Litoria lisae, Richards & Donnellan & Oliver, 2023

Richards, Stephen J., Donnellan, Stephen C. & Oliver, Paul M., 2023, Five new species of the pelodryadid genus Litoria Tschudi from the southern versant of Papua New Guinea’s Central Cordillera, with observations on the diversification of reproductive strategies in Melanesian treefrogs, Zootaxa 5263 (2), pp. 151-190 : 170-175

Litoria lisae , sp. nov.

Lisa’s Treefrog

Figs 11–13

https://zoobank.org/ urn:lsid:zoobank.org:act:C64BD388-84E0-4288-A6CD-F70DFEABDC35

Holotype. SAMA R71689 ( FN SJR15385 ), Arakubi Quarry , Southern Highlands Province, Papua New Guinea (6.4619°S, 143.2560°E; 1030 m a.s.l.) by S.J. Richards on 16 May 2017.

Paratypes. (n = 8, all adult males) SAMA R71688 ( SJR14931 ), same details as holotype but collected on 1 July 2015 ; R71690 ( FN SJR15388 ), Kilometer Point 107, Iagifu Ridge, Southern Highlands Province, Papua New Guinea (6.4402°S, 143.2240°E; 1,400 m a.s.l.) by C. Dahl and S.J. Richards on 17 May 2015 ; R60719–60720 ( FN SJR2381–2382 ) and R71686 ( FN SJR2127 ), summit of Iagifu Ridge , Southern Highlands Province, Papua New Guinea (6.4446°S, 143.2193°E; 1360 m a.s.l.) by S.J. Richards on 23 October 2001 ( R60719–60720 ) and 27 May 2002 respectively; R60716 ( FN SJR2443 ), R71687 ( FN SJR2445 ) and PNGNM ( FN SJR2444 ), Gobe Ridge summit, Southern Highlands Province, Papua New Guinea (6.8145°S, 143.7743°E; 830 m a.s.l.) by S. Richards on 29 October 2001 .

Diagnosis. Litoria lisae sp. nov. is distinguished from all other Litoria by the following unique combination of characters: size small (SVL of males 27.0– 29.7 mm); dorsum in life green with darker green spots; vomerine teeth absent; finger webbing extensive; prominent dermal fold along outer edge of foot; pigmentation on nictitating membrane restricted to narrow band at dorsal margin; advertisement call a single note containing either evenly spaced or discretely clumped pulses; and is genetically diagnosable from L. haematogaster sp. nov. at 65 sites and from L. majikthise at 64 sites in the 787 base pair alignment of mitochondrial ND4 gene and flanking tRNA ( Table 1 ).

Description of holotype. Adult male ( Fig. 11A ) with vocal slits and pale brown nuptial pads. Morphometric data are summarised in Table 4 . Body very slender. Limbs long (TL/SVL 0.56). Head narrower than long (HW/SVL 0.28; HL/SV 0.33, HW/HL 0.87). Vomerine teeth absent. Tongue moderately large, oval, with broad posterior notch. Vocal slits short, located laterally in floor of mouth, extending from slightly posterior of angle of jaws to slightly anterior of angle of jaws. Snout narrowly rounded in dorsal view ( Fig. 12A ), bluntly rounded (nearly truncate) in lateral view ( Fig. 12B ); canthus rostralis broadly rounded, nearly straight; loreal region steep, slightly concave; lips slightly flared; nostrils much closer to tip of snout than eyes, oriented anterolaterally; internarial distance equal to distance from external naris to eye (EN/IN 1.0); eyes moderately small (EYE/SVL 0.11) but prominent, protruding in dorsal and ventral views; pupil horizontal, pigmentation on nictitating membrane restricted to narrow band along dorsal edge. Tympanum small (TYM/SVL 0.05), slightly less than one half diameter of eye (TYM/EYE = 0.45), distinct except dorsal edge of annulus obscured by thick, strongly curved supratympanic ridge.

Skin of dorsum and dorsal surfaces of limbs very finely granular ( Fig. 11A ). Ventrally throat, chest and abdomen coarsely granular; ventral surfaces of limbs with scattered low tubercles, most prominent on posteroventral margins of thighs. Broken white dermal ridge below vent not extending onto adjacent regions of upper thighs; clump of ~15 prominent white tubercles below dermal ridge; heels with five (right) and seven (left) low, white tubercles; outer edge of foot with series of low, pale tubercles extending from heel nearly to distal subarticular tubercle of Toe 5, those on right tarsus partially fused to form short (3.5 mm) ridge; outer edge of hand with row of small pale tubercles extending from mid-point along forearm to distal subarticular tubercle on Finger 4.

Fingers moderately short with expanded terminal discs (3FD/SVL 0.05; 3FD/3FP 1.88) with distinct marginal grooves; subarticular tubercles strongly bilobed; relative lengths of fingers: 3>4>2>1 ( Fig. 12C ). Webbing on inside of Finger 4 reaching to just above distal subarticular tubercle, on outside of Finger 3 reaching to top of distal subarticular tubercle and continuing to disc as thick flange ( Fig. 12C ), on inside of Finger 3 reaching to small proximal subarticular tubercle, on outside of Finger 2 reaching to halfway between distal subarticular tubercle and disc, and between fingers 1 and 2 limited to basal fringe. Hand with well-defined narrow inner, and less well defined but detectable outer, metacarpal tubercles. Nuptial pad on Finger 1 pale brown, elongate (1.5 mm long), broader distally than proximally. Toes with expanded terminal discs with terminal grooves, smaller than those on fingers (4TD/SVL 0.04, 3FD/4TD 1.25) ( Fig. 12D ); relative lengths: 4>5=3>2>1. Webbing on inside of Toe 5 reaches nearly to disc, on both sides of Toe 4 to base of distal subarticular tubercle, on outside of Toe 3 nearly to base of disc, on inside of Toe 3 to halfway between proximal and distal subarticular tubercles, on outside of Toe 2 to slightly more than halfway to distal subarticular tubercle, and between toes 1 and 2 reduced to a basal fringe. Foot with welldefined oval inner metatarsal tubercle, poorly defined outer tubercle ( Fig. 12D ).

Colour in life ( Fig. 11A ). Dorsal surfaces lime green becoming yellow green laterally and on dorsal surfaces of limbs, green on forelimbs terminating sharply at wrists; dorsal and lateral surfaces with scattered darker green spots; white to yellowish-white bar extends from beneath eye posteriorly to base of forearm; white mid-lateral stripe extends from approximately midway between front and hind limbs to groin; ventrally white anteriorly, except broad pale-brown band around edges of throat, extending onto proximal portions of forelimbs; abdomen yellow posterolaterally and in hidden surfaces of limbs and axillae, yellow in axillae extending approximately halfway along posterior surfaces of forearms; enlarged tubercles on outer edges of limbs and around vent white. Dorsal surfaces of hands and feet stippled with brown spots and blotches, patches of yellowish green dorsally on fingers 3 and 4. Iris ivory with paler ivory rim around pupil and dense dark brown reticulations.

Colour in preservative. In preservative dorsal and lateral surfaces mottled darker and lighter blue, brown pigment on throat prominent, much darker than in life; patch of brown pigment midlaterally that was nearly undetectable in life now evident; yellow of posteroventral surfaces and limbs now creamy, pale bar under eye white, more prominent than in life; throat and abdomen creamy with white tubercles.

Variation. All of the paratypes are adult males. Morphometric variation is limited ( Table 4 ) but snout shape is variable –the holotype has the most narrowly rounded snout of the type series – in most specimens the tip of the snout is bluntly rounded or in two specimens (SAMA R60716, R71690) near-truncate. All specimens exhibit the distinct white bar beneath the eyes, and in life are yellow on the hidden surfaces of the legs and have extensive areas of yellow on the posterior surfaces of the abdomen ( Fig. 11C ). However, dorsal and lateral colour in life is highly variable with some specimens being much darker green than the holotype, or with more prominent darker green spots and large brown patches dorsally or laterally (e.g., SAMA R71690, Fig. 11B ). In preservative types range from pale to dark blue with scattered darker flecks and blotches dorsally; intensity of dark-brown pigmentation on throat is also variable, ranging from pale brown clumps of pigmentation in SAMA R71686, to intense dark brown band of pigmentation laterally on the throat in the holotype and SAMA R71690.

Advertisement call. We recorded 17 calls produced by the holotype at an air temperature of 22.0°C and 13 calls produced by SAMA R71688 at an air temperature of 20.5° C. Calls of both animals were similar so data were combined for analysis but, where relevant, differences are noted. Litoria lisae sp. nov. produces two distinct call types ( Fig. 13 ) at highly variable intervals (inter call interval 0.42– 31.22 s; mean = 6.55 s, SD = 7.22, n = 27), and there appeared to be no pattern to the sequence in which the two call types were produced. Each call type is a single, short note but the rate and pattern of pulse production within notes differ markedly. The first call type is a short ‘buzz’ comprising a rapidly repeated series of evenly spaced pulses, with approximately 0.006 –0.009 s between pulses, while the second call type is a more slowly repeated series of pulses which are ‘clumped’ into discrete groups of 2–3 ( Fig. 13 ) with approximately 0.004 s between pulses within groups and 0.03 s between discrete pulse groups. Although the total length of both call types overlaps extensively the first call type contains more pulses that are produced at a faster rate. We here refer to call type 1 as buzz calls, and call type 2 as chirp calls; they are each described in more detail below.

Eleven buzz calls from both animals combined were 0.12– 2.34 s long (mean 0.18, SD 0.03) and contained 10– 22 pulses (mean 16.36, SD 3.69) produced at a rate of 72.3–103.9 pulses/s (mean 87.62, SD 10.53). Although the structure of buzz calls produced by the holotype and SAMA R71688 was extremely similar, the three buzz calls of SAMA R71688 were generally shorter (0.13– 0.17 s vs. 0.16– 0.24 s) and contained fewer pulses (10–13 vs. 16–22) produced at a slower rate (72.29–74.38 vs. 83.76–103.89 pulses/s) than eight buzz calls produced by the holotype.

Nineteen chirp calls from both animals combined were 0.11– 0.17 s long (mean 0.15, SD 0.02) and contained 6–12 pulses (mean 8.68, SD 1.82) produced at a rate of 37.26–69.56 pulses/s (mean 52.58, SD 9.71). Again, the structure of chirp calls produced by the holotype and SAMA R71688 was extremely similar and there was extensive overlap in call length between the 10 chirp calls produced by SAMA R71688 (0.107 –0.166 s) and the holotype (0.118 –0.176 s). However, chirp calls of SAMA R71688 contained fewer pulses (6–8 vs. 9–12) produced at a slower rate (37.26–55.04 vs. 52.63–69.56 pulses/s) than the holotype. Whether these call types serve different acoustic functions is not known.

Comparisons. In its moderate size (male SVL 27.0– 29.7 mm), slender body, green and brown dorsal colour, extensively webbed fingers, and males lacking a rostral spike, Litoria lisae sp. nov. most closely resembles the following 11 species: L. aplini , L. daraiensis sp. nov., L. gracilis , L. haematogaster sp. nov., L. iris , L. majikthise , L. nigropunctata , L. richardsi , L. singadanae , L. umarensis and L. verae . Litoria lisae sp. nov. is also morphologically similar to the new species described below and is compared with it in that species’ account.

Litoria lisae sp. nov. can be distinguished from L. aplini by its smaller body size (adult males 27.0– 29.7 mm vs. males 31.9–35.1 mm SVL), less prominent dermal fold along outer edges of limbs, hidden surfaces of limbs predominantly yellow (vs. predominantly blue with dark-brown mottling), and advertisement call a single buzz or chirp containing either evenly spaced or discretely clumped pulses (vs. advertisement call a short buzz normally followed by 1–7 clicks); from L. daraiensis sp. nov. by its larger size (male SVL> 27.0 mm vs. 23.9 mm), having (vs. lacking) a distinct white bar below the eye, and distinct advertisement call (a single buzz or chirp containing either evenly spaced or discretely clumped pulses vs. 10–11 distinctly pulsed chattering notes); from L. gracilis sp. nov. by having a predominantly green dorsum with darker green and brown spots (vs. predominantly brown with green spots), having (vs. lacking) a distinct white bar beneath the eye, and advertisement call a single buzz or chirp containing either evenly spaced or discretely clumped pulses (vs. call containing 2–5 distinctly pulsed notes); from L. haematogaster sp. nov. by lacking (vs. having) large conical tubercles along outer edge of tarsi and arms, and hidden surfaces of limbs yellow (vs. red); from L. iris by having hidden surfaces of limbs predominantly yellow (vs. posterior of thighs blue, red, or yellow, frequently blotched with white or purple), violet spots in axilla and groin absent (vs. present) and advertisement call a single buzz or chirp containing either evenly spaced or discretely clumped pulses (vs. advertisement call a series of up to 10 notes of variable length, with long notes preceding or following short notes); from L. majikthise by its smaller size ( L. majikthise males 30–35 mm SVL), having posterior surfaces of thighs yellow (vs. uniform red), and lacking violet patches on posteroventral surfaces of abdomen (vs. present); from L. nigropunctata by having dermal folds along outer margins of tarsi distinctly crenulated (vs. dermal folds forming low dermal ridge), prominent white bar below eye present (vs. absent) and advertisement call a single buzz or chirp containing either evenly spaced or discretely clumped pulses (vs. advertisement call comprising an irregular succession of clicks and buzzes; Menzies 1972); from L. richardsi and L. singadanae in having a smaller (TYM/ EYE 0.39–0.50 vs. 0.65–0.81), pigmented (vs. substantially transparent) tympanum, and further from L. richardsi in lacking (vs. having) irregular black lines on dorsum and extensive black markings ventrolaterally, and from L. singadanae in lacking (vs. having) extensive area of orange on posteroventral surfaces in life; from L. umarensis in having posterior surfaces of thighs yellow (vs. brown), and dorsum with green and brown spots (vs. normally uniform green); and from L. verae in its smaller size ( L. verae males 33–35 mm SVL), lacking (vs. having) small brown spots aligned transversely on dorsum, and having yellow (vs. orange) on posteroventral surfaces in life.

Distribution and ecology. Litoria lisae sp. nov. is known from lower montane forest on Gobe Ridge and Iagifu Ridge (including Arakubi) in the Kikori River basin of southern Papua New Guinea ( Fig. 4 ), where they appear to be restricted to limestone karst habitats ( Fig. 14 ). Although several individuals were seen on foliage near a shallow forest pool, calling males were encountered only on low foliage in areas with no evidence of surface water suitable for egg deposition ( Fig. 14A ) and have been heard vocalising from hidden refuges deep within limestone sinkholes ( Fig. 14B ). Females have not been detected, and neither eggs nor larvae have been encountered. It is possible that this species breeds in small, subterranean waterbodies within the karst terrain, but this remains to be confirmed. Frog communities at the known localities for L. lisae sp. nov. are otherwise dominated by direct-developing microhylid species.

IUCN Red List status. Litoria lisae sp. nov. is known from two areas within the Kikori River basin where extensive forest cover remains. However, logging operations are occurring widely within this catchment so until the species’ distribution, habitat requirements and any potential threats are better documented we recommend that it be listed as Data Deficient by the IUCN.

Etymology. The name lisae is an honorific for the senior author’s wife, Lisa Capon, in gratitude for her ongoing support of his research activities.

Molecular divergences. Based on analyses of a 787 base pair alignment from the mitochondrial ND4 gene and flanking tRNA L. lisae sp. nov. is most closely related to the clade including L. majikthise and L. haematogaster sp. nov., however it is deeply genetically divergent from both of these taxa (dA between the taxa of 0.13 and 0.14, Table 2 ). The two sequenced samples of L. lisae sp. nov. from localities 70 kilometres apart also showed some genetic divergence (p-distance 0.024).

Figures

FIGURE 4. Map showing the distributions of Litoria species newly described species in this paper, and Litoria singadanae from the Huon Peninsula, Papua New Guniea. Blue square = Litoria daraiensis sp. nov., yellow triangle = Litoria gracilis sp. nov., red circle = Litoria haematogaster sp. nov., pale blue circles = Litoria lisae sp. nov., pink diamond = Litoria naispela sp. nov. and purple diamond = Litoria singadanae. Arrows indicate the type localities for Litoria gracilis sp. nov. and Litoria lisae sp. nov..

FIGURE 11. Litoria lisae sp. nov. in life, A) holotype (SAMA R71689), B–C), paratype SAMA R71690 in dorsolateral and ventral views. Photos by S. Richards.

FIGURE 12. Litoria lisae sp. nov. holotype (SAMA R71689), A) dorsal and B) lateral view of head (scale bars = 5 mm), C) palmar view of hand, D) plantar view of foot (scale bars = 1 mm).

FIGURE 13. Wave form (amplitude over time; top) and spectrogram (frequency over time; bottom) of two types of advertisement call produced by Litoria lisae sp. nov. (SAMA R71689) recorded at an air temperature of 20.5°C. Note distinctly clumped nature of pulses in chirp call (left) compared to buzz call (right).

FIGURE 14. Lower montane forest on limestone substrate at Iagifu Ridge, Papua New Guinea. Males of Litoria lisae sp. nov. called from low foliage in the forest along the trail illustrated A), and from deep within crevices and sinkholes in the karst, such as the large crevice indicated in B). Photos by S. Richards.