Litoria kikori, Richards & Oliver, 2024

Richards, Stephen J. & Oliver, Paul M., 2024, Two new species of torrent-breeding treefrogs (Anura: Pelodryadidae: Litoria) from hill forests on the southern edge of New Guinea’s Central Cordillera, Vertebrate Zoology 74, pp. 417-433 : 417-433

Litoria kikori sp. nov.

Figures 1 , 2 A, B, D, E , 3 , 4

Kikori torrent treefrog

Holotype.

SAMA R 69990 ( SJR [ JCUNQ] 3245), adult male with vocal slits and nuptial pads, calling when collected, Libano Sok , Hegigio River, Southern Highlands Province, Papua New Guinea (6.3989 ° S, 142.9761 ° E; 250 m a. s. l.), collected by Stephen Richards on 7 August 2003.

Paratypes.

SAMA R 69986 ( SJR [ JCUNQ] 3222), R 69987 ( SJR [ JCUNQ] 3240), R 69988 ( SJR [ JCUNQ] 3243), R 69989 ( SJR [ JCUNQ] 3244, R 69991 – R 69992 ( SJR [ JCUNQ] 3246–3247), QMJ 98371 ( JCUNQ [ SJR] 3241), PNGNM JCUNQ [ SJR] 3242), all males with same locality and collector details as holotype, collected between 4–7 August 2003 ; SAMA R 72336 ( SJR 14135 ), male, and R 72337 ( SJR 14141 ), female, Bifo Creek , Southern Highlands Province, Papua New Guinea (6.4483 ° S, 142.9597 ° E; 360 m a. s. l.), collected by Stephen Richards on 2 and 4 August 2014 respectively .

Diagnosis.

A species of Litoria that can be distinguished from all congeners by the following unique combination of characters: size moderate (male SVL 29.9–35.8); snout moderately long (EN / IN 0.51–0.75), slightly pointed in dorsal view, truncate in lateral view; canthus rostralis curved in dorsal view, relatively sharply defined in lateral view; limbs long (TL / SVL 0.59–0.68); finger webbing moderate, extending to distal subarticular tubercles between fingers 3 and 4; toe webbing extensive, reaching to disc or to intercalary cartilage at base of disc on all digits except toe 4; finger and toe discs moderately narrow (3 FD / SVL 0.04–0.05, 4 TD / SVL 0.04–0.05); dorsal skin finely rugose with numerous larger tubercles on exposed surfaces of torso; hindlimbs with low, crenulated dermal ridges on outer edges of tibiae and tarsi; heels with 2–3 low conical tubercles; vomerine teeth in two prominent raised clumps; vocal slits present in males; dorsal colouration mottled green and brown; hidden surfaces of shanks and groin purplish in life; and advertisement call a single loud, unpulsed musical note lasting 0.03– 0.05 s and produced at intervals of ~ 12–37 seconds for long periods.

Comparisons with other species.

We emphasize comparisons with torrent-breeding Litoria because based on taxa genetically sampled so far (e. g., Richards et al. 2021, 2023) they form a monophyletic group that is also ecologically distinctive. The new species can be distinguished from non torrent-breeding Litoria by the following combination of characters: dorsum mottled green and brown, skin tuberculate (Fig. 1 A – C ), canthus rostralis strongly curved and moderately sharply defined in dorsal view, snout-tip shallowly acuminate, webbing on fingers moderate, extending to distal subarticular tubercles on outside of fingers 2 and 3, and adult size moderate (male SVL 30–36 mm).

Litoria kikori sp. nov. can be distinguished from other torrent-breeding Litoria in New Guinea as follows: it is larger than L. amnicola Richards, Tjaturadi, Krey & Donnellan, 2021 , L. brongersmai (Loveridge, 1945) , L. lakekamu Richards & Bickford, 2023 , L. leucova ( Tyler, 1968) , L. megalops Richards & Iskandar, 2006 , L. napaea ( Tyler, 1968) , L. rara Günther & Richards, 2005 and L. rivicola Günther & Richards, 2005 (male SVL> 30 mm versus <25 mm); and further differs from L. amnicola , L. brongersmai , and L. napaea in having prominent vomerine teeth (versus indistinct, detectable only as slight bumps); from L. lakekamu and L. leucova in its green-and-brown-mottled dorsum (versus green); from L. megalops in having moderate finger webbing (versus absent), and in its smaller eye (EYE / SVL 0.12–0.14 versus 0.14–0.17); and from both L. rara and L. rivicola by its longer hindlimbs (TL / SVL> 0.59 versus <0.56) and green or brown dorsal colouration (versus predominantly grey or greyish brown). Litoria kikori sp. nov. is substantially smaller than L. angiana (Boulenger, 1915) (max male SVL <40 mm versus> 50 mm), and further differs in having the snout distinctly acuminate (versus relatively blunt) in dorsal aspect, canthus rostralis curved in dorsal view (versus straight), and dorsum and lateral edge of tarsus strongly tuberculate in life (versus relatively smooth).

Litoria kikori sp. nov. differs from the following ten similar-sized or slightly larger torrent-breeding species – L. arfakiana (Peters & Doria, 1878) , L. becki (Loveridge, 1945) , L. bulmeri ( Tyler, 1968) , L. oenicolen Menzies & Zweifel, 1974 , L. fuscula Oliver & Richards, 2007 , L. macki Richards, 2001 , L. micromembrana (Tyler, 1963) , L. modica ( Tyler, 1968) , L. spinifera ( Tyler, 1968) and L. wollastoni (Boulenger, 1914) – in having moderately extensive finger webbing that extends to distal subarticular tubercle on fingers 2, 3, and 4 (versus at most basal webbing between fingers 3 and 4); and further differs from L. arfakiana , L. oenicolen , L. spinifera and L. wollastoni in its less sharply acuminate snout tip and lacking prominent spiniform tubercles on heel (and in L. spinifera across body); from L. becki in its extensively webbed toes (versus toes half-webbed); from L. bulmeri by lacking a dark brown to black lateral band on head and body (versus present); from L. fuscula in having prominent vomerine teeth (versus indistinct, detectable only as slight bumps), green and / or brown mottled dorsal colouration (versus dark brown with no obvious pattern), and in having small conical tubercles along heel (versus no tubercles); and from L. macki in having low, indistinct tubercles on eyelids (versus prominent and large) and dark purplish-brown colouration in groin (versus yellow).

Litoria kikori sp. nov. can be distinguished from four similar-sized species with moderate webbing between the fingers as follows: from L. dorsivena ( Tyler, 1968) and L. hastula Oliver, Iskandar & Richards, 2023 by its green-and-brown mottled dorsal colouration (versus predominantly brown) and snout relatively rounded in lateral view (versus distinctly acuminate in both lateral and dorsal views); from L. pratti (Boulenger, 1911) by its curved canthus rostralis (versus straight) and slightly longer limbs (TL / SVL> 0.59 versus <0.57); and from L. scabra Günther & Richards, 2005 by its longer limbs (TL / SVL> 0.59 versus <0.56), hindlimbs with series of low lateral tubercles (versus a crenulated ridge), and green or green-and-brown mottled dorsal colouration (versus predominantly grey or greyish brown) ( Günther and Richards 2005).

Litoria kikori sp. nov. is most similar to L. spartacus Richards & Oliver, 2006 (Fig. 2 A ) and is closely related to it (see below), but can be differentiated by its smaller size (male SVL 29.9–35.8 versus 35.6–37.4, female SVL 45.4 versus 51.1), narrower finger pads (3 FD / SVL 0.045 –0.052 versus 0.048 –0.062), narrower toepads (4 TD / SVL 0.037 –0.050 versus 0.052 –0.062) (Fig. 2 B ), distal subarticular tubercle of finger 4 wider than long and slightly bifid (versus roughly equal in width and length and not bifid) (Fig. 2 B ), groin in life unpigmented or light purplish (versus orange) (Fig. 2 C – E ), throat in males without brown mottling (versus typically with brown mottling) and call consisting of a single note repeated at 12–37 second intervals for at least several minutes (versus multiple notes in short series lasting 5–20 seconds; Richards and Oliver 2006).

Description of holotype.

Adult male with vocal slits and indistinct pale-brown nuptial pads with fine asperities. Habitus moderately slender, limbs long (TL / SVL 0.67), head wide (HW / SVL 0.36). Snout protruding distinctly beyond lower jaw, rounded in lateral view, moderately acuminate in dorsal view (Fig. 3 A, B ). Canthus rostralis with rounded edge, but clearly defined in both dorsal and lateral view and curved in dorsal view; loreal region steeply sloping, slightly concave. Nostrils near top of snout, oriented laterally, not visible in dorsal view. Vomeropalatines forming two prominent elevations, each with 3–4 teeth positioned midway between choanae. Tongue small, nearly round, with prominent posterior notch; vocal slits laterally in floor of mouth, extending from near angle of jaws about one half distance to front of jaw. Eyes large (EYE / SVL 0.14), prominent, protruding in dorsal and ventral views; pupil horizontal, pigmentation on nictitating membrane restricted to very thin narrow band of maculations along dorsal edge. Tympanum moderately small (TYM / SVL 0.05), one-third diameter of eye (TYM / EYE 0.32), tympanic annulus clearly defined, except dorsal edge obscured by thick, slightly curved supratympanic ridge.

Skin on dorsal surfaces of torso and head rugose, with numerous large, rounded tubercles (Fig. 3 A ), skin on throat finely granular, on abdomen coarsely granular. Forelimbs finely tuberculate on exposed surfaces, with scattered tubercles on ventral surface, and distinct ventrolateral fold along outer edge of forearm. Hindlimbs tuberculate on exposed dorsal surfaces of tibia and tarsus, outer edge of tibia and tarsus with series of tubercles (Fig. 3 C ), heel with three low white tubercles. Ventral surfaces of thighs coarsely granular proximally, becoming less so distally, ventral surfaces of tarsus and tibia smooth.

Fingers long, relative lengths 3> 4> 2> 1. All fingers webbed (Fig. 3 D ), in thin strip between fingers 1–2, and extending to distal subarticular tubercles on outside of fingers 2 and 3, and inside of finger 4 (Figs 2 B , 3 D ). Tips of all digits expanded into prominent discs (3 FD / 3 FP 1.6) with circum-marginal grooves. Subarticular tubercles rounded or bifid, distal tubercles of fingers 3 and 4 most notably bifid (Fig. 3 D ); outer metacarpal tubercles ovoid, indistinct; inner metacarpal tubercle prominent, visible as lunate lateral extension from base of finger 1 in both ventral and dorsal view. Nuptial rugosity on outer metacarpal tubercle finely granular, indistinct.

Toes long, relative lengths 4> 3> 5> 2> 1, all webbed (Fig. 3 E ); web reaching to terminal disc or to intercalary cartilage at base of disc on toes 1, 2, 3 and 5 and to distal subarticular tubercle on both sides of toe 4. Discs prominent (4 TD / 4 TP 1.6), with supramarginal grooves. Subarticular tubercles prominent, rounded or slightly bifid (Fig. 3 E ); inner metatarsal tubercle indistinct and ovoid, outer metatarsal tubercle slightly smaller, indistinct and rounded.

Colour in preservative.

Dorsal surfaces predominately dark blueish green with small areas of dark brown (Fig. 3 A ); lateral surface of snout predominately brown, with diffuse blueish green blotch extending anteriorly from lower edge of eye; prominent brown blotch below supratympanic fold; labial region with numerous small white spots; upper lips and region around rictus of jaws white (Fig. 3 B ). Ventral surfaces largely off white, with some tiny brown maculations along edge of jaw. Dorsal surfaces of arms and legs predominately greenish brown, towards extremities brown colouration becomes more diffuse and off-white ground colouration becomes more visible. Most ventral surfaces of limbs largely off white with scattered patches of brown, particularly on hands, lateral edge of arms and femur; tarsi and feet (including webbing) off white, heavily spotted with brown.

Variation.

Measurements and proportions of males in the type series are similar (Table 1 ) and all paratypes have similar webbing on the hands and feet. Dorsal colour pattern is variable, ranging from bluish green heavily mottled with dark brown, through to predominantly greyish-brown with a small amount of blueish-green splotching. Ventral colouration is consistently off white to buff, with only slight variation in the extent of light-brown mottling on the legs and along the sides of the torso. The single female is substantially larger than the males in the type series (Table 1 ) and has more extensive greyish-brown mottling on the ventral surfaces but is otherwise similar in colouration and proportions.

Colour in life.

The following description of colouration in life is based on photographs of three specimens (Figs 1 A – C , 2 D, E ). Dorsal surfaces of torso, snout, forelimbs and most exposed surfaces of hindlimbs mottled with medium brown and bright green, with relative extent and dominance of green and brown areas showing considerable variation across specimens. Exposed surfaces of thigh light brown without green pattern. Tympanum always brown. Posterior edge of upper jaw usually with at least some small off-white blotches. Lateral surfaces of body sometimes with large ragged-edged silvery-yellow blotches. Where portions of venter are visible in photos (2 D) they are translucent, but heavily overlaid with white spots and brown maculations. Hidden posterior edge of thighs, shanks and inguinal region purplish. Tubercles around vent white. Iris silver with thin dark-brown vermiculations.

Advertisement call.

We recorded 13 calls from four individuals. Calls were similar among all individuals and were combined for analysis. The call of Litoria kikori sp. nov. is a single loud, musical note, sounding like ‘ tink’, uttered from leaves and branches between 2 and> 5 m above the banks of large foothill streams. Calls are 0.03– 0.05 s long (mean = 0.04, SD = 0.008, n = 13); notes are not pulsed, but two notes are partially divided into two subpulses. Frequency is concentrated in two bands, one at about 3600 Hz and the other at 1800 Hz (Fig. 4 ). The higher band is dominant in 11 calls (3460–3660 Hz, mean = 3600, SD = 58.32) while the lower frequency was dominant in two calls produced by SAMA R 69992 . Calls were produced at 0.38–37.0 seconds. However, if a single rapidly repeated couplet produced by SAMA R 69991 (0.38 s interval) is excluded then inter-call interval is 11.9–37.0 seconds (mean = 17.8, SD = 8.0 s, n = 8). Males produced these single-note calls in bouts lasting for at least several minutes. An exemplar call from paratype SAMA R 72336 has been uploaded to iNaturalist (https://www.inaturalist.org/observations/218063325).

Molecular differentiation.

Genetic divergences (p-distances) between Litoria kikori sp. nov. and its closest relative L. spartacus were between 0.135 –0.146 (based on comparisons of 654 bp of mitochondrial ND 4 gene data).

Etymology.

Named in reference to the Kikori River basin to highlight the remarkable frog diversity and broader conservation significance of this region. Used as a noun in apposition.

Distribution and ecological notes.

Known only from two locations, Libano Sok and Bifo Creek, located 6 km apart in the Kikori River basin along the southern slopes of the Central Cordillera of Papua New Guinea (Fig. 5 ).

Males in the type series were calling from leaves between 2–4 metres above swift-flowing rivers in hill forest (Fig. 6 A ). The female paratype ( SAMA R 72337 ) was collected from a tree adjacent to Bifo Creek. Five large, yellow eggs measured in situ were 1.7–2.0 mm diameter in diameter. At Libano Sok Litoria kikori sp. nov. occurred in sympatry with one other torrent-breeding pelodryadid frog, the new species described below. No other torrent-dwelling Litoria were detected at Bifo Creek.

Suggested IUCN redlist status.

Litoria kikori sp. nov. is known only from two sites approximately six kilometres apart. However, there are large areas of forest in the region, which is sparsely inhabited. Furthermore, it occurs at elevations at which ecologically similar torrent-breeding Litoria in tropical Australia have been able to persist in the presence of the frog pathogen B. dendrobatidis . Despite its small range, and uncertainty about the species’ ability to persist if intensive logging occurs, we suggest that this species should be considered Least Concern at this stage. However, we stress that further surveys are needed to better document this species’ distribution and the extent to which it overlaps with areas of forest loss.

Figures

Figure 1. In-life images of Litoria kikori sp. nov.: A adult female paratype (SAMA R 72337) from Bifo Creek, Papua New Guinea; B adult male paratype (SAMA R 72336) from Bifo Creek, Papua New Guinea; C adult male, unvouchered specimen from Libano Sok, Papua New Guinea. All photographs by Stephen Richards.

Figure 2. Detailed comparisons of Litoria kikori sp. nov. and L. spartacus: A dorsal views of L. spartacus (top) and L. kikori sp. nov. (bottom) holotypes; B comparisons of underside of fingers, showing wider discs and rounded subarticular tubercle on finger 4 in holotype of L. spartacus (left) versus narrower pads and bilobed tubercle on finger 4 on holotype of L. kikori sp. nov. (right); C orange groin and lower shanks of L. spartacus from Moro, Papua New Guinea; and unpigmented or, at most, slightly purplish groin and shanks on L. kikori sp. nov.; D holotype; E paratype SAMA R 72337. All photographs by Stephen Richards.

Figure 3. Details of the holotype (SAMA R 69990) of Litoria kikori sp. nov.: A dorsal view of head; B lateral view of head; C dorsal view of hindlimbs and dorsolateral view of hidden surfaces of thighs; D hand; E foot. Scale bar = 5 mm.

Figure 4. A waveform, B power spectrum and C spectrogram of a single call of Litoria kikori sp. nov. (SAMA R 69990) recorded at an air temperature of 24.5 ° C.

Figure 5. Distributions of Litoria kikori sp. nov. (white circle), L. spartacus (blue squares) and L. grinpela sp. nov. (black circle, type locality). The black and white circle is Libano Sok where both new species occur in sympatry. Libano Sok is the type locality of Litoria kikori sp. nov.

Figure 6. A Streamside habitat of Litoria kikori sp. nov. in foothill forest at Bifo Creek, Southern Highlands Province, Papua New Guinea; B habitat of L. grinpela sp. nov at the type locality along the Liddell River, Western Province, Papua New Guinea; C a waterfall emerging out of the ground just upstream from image B. This is the lowest known locality (215 m a. s. l.) for three other stream-breeding pelodrydadid treefrog species: L. arfakiana, L. spartacus and Nyctimystes pulcher.