Polypedates discantus Rujirawan, Stuart & Aowphol, 2013, sp. nov.

Polypedates discantus sp. nov.

Polypedates leucomystax “Morph B” Narins, Feng, Yong and Christensen-Dalsgaard, 1998: 129. Polypedates sp. “Malay Clade” Kuraishi, Matsui, Hamidy, Belabut, Ahmad, Panha, Sudin, Yong, Jiang, Ota, Thong and Nishikawa, 2013: 1.

Holotype. ZMKU AM 0 0 992, adult male (Figs. 4 A and 5), collected at Thung Tam Sao, Hat Yai District, Songkhla Province, Thailand, N06°56’24.9’’ E100°15’15.8’’, 61 m elevation, on 15 November 2012 with advertisement calls recorded (Table 6; Fig. 3) at 18.35h at 28.4 °C by Anchalee Aowphol, Attapol Rujirawan, Siriporn Yodthong, Korkhwan Termprayoon, and Natee Ampai.

Paratypes. ZMKU AM 00990–00991, ZMKU AM 00997–01000, six adult males, same data as holotype except collected 4 February 2011, 20.20–22.00 h, at 24.0 °C by Anchalee Aowphol, Attapol Rujirawan, Wut Taksintum, Virayuth Lauhachinda, and Somphouthone Phimmachak; ZMKU AM 00993–00996, ZMKU AM 01001–01005, nine adult males, and ZMKU AM 0 1006, one adult female, same data as holotype except collected 15 November 2012, 19.05–21.00 h, at 25.0–27.5 °C by Anchalee Aowphol, Attapol Rujirawan, Siriporn Yodthong, Korkhwan Termprayoon, and Natee Ampai.

Etymology. The specific epithet discantus taken from dis L. for separate and cantus L. for song, in reference to the new species’ differing call from the syntopic P. leucomystax.

Suggested common name. Malayan slender tree frog (English). ⊿ɾɷk¶DkflnɾD: Paad-Reaw-Ma-La-Ewu (Thai), taken from Paad for tree frog, Reaw for slender, Ma-La-Ewu for Malayan.

Diagnosis. A medium-sized tree frog (SVL males 48.6–54.7 mm, female 67.5 mm) assigned to the genus Polypedates by having the head longer than broad; vomerine teeth prominent; skin of body and limbs smooth or shagreened; tips of fingers and toes dilated into large, rounded disks having circummarginal grooves; and fingers basally webbed (Liem 1970; Duellman & Trueb 1986; Brown & Alcala 1994), and by its phylogenetic placement based on molecular data (as Polypedates sp. “Malay Clade” in Kuraishi et al. 2013). The new species is similar to other members of the P. leucomystax complex, but can be distinguished by the combination of having the skin of head not co-ossified with skull; absent or indistinct white dots on the back of the thigh; presence of vocal sac opening in adult male; smooth skin in orbital region; rounded tubercle on tibiotarsal articulation; and characteristics of the male advertisement call.

Description of holotype. Adult male with SVL 49.7 mm; body slender, elongate (SVL:HW = 3.5); head triangular, longer than broad (HL:HW = 1.2); snout obtusely pointed in dorsal view, projecting beyond lower jaw, round at tip; upper eyelid width slightly greater than interorbital distance (ELW:IOD = 1.1); eyes strongly elevated; canthus rostralis distinct; loreal region oblique, slightly concave; pupil horizontal; nostril small and oval, dorsolaterally oriented, much closer to tip of snout than eye; skin of the head not co-ossified with skull; interorbital region slightly convex; tympanum distinct, separated from eye by very narrow distance; tympanum round, diameter smaller than eye (TD:EYE = 0.6); distinct supratympanic fold from eye to shoulder; pineal ocellus absent; vomerine teeth present, in two oblique groups arising on anterior medial margin of choanae, separated by a distance approximate half length of each group; choanae oval, at margins of roof of mouth; lingual papillae absent; tongue attached anteriorly, deeply notched posteriorly; oval vocal sac opening near corner of jaws.

Forelimbs slender; relative finger lengths I <II<IV <III; all fingers basally webbed; tips of all fingers with well-developed discs having circummarginal grooves, largest disk on finger III (3FDW:TD = 0.7); fingers II-IV with dermal fringes on inner and outer aspects; weak dermal fringe on outer margin of forelimb from elbow to hand; subarticular tubercles prominent, rounded, formular 1, 1, 2, 2; palmar tubercle prominent, rounded, divided; accessory palmar tubercles present; prepollex prominent, elongated oval; unpigmented nuptial pads on base of dorsal surfaces of fingers I and II.

Hindlimbs relatively long, slender; tibia similar in length to thigh length (TIL:THL = 1.0); tips of all toes with well-developed discs having circummarginal grooves, smaller than those of fingers; relative toe lengths I <II <III <V <IV; web on toe I to base of tip, on preaxial side of toe II to level of distal margin of subarticular tubercle, on postaxial side of toe II to base of tip, on preaxial side of toe III to level of distal margin of distal subarticular tubercle and continuing as a fringe to base of tip, on postaxial side of toe III to base of tip, on preaxial and postaxial sides of toe IV to level of distal margin of distal subarticular tubercle and continuing as a fringe to base of tip, and on toe V to base of tip; weak dermal fringes on outer of toes I and V; subarticular tubercles prominent, rounded, formular 1, 1, 2, 3, 2; oval inner metatarsal tubercle; outer metatarsal tubercle and supernumerary tubercles absent; rounded tubercle on tibiotarsal articulation.

Skin of dorsal surfaces of trunk and head shagreened; skin of chin and chest smooth; ventral surfaces of forelimbs and hindlimbs smooth, abdomen and ventral surfaces of thigh granular; pair of small tubercles on supracloacal opening; coarse granules and rounded tubercles around vent.

Color of holotype in life. Above yellowish-brown, below white; dark X-shaped marking weakly visible on interorbital region, neck and shoulders; scattered black blotches on back; weak dark lines running from snout to eyes; narrow dark line extending along canthus rostralis from tip of snout to eye and along supratympanic fold from eye to above shoulder; dorsal surfaces of limbs with narrow dark-cross bands; back of thigh with indistinct white spots (Fig. 6); region around anus black with white-colored tubercles; web of foot dusky; iris grey-brown with dark-brown around the pupil.

Color of holotype in preservation. Fading to light grey with dark brown markings.

Measurements of holotype. SVL 49.7, HL 17.6, HW 14.5, HD 6.6, ELW 5.6, ED 6.9, IND 3.5, IOD 5.1, SNL7.7, DNE 5.3, NS 2.3, TD 4.3, FLL 26.2, HLT 16.3, THL 26.5, AGL 24.5, TIL 26.9, FL 20.7, 3FDW 3.0, 4TDW 2.1.

Variation. Dorsal and ventral patterning is highly variable in this species. Dorsum with dark X-shaped weakly visible in ZMKU AM 00990–00991, 00993–00994, 00996–00997, 0 1002, 0 1004 and 01006; dorsum with four dark longitudinal stripes in ZMKU AM 00999–01001 and 01003; dorsum with two dark longitudinal stripes in ZMKU AM 0 0 995 and 00998; dorsum with scattered black blotches in ZMKU AM 00990–00991, 00993–00994, 00996–01000, 0 1002 and 01005–01006. Chin and anterior chest region with small dark dots in ZMKU AM 00990– 0 0 991, 00993–00996, 01000–01001, 01003–01004 and 0 1006. ZMKU AM 0 0 995 is missing the terminal phalange in left finger IV and ZMKU AM 0 0 993 has truncated right toe V. Univariate morphological variation in the type series is summarized in Table 7.

Calls of holotype. The holotype was calling from a creeping plant 0.7 m above a temporary pond. The advertisement call had three different call types: one-note, two-note and staccato calls (Fig. 3). The one-note call “ juekk ” was a single, short, one-pulsed note lasting 0.11 to 0.33 s with dominant frequency of 1.9–2.1 kHz. The two-note call “ juekk-juekk ” had two, short, one-pulsed notes lasting 1.63– 2.02 s; pulse duration of 0.14– 0.21 s; interval between pulses 1.32– 1.68 s; pulse repetition rate of 5.23–6.54 pulses per second; and dominant frequency of 2.0–2.2 kHz. The staccato call “ tok-tok-tok ….......” was a long call lasting 15.6– 20.9 s with 11–13, short onepulsed notes; pulse duration 0.05– 0.08 s; interval between pulses 1.43– 1.70 s; pulse repetition rate 5.72–6.60 pulses per second; and dominant frequency of 1.4–1.6 kHz (Table 6).

Comparisons. Polypedates discantus sp. nov. superficially resembles P. leucomystax (Gravenhorst, 1829), P. megacephalus Hallowell, 1861, P. mutus (Smith, 1940), P. braueri (Vogt, 1911), P. macrotis (Boulenger, 1891), and P. colletti (Boulenger, 1890). Polypedates discantus sp. nov. differs by having indistinct or no white spots on rear of the thigh (distinct spots or marbled pattern present in the other species); skin of head not co-ossified with skull (skin of head co-ossified with skull in P. leucomystax, P. mutus and P. megacephalus); paired vocal sac openings in adult males (absent in P. macrotis and P. mutus); no dark lateral stripe covering tympanum (present in P. macrotis); variable dorsum with X-shaped marking or two or four longitudinal stripes (distinct hour-glass figure beginning from interorbital region to sacrum in P. colletti); smooth skin in orbital region (low tubercles in P. colletti); nuptial pad on first and second fingers (only on first finger in P. colletti); and rounded tubercle on tibiotarsal articulation (conical tubercle in P. colletti; no tubercle in P. leucomystax, P. m a c ro t i s, and P. megacephalus). Size differences among P. discantus sp. nov., P. leucomystax and P. megacephalus are summarized in Table 1.

The male advertisement call of P. discantus sp. nov. differs from that of P. leucomystax, P. megacephalus and P. braueri (Table 5 and Kuraishi et al. 2011) by having 1–3 notes per call (one note in P. leucomystax and P. megacephalus); one pulse per note (10–13 pulses in P. leucomystax, 4–7 pulses in P. megacephalus and many fine pulses in P. braueri); pulse duration of 16–37 ms (4–7 ms in P. leucomystax and 6–8 ms in P. megacephalus); interpulse interval of 149–206 ms (5–9 ms in P. leucomystax, 7–9 ms in P. megacephalus); pulse repetition rate of 4–6 s -1 (79–89 s - 1 in P. leucomystax and 64–75 s - 1 in P. megacephalus); and dominant frequency of 1.7–2.3 kHz (1.1 kHz in P. braueri).

Distribution. In Thailand, the new species is known only from the type locality. Narins et al. (1998) reported it as P. leucomystax “Morph B ” from Ulu Gombak in Peninsular Malaysia (assigned to P. discantus sp. nov. on the basis of its call characteristics), and Kuraishi et al. (2013) reported it as Polypedates sp. “Malay Clade” from Hut. Lip, Kanching Selangor, Kenaboi, Negeri Sembilan, Endau Rompin, Johor, Temerloh, and Pahang, Peninsular Malaysia (assigned to P. discantus sp. nov. on the basis of its 16S rRNA gene sequence) (Fig. 7).

Ecology. The type series was collected around a temporary, road-side pond (Fig. 8). Individuals were found over-hanging the pond on vegetation and creeping plants, 0.3–1.5 m above the pond, co-existing with Microhyla berdmorei, M. heymonsi, M. fissipes, Polypedates leucomystax, P. macrotis, Rhacophorus pardalis and Humerana miopus. No foam-nests or tadpoles were found.

Data of P. braueri is from P. leucomystax (Taiwan) in Stejneger (1925)

Data of P. braueri is from P. megacephalus (Taiwan) in Matsui et al. (1986)