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| Astrobatrachus kurichiyana
Vijayakumar, Pyron, Dinesh, Torsekar, Srikanthan, Swamy, Stanley, Blackburn & Shanker, 2019
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Abstract
The Western Ghats (WG) is an escarpment on the west coast of Peninsular India, housing one of the richest assemblages of frogs in the world, with three endemic families. Here, we report the discovery of a new ancient lineage from a high-elevation massif in the Wayanad Plateau of the southern WG. Phylogenetic analysis reveals that the lineage belongs to Natatanura and clusters with Nyctibatrachidae, a family endemic to the WG/Sri Lanka biodiversity hotspot. Based on geographic distribution, unique morphological traits, deep genetic divergence, and phylogenetic position that distinguishes the lineage from the two nyctibatrachid subfamilies Nyctibatrachinae Blommers-Schlösser, 1993 and Lankanectinae Dubois & Ohler, 2001, we erect a new subfamily Astrobatrachinae subfam. nov. (endemic to the WG, Peninsular India), and describe a new genus Astrobatrachus gen. nov. and species, Astrobatrachus kurichiyana sp. nov. The discovery of this species adds to the list of deeply divergent and monotypic or depauperate lineages with narrow geographic ranges in the southern massifs of the WG. The southern regions of the WG have long been considered geographic and climatic refugia, and this new relict lineage underscores their evolutionary significance. The small range of this species exclusively outside protected areas highlights the significance of reserve forest tracts in the WG in housing evolutionary novelty. This reinforces the need for intensive sampling to uncover new lineages and advance our understanding of the historical biogeography of this ancient landmass.
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| Figure 3: Live images of Astrobatrachus kurichiyana. Profile (A), close-up of head (B), ventral (C), dorsal (D), side-profile (E). (A and B; reference collection CESF 1567), K.P. Dinesh (C, D and E; ZSI/WRC/A/2131)
Photo: S.P. Vijayakumar.
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Amphibia Linnaeus, 1758
Anura Fischer von Waldheim, 1813
Ranoidea Batsch, 1796
Natatanura Frost et al., 2006
Nyctibatrachidae Blommers-Schlosser, 1993
Astrobatrachinae subfam. nov.
Type genus.—Astrobatrachus gen. nov.
Etymology of the generic nomen.— From the Greek astro- for ‘star,’ referring to the starry spots, more prominent on the lateral sides of the body, and batrachus meaning ‘frog’. As per the nomenclatural act the gender of genus is ‘male.’
Type species.— Astrobatrachus kurichiyana sp. nov.
Diagnosis.— This diagnosis applies to the subfamily, genus, and species. The following combination of characters can be used to diagnose this lineage from its close relatives Nyctibatrachus and Lankanectes: small to medium size (∼ 20–27 mm SVL); soft skin without ridged or wrinkled folds; fingers and toe tips with discs that are triangular in shape (Figs. 3 and 4) without circummarginal groove; upper jaws having distinct teeth; distinct and angular canthus rostralis; distinct tympanum with a prominent supra-tympanic ridge (Fig. 3); tongue lacking median papilla; short hind and fore-limbs; oblong subarticular tubercles on the fingers and toes that sometimes nearly coalesce (e.g., pedal digit III in Figs. 3 and 4); interdigital webbing on foot does not attain most proximal subarticular tubercle; absence of femoral glands; absence of nuptial pads in males; widely spaced nasal bones; a vomer separated into an anterior portion adjacent to the choana and a posterior dentigerous vomer fused to a neopalatine; omosternum not bifurcating posteriorly; a single narrow sternal element; lacking a large dorsal crest on the ilium; bluish-white spots (Figs. 3 and 4), more prominent and scattered along the lateral sides of jaws, eyelids, belly, forearms and hind limbs, and on the throat; oval-shaped pupil; orange coloration of ventral sides of belly, forelimbs and hind limbs; elliptical pupil (Fig. 3). The lineage is diagnosed easily in the field from species of Nyctibatrachus that occur sympatrically.
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| Figure 2: Phylogenetic position of Astrobatrachus kurichiyana nested within Natatanura in the clade Nyctibatrachidae.
Photo: S. P. Vijayakumar.
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| Figure 1: Geographical range (A) of the three genera, Nyctibatrachus (Nyctibatrachinae), Lankanectes (Lankanectinae) and the new genus Astrobatrachus (Astrobatrachinae subfam. nov.).
Inset maps show the type locality (B) and the narrow range (C) of Astrobatrachus kurichiyana gen et. sp. nov. Photo: S. P. Vijayakumar.
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| Figure 7: Type locality of Astrobatrachus kurichiyana. Most individuals were sighted in the montane forests except for a single individual in the grassland. Locality: Kurichiyarmala, Wayanad Plateau. Photo taken: June 2010.
Photo: S.P. Vijayakumar.
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Habits and habitat: The new species is nocturnal and found below decayed leaf litter within montane forests in the vicinity of water. One individual was caught moving in a grassland adjoining the forest tract (Fig. 7). On the forest floor, where most individuals were sampled, they hid under leaf litter when disturbed. Because individuals were secretive and difficult to spot, sampling involved an intensive search of the forest floor. Individuals were found to be shy of torch light and upon disturbance, made quick hopping movements to hide. No individuals were found exposed during the night during either rainy or non-rainy periods. As a general observation, most sympatric anurans in the region usually emerge in the dark and call during the rain or post rain seasons. Leaf-litter dwelling and habitat distinguishes A. kurichiyana from many species of Nyctibatrachus that are torrential frogs and prefer to live in water or next to perennial streams (Biju et al., 2011). While its terrestrial habits are somewhat similar to some small-bodied Nyctibatrachus species (see Garg et al., 2017), the new lineage differs strongly from the two Lankanectes species which are aquatic (Senevirathne et al., 2018).
Distribution: All known populations of this species occur in Kurichiyarmala on the Wayanad Plateau, in the WG Escarpment (Fig. 1). The geographical range of Nyctibatrachinae, widespread across the WG, overlaps with Astrobatrachinae (Fig. 1). However, both lineages have a disjunct distribution with respect to Lankanectinae, which is restricted to the mountains of Sri Lanka (Fig. 1). The new species occurs in syntopy and in broad sympatry with Nyctibatrachus grandis, N. minimus, N. vrijeuni, and N. kempholeyensis.
Etymology: From ‘Kurichiyana,’ a local tribal community residing near the type locality and currently known geographic range of the species. Species epithet is treated as a noun in apposition to the generic name. We suggest the common English name of the Starry Dwarf Frog.
Seenapuram Palaniswamy Vijayakumar, Robert Alexander Pyron, K. P. Dinesh, Varun R. Torsekar, Achyuthan N. Srikanthan, Priyanka Swamy, Edward L. Stanley, David C. Blackburn and Kartik Shanker. 2019. A New Ancient Lineage of Frog (Anura: Nyctibatrachidae: Astrobatrachinae subfam. nov.) endemic to the Western Ghats of Peninsular India. PeerJ. 7:e6457. DOI: 10.7717/peerj.6457
Meet India's starry dwarf frog, lone member of newly discovered ancient lineage. https://www.floridamuseum.ufl.edu/science/meet-indias-starry-dwarf-frog/
