Contributions to Zoology, 83 (4) – 2014S.D. Biju; Sonali Garg; Stephen Mahony; Nayana Wijayathilaka; Gayani Senevirathne; Madhava Meegaskumbura: DNA barcoding, phylogeny and systematics of Golden-backed frogs (Hylarana, Ranidae) of the Western Ghats-Sri Lanka biodiversity hotspot, with the description of seven new species

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Hylarana temporalis (Günther, 1864)

Günther's Golden-backed frog

(Figs 17d-i, 18d-l, 19c-f, 20; Tables 1-2)

Original name and description. Hylorana temporalis Günther, 1864. The Reptiles of British India, Ray Society by Hardwicke, 427. Lectotype. By present designation, NHM 1947.2.2.5, an adult female, SVL 76.5 mm, collected by Mr Cumings. Type locality. ‘Ceylon’ (= Sri Lanka). Current status of specific name. Valid name, as Hylarana temporalis (Günther, 1864).

Referred specimens. NHM 1947.2.29.47 and NHM 1947.2.2.6, two adult males, ‘Ceylon’, collected by Mr Cumings; NHM 1947.2.29.46 (ex BMNH, an adult female, ‘Ceylon’, collected by Mr Cumings; DZ 1092-1094, three adult males, DZ 1095, an adult female, Hemmathagama, Kegalle dist., collected by MM and others, 19 February 2013; DZ 1141-1142, two adult males, Kudawa, Sinharaja, Ratnapura dist., collected by MM and NW, 20 March 2013; DZ 1150-1152, three adult males, Udadumbara, Kandy dist., collected by MM and others, 18 February 2013; DZ 1046, an adult male, DZ 1047, an adult female, Kevunkahata Ela, Peradeniya, Kandy dist., collected by MM and others, 17 February 2013; DZ 1246, an adult male, DZ 1197, DZ 1240-1242, four adult females, Sarasavi Oya, Peradeniya, Kandy dist., collected by MM and others, 26 April 2013; DZ 1153, an adult male, Panwila, Kandy dist., collected by MM and others, 18 February 2013; DZ 1116, a sub-adult, Kithulgala, Kegalle dist., collected by MM and others, 4 March 2013.

Comments. The original description does not mention the number of specimens in the type series (Günther, 1864). The present study found seven specimens, which we regard as syntypes, BMNH, BMNH, BMNH, BMNH 58.10.15 and BMNH 58.10.18, in the Natural History Museum, London, from ‘Ceylon’ (= Sri Lanka), collected by Cumings. Dutta (1997) lists nine specimens, whereas Dutta and Manamendra-Arachchi (1996) list six, both citing these aforementioned museum numbers with punctuation errors. In order to stabilize the nomenclatural status of this species, we designate one of the syntypes as the lectotype. Since no specimen was specifically described in more detail in the original description, we chose an adult female as the lectotype.

There was further confusion with regards to the specimen number of the lectotypified syntype, since the specimen numbers of syntypes differ between the specimen tags, jar labels and NHM register information. The specimen number according to the specimen tag is NHM 1947.2.3.5, however the jar label states NHM 1947.2.2.5 (ex BMNH The museum register provides no resolution to the incongruences of numbers, by providing only the former number BMNH, which again differs from that provided on the specimen jar. The present study follows the specimen number on the specimen tag, since it is considered here to be more reliable.

Comparison. Hylarana temporalis could not be confused with Hylarana serendipi sp. nov., the only species of the Hylarana temporalis group to which it is closely related, due to its larger adult size (Figs 17a, d, g). See H. serendipi for comparison with that species. Hylarana temporalis has long been believed to occur throughout the Western Ghats of India and Sri Lanka (see ‘Remarks’ section) due to misidentifications of other species. However, H. temporalis differs from all the members of the Western Ghats by the presence of a rather distinct supratympanic ridge (vs. absent on all the Western Ghats species) (Figs 17f, i, 19c-f).

Genetic divergence. Intraspecific genetic variation within populations of Hylarana temporalis was 0.1 ± 0.1% (range 0-0.2%, N = 7) for 16S, 0.3 ± 0.2% (range 0-0.7%, N = 9) for COI and 0.5 ± 0.4% (range 0-1.3%, N = 10) for Cytb. Based on phylogenetic position, H. temporalis is closely related only to H. serendipi (Fig. 4). See H. serendipi for comparison with that species. Since H. temporalis was believed to occur throughout western India and Sri Lanka, the present study compared H. temporalis with H. montanus, its closest relative from India based on phylogenetic position, and found a very high genetic divergence of 11.7 ± 0.1% (range 11.5-11.9%, N = 42) for 16S, 20.2 ± 0.3% (range 19.7-20.9%, N = 54) for COI and 22.8 ± 0.4% (range 22.1-24.2%, N = 72) for Cytb (Tables S2-S3).

Description of lectotype (Figs 17d-f, 18d-f). Medium-sized, robust species, adult female (SVL 76.1). Head moderately large (HW 26.2, HL 28.7, IFE 13.5, IBE 19.7), longer than wide, flat above; snout oval from dorsal view, square (due to poor preservation) from lateral view, slightly protruding, its length (SL 11.6) longer than horizontal diameter of eye (EL 9.8); loreal region acute and concave with angular canthus rostralis; interorbital space flat, wider (IUE 6.9) than upper eyelid (UEW 5.9) and narrower than internarial distance (IN 7.6); nostril oval with flap of skin laterally, closer to tip of snout (NS 5.1) than eye (EN 6.5); tympanum (TYD 6.5) 66% of eye diameter (EL 9.8); tympanum-eye distance (TYE 2.8); pineal ocellus absent; vomerine ridge present, bearing numerous small teeth, with an angle of 45° to body axis, as close to choanae as to each other, longer than distance between them; tongue large, emarginated, bearing no median lingual process. Forelimbs moderately long and thin; forelimb (FAL 15.8) shorter than hand length (HAL 19.7); fingers rounded without lateral fringes, finger length formula II<I<IV<III, finger tips dorsoventrally compressed with obtusely pointed discs and lateroventral groove, moderately wide compared to finger width (FDI 2.0, FWI 1.2; FDII 1.4, FWII 1.2; FDIII 1.8, FWIII 1.3; FDIV 1.9, FWIV 1.2); subarticular tubercles very prominent, oval, single, all present; prepollex distinct, oval, two oval distinct palmar tubercles; a distinct supernumerary tubercle on base of each finger. Hindlimbs relatively long and thin; thigh length (TL 38.6) shorter than shank (SHL 40.5), and longer than foot (FOL 37.3); relative digit lengths I<II<III=V<IV; toe tips dorsoventrally compressed with nearly pointed discs and lateroventral grooves, rather wide compared to toe width (TDI 2.0, TWI 1.2; TDII 2.2, TWII 1.2; TDIII 2.3, TWIII 1.2; TDIV 2.2, TWIV 1.2; TDV 2.1, TWV 1.2); webbing moderate: I1-2II1-2III1-2+IV2-1V; dermal ridge along toe V absent; subarticular tubercles prominent, oval, all present; inner metatarsal tubercles ovoid and short; outer metatarsal tubercles rounded, prominent; supernumerary tubercles absent; tarsal tubercles absent.

Skin of dorsal and lateral surfaces of head, anterior part of back, limbs and ventral surfaces smooth; posterior dorsum, flanks and ventral thighs weakly granular; dorsolateral folds that extend from the posterior corner of the eye to the entire body length on both sides weakly prominent; supratympanic ridge present (Fig. 17f); rictal gland present at the corner of the mouth; moderately small gland above the insertion of the forelimb, humeral glands absent.

Colour in preservation (Figs 17d-f). Dorsal surface greyish-brown; lower flanks light grey; tympanic area light grey, tympanum brown; upper lip with grey stripe continuing through rictal gland to above arm insertion; dorsolateral folds dark grey; forelimbs, dorsal parts of thigh, tibia and foot light brown, anterior part of thigh light brown with grey patches, cross-bands are weakly formed; throat and margin of throat light brown colored; chest and belly light brown; ventral parts of thigh and tibia light grey; foot and webbing light grey. Colour in life (DZ 1046) (Fig. 19d). Dorsal surface light brown with large greenish-brown patches; lower flanks light brown; tympanic area brown; upper lip with yellowish-white stripe continuing through rictal gland to above arm insertion; forelimbs, dorsal parts of thigh, tibia and foot light brown with grey spots, dark grey cross-bands; throat and margin of throat white with black flecks; chest and belly off-white; ventral parts of thigh, tibia and foot greyish-white with black spots; webbing dark grey with minute specks; iris lower half dark brown and upper half golden brown.

Variation. See Table 2 for morphometric data from 13 adult males and eight adult females. Considerable variation in life also reflected in preserved specimens. DZ 1092: dorsum light reddish-brown with irregular light grey and light brown spots, a distinct dark brown stripe from tip of snout to anterior corner of eye, chest and throat light brown with yellowish-brown marbling in life (Fig. 19c), dorsum turned grey in preservation; DZ 1153 and DZ 1151: dorsum light golden brown with light brown spots in life (Figs 19e-f), turned greyish-brown in preservation; DZ 1197: dorsum dark brown, throat, chest and belly grey in preservation; DZ 1242 and DZ 1047: dorsum brown, throat, chest and belly light brown with grey marbling in preservation.

Secondary sexual characters. Male: Single oval shaped nuptial pad on finger I present, cream-coloured; two vocal sacs faintly visible externally on the posterior lateral side of the throat; humeral glands weakly developed, positioned laterally on the preaxial side of the upper forelimb. Female (DZ 1047): ova white, pigmented on pole (diameter 1.3-1.7 mm, N = 20).

Distribution. This species is known only from Sri Lanka, at elevations between 40-1850 m asl. We observed this species from Kandy dist. (Kevunkahata Ela, Peradeniya; Sarasavi Oya, Peradeniya; Panwila, Wattegama; Udadumbara, Hunnasgiriya), Kegalle dist. (Kithulgala and Hemmathagama), Nuwara Eliya dist. (Morey estate, Sri Pada [Adam’s Peak]), and Ratnapura dist. (Kudawa, Sinharaja) (Fig. 20, Table 1).

Habitat and natural history. This species was studied from various habitats ranging from highly disturbed lowland wayside streams, to evergreen primary forest on mountains. Two individuals were collected from emergent boulders in a forest stream. When approached they immediately jumped into the water and were observed to remain under water for about 10 min. The breeding season starts from August-May, when males were found calling from 18:00-23:00 h, however, individuals of this species were not found in streams during the mid-monsoon when rains are heaviest. Hylarana temporalis prefers rocky boulder strewn streams, either forested or non-forested. It is not found in marshy areas under forest cover, which at Sinharaja World Heritage Site was occupied by Hylarana serendipi. Egg clutches consisting of 800-1200 slightly green coloured eggs were found in peripheral rocky pools along these stream. Tadpoles have mouths situated ventroterminally, and are found both in the main streams and rocky pools.

Remarks. This species was also often misidentified. It was originally described from Sri Lanka and frequently reported from the Indian mainland (e.g. Boulenger, 1920; Inger et al., 1985; Daniel and Sekar, 1989; Dutta and Manamendra-Arachchi, 1996; Dutta, 1997; Chanda, 2002; Daniels, 2005; Reshmy et al., 2010, 2011). Biju (2001) raised doubts about the identity of Indian populations, discussed the large amount of intraspecific variations, and suggested a revision of the species. Our study presents strong phylogenetic and morphological support confirming that this taxon is endemic to Sri Lanka and resolves a long standing taxonomic confusion.

Hylarana malabarica group. This group can be distinguished from other peninsular Indian-Sri Lankan Hylarana groups, by the following suite of characters: medium-sized adult (male, SVL 44-70 mm; female, SVL 47-70 mm) body slender to robust; dorsolateral folds moderately or well developed (Fig. 5); finger discs without lateroventral grooves and tips rounded (Fig. 6); fourth toe webbing does not extend beyond the second subarticular tubercle on either side; distinct rictal gland posterior to corner of mouth; tympanic area dark brownish-black; groin reticulated light grey or dark brown, with yellow or grey patches. In a phylogenetic framework, Hylarana malabarica group can be characterised as the most basal clade of all other members of the Western Ghats + Sri Lanka Hylarana radiation. The Hylarana malabarica group contains one Sri Lankan and one radiation from the Western Ghats (H. gracilis + H. malabarica), but none of the other Indian and Sri Lankan radiations (Fig. 4).