Rohanixalus, Biju & Garg & Gokulakrishnan & Chandrakasan & Thammachoti & Ren & Gopika & Bisht & Hamidy & Shouche, 2020

Biju, S. D., Garg, Sonali, Gokulakrishnan, G., Chandrakasan, Sivaperuman, Thammachoti, Panupong, Ren, Jinlong, Gopika, C., Bisht, Karan, Hamidy, Amir & Shouche, Yogesh, 2020, New insights on the systematics and reproductive behaviour in tree frogs of the genus Feihyla, with description of a new related genus from Asia (Anura, Rhacophoridae), Zootaxa 4878 (1), pp. 1-55 : 27-29

Genus Rohanixalus gen. nov.

Zoobank: urn:lsid:zoobank.org:act:C5E1F838-322E-4304-BB13-348FB40B10E5

Etymology. The genus is named after Rohan Pethiyagoda, in appreciation of his contributions to herpetological and ichthyological studies in Asia. The generic epithet is derived from Rohan + genus name Ixalus Dumeìril and Bibron, 1841 (a traditional suffix in rhacophorid generic names). For nomenclatural purposes, the gender of this generic name is masculine.

Common name. Rohan’s Tree Frogs

Type species. Ixalus vittatus Boulenger, 1887 (= Rohanixalus vittatus comb. nov.)

Phylogenetic definition. Rohanixalus gen. nov. consists of the most inclusive clade that contains Rohanixalus

vittatus but not the type species of any of the currently recognised rhacophorid genera ( Beddomixalus bijui , Buergeria buergeri , Chirixalus doriae , Chiromantis xerampelina , Feihyla palpebralis , Nasutixalus jerdonii , Ghatixalus variabilis , Gracixalus gracilipes , Kurixalus eiffingeri , Leptomantis bimaculatus , Liuixalus romeri , Mercurana myristicapalustris , Nyctixalus margaritifer , Philautus aurifasciatus , Polypedates leucomystax , Pseudophilautus temporalis , Raorchestes glandulosus , Rhacophorus reinwardtii , Taruga fastigo , Theloderma leporosum , and Zhangixalus dugritei ) ( Fig. 1 ).

Diagnosis. Rohanixalus gen. nov. can be distinguished from other rhacophorid genera by the combination of following characters: small to medium-sized adults (SVL 18–29 mm); body rather slender in appearance; skin shagreened to sparsely granular; tympanum indistinct or weakly developed; vomerine teeth absent; the entire dorsum, lateral surfaces, and dorsal surfaces of limbs covered with fine dark brown speckles, some speckles clumping together to form dark irregular spots or blotches over the dorsum; a pair of prominent to faint, continuous or discontinuous, contrasting light coloured dorsolateral stripes starting from the tip of the snout, extending over the upper eyelid margins, and ending close to the vent on either side; groin and anterior and posterior parts of thigh without any prominent markings or colouration; the first two fingers opposed to the others; webbing between fingers absent, except a rudiment of web at the base between fingers III and IV; foot webbing moderate, not beyond the second subarticular tubercle on either side of toe IV; eggs laid in terrestrial bubble nests; freshly laid eggs light green in colour, unpigmented on poles ( Figs. 3 , 7 ); and egg-attendance as a possible behavioural synapomorphy.

Comparison. Rohanixalus gen. nov. differs from all other rhacophorid members by the presence of a pair of contrasting light-coloured dorsolateral stripes (with variable degree of prominence, prominent to faint, continuous or discontinuous) starting from the snout tip, extending over the upper eyelid margins, and ending close to the vent on either side (vs. absent, except in Rhacophorus lateralis ), presence of prominent and dense minute speckles throughout the dorsal and lateral surfaces of the body (including dorsum, lateral surfaces, and dorsal surface of limbs) (vs. absent), and freshly laid eggs light green (vs. creamy white, except in some members of the Feihyla vittiger group). Further, Rohanixalus differs from Philautus , Pseudophilautus , and Raorchestes in having an exotrophic mode of development with free-swimming tadpoles (vs. endotrophic or direct developing larvae), and the first two fingers opposed to the others (vs. not opposable); it differs from Beddomixalus , Chirixalus , Chiromantis , Ghatixalus , Leptomantis , Polypedates , Rhacophorus , Taruga , and Zhangixalus by eggs laid in bubble nests (vs. foam nests), and absence of vomerine teeth (vs. presence). Specifically, Rohanixalus also differs from the various foam-nesting genera individually or collectively by: relatively smaller adult size, SVL <30 mm (vs. larger, SVL> 30 mm: SVL 37–67 mm in Beddomixalus ; SVL 39–82 mm in Ghatixalus ; SVL 30–80 mm in Leptomantis ; SVL 37–85 mm in Polypedates ; SVL 30–100 mm in Rhacophorus ; SVL 32–71 mm in Taruga ; SVL 30–120 mm in Zhangixalus ), and absence of calcar on the distal end of tibia (vs. present, except in some species of Polypedates ); differs from Chirixalus by absence of dorsal lines (vs. present); differs from Chiromantis by relatively smaller adult size, SVL <30 mm (vs. larger, SVL 35–90 mm), a rudiment of web on fingers III and IV (vs. more extensive), and tympanum indistinct or weakly developed (vs. distinct); differs from Leptomantis by the first two fingers opposed to the others (vs. not opposable), absence of calcar on the distal end of tibia (vs. present), and absence of webbing between fingers, except a rudiment of web on fingers III and IV (vs. present). Further, Rohanixalus differs from Gracixalus , Kurixalus , Nasutixalus , Nyctixalus , and Theloderma by the first two fingers opposed to the others (vs. not opposed), breeding and oviposition on leaves (vs. phytotelm-breeding and oviposition on walls of tree holes, water-filled cavities, crevices, or on ground), and eggs laid in bubble nests (vs. gel encapsulated eggs). Specifically, Rohanixalus also differs from Gracixalus , Kurixalus , and Nasutixalus , by its body rather slender in appearance (vs. robust); differs from Gracixalus by absence of dorsal markings (vs. presence of ‘X’-shaped, inverted ‘V’ or ‘Y’- shaped marking) and absence of spines on upper eyelids (vs. present); differs from Kurixalus by absence of dermal fringes on forearms and tarsus (vs. present), and absence of vomerine teeth (vs. present); differs from Nasutixalus by relatively smaller adult size, <30 mm (vs. larger, 37–48mm), absence of oophagous tadpoles (vs. present), and iris without ‘X’ mark (vs. present); specifically also differs from Nyctixalus and Theloderma by absence of spines, asperities, tubercles, or warts on dorsal skin (vs. present), and tympanum indistinct or weakly developed (vs. distinct). Further, Rohanixalus differs from Mercurana by relatively smaller adult size, SVL <30 mm (vs. larger, SVL 33–41 mm), first two fingers opposed to the others (vs. non opposed), absence of vomerine teeth (vs. present), oviposition and early development on leaves (vs. ground, eggs mixed with mud in shallow ground pits), and eggs laid in bubble nests (vs. gel encapsulated eggs); differs from Feihyla by eggs laid in bubble nests (vs. jelly nests), freshly laid eggs light green and unpigmented (vs. creamy white with pigmentation on poles, except in some members of Feihyla vittiger group), and absence of a prominent white streak along the upper lip margins from below the eye up to shoulder (vs. present). Further, Rohanixalus differs from Liuixalus by eggs laid in bubble nests on leaves (vs. aquatic eggs), absence of ‘X’ shaped mark on dorsum (vs. present), and toes moderately webbed (vs. rudimentary webbing). Rohanixalus also differs from Buergeria by eggs laid in bubble nests on leaves (vs. aquatic eggs), body slender in appearance (vs. rather robust), dorsal skin without tubercles, granules, or ridges (vs. present), and absence of vomerine teeth (vs. present). Rohanixalus is thus distinguished from all 21 other currently recognised rhacophorid genera by a combination of characters, chiefly with respect to external morphology, breeding behaviour, oviposition, and development mode.

Distribution. The genus Rohanixalus gen. nov. is restricted to South, Southeast, and East Asia, where it is currently known from India: Northeastern Indian states (Arunachal Pradesh, Assam, Manipur, Nagaland, Mizoram, and Tripura) and the Andaman Islands; Bangladesh: Sylhet Division; Myanmar; Thailand; Laos; Cambodia; China (Yunnan, Guangxi, Hainan, and Tibet); Vietnam; Malaysia; and the Sumatran island of Indonesia ( Fig. 4 ).

Diversity. Currently there are eight nominal taxa in the new genus: Rohanixalus baladika ( Riyanto and Kurniati, 2014) comb. nov.; Rohanixalus hansenae ( Cochran, 1927) comb. nov.; Rohanixalus marginis ( Chan, Grismer, Anuar, Quah, Grismer, Wood, Muin, and Ahmad, 2011) comb. nov.; Rohanixalus nauli ( Riyanto and Kurniati, 2014) comb. nov.; Rohanixalus punctatus ( Wilkinson, Win, Thin, Lwin, Shein, and Tun, 2003) comb. nov.; Rohanixalus senapatiensis ( Mathew and Sen, 2009) comb. nov.; Rohanixalus shyamrupus ( Chanda and Ghosh, 1989) comb. nov.; Rohanixalus vittatus ( Boulenger, 1887) comb. nov.

Figures

FIGURE 1. Maximum Likelihood tree showing phylogenetic relationships among 124 representative taxa from all recognised genera of the subfamily Rhacophorinae. Relationships are inferred based on 1,937 bp of mitochondrial (12SrRNA, tRNAVAL, 16SrRNA) and nuclear (RHO and RAG1) genes. Numbers above and below the branches indicate Bayesian Posterior Probabilities and RAxML bootstrap support values, respectively.

FIGURE 3. Nest structure and egg clutch morphology in the closely relatedAsian genera Chirixalus, Feihyla, and Rohanixalus. A. Foam nest in genus Chirixalus: an amplected pair of C. simus on a freshly laid foam nest; B. bubble nest in genus Rohanixalus: R. vittatus female with a freshly laid egg clutch; C. jelly-nest in genus Feihyla: eggs of Feihyla fuhua; D. schematic illustration of egg clutch morphology in genus Rohanixalus; E. schematic illustration of egg clutch morphology in Feihyla palpebralis group (Feihyla sensu stricto); F. schematic illustration of egg clutch morphology in Feihyla vittiger group; G. schematic illustration of egg clutch morphology in genus Chirixalus.

FIGURE 4. Distribution of genetically confirmed records of all known Feihyla and Rohanixalus members (indicated by circles) and their respective type localities (indicated by triangles). Numbers corresponding to each species are indicated alongside the distribution spots.

FIGURE 7. Members of the genus Rohanixalus. A. Dorsolateral view of R. hansenae from the type locality, Nong Khor, Thailand; B. dorsolateral view of R. marginis (holotype) from Perlis State Park chalets, Perlis, Peninsular Malaysia; C. dorsal view of R. cf. nauli, from Batang Gadis National Park, North Sumatra, Indonesia with a jelly-nest; D. dorsolateral view of R. cf. nauli, from Batang Gadis National Park, North Sumatra, Indonesia; E. dorsolateral view of R. cf. nauli, from Bukit Barisan Forest Park, North Sumatra, Indonesia; F. dorsolateral view of R. punctatus (Paratype, JBS 9274) from Gwa, Rakhine State, Myanmar (CC Public domain 3.0; AmphibiaWeb); G. dorsolateral view of R. vittatus from Rangat, Middle Andaman Islands, India; H. dorsolateral view of R. senapatiensis from Manipur, India; I. dorsolateral view of R. shyamrupus from Namdapha, Arunachal Pradesh.