. This species was observed inside primary forests and individuals were found on vegetation up to 4 m high during the breeding season. The vocalisations of this species have not been recorded and analysed.
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| Figure 23: Ungrouped species. (A) Phylogenetic position of two ungrouped species, Raorchestes echinatus and R. indigo. (B–E) R. echinatus: (B) Dorsolateral view.(C) Lateral view. (D) Posterior view of thighs. (E) Eye colour and pattern. (F–I) R. indigo: (F) Dorsolateral view. (G) Lateral view. (H) Posterior view of thighs. (I) Eye colour and pattern. (J) Geographical distribution of R. echinatus and R. indigo. |
Sonali Garg, Robin Suyesh, Sandeep Das, Mark A. Bee and S. D. Biju. 2021. An Integrative Approach to Infer Systematic Relationships and Define Species Groups in the Shrub Frog Genus Raorchestes, with Description of Five New Species from the Western Ghats, India. PeerJ. 9:e10791. DOI: 10.7717/peerj.10791
