Litoria watjulumensis ( Copland, 1957 )

Donnellan, Stephen C., Catalano, Sarah R., Pederson, Stephen, Mitchell, Kieren J., Suhendran, Aidan, Price, Luke C., Doughty, Paul & Richards, Stephen J., 2021, Revision of the Litoria watjulumensis (Anura: Pelodryadidae) group from the Australian monsoonal tropics, including the resurrection of L. spaldingi, Zootaxa 4933 (2), pp. 211-240 : 220-225

Litoria watjulumensis ( Copland, 1957)

Wotjulum Frog

( Figs 5 , 6 , 7 )

Hyla latoplamata watjulumensis Copland, 1957

Lectotype. WAM R 11896, an adult female, collected at Wotjulum , Western Australia (16°11’ S, 123°37’ E) by A.M. Douglas.

Material examined. Specimens from WA and NT are listed in the Appendix I.

Lectotype measurements (mm): SVL = 46.6, HL = 19.0, HW = 16.1, TD = 3,5, ED = 5.1, EN = 5.1, IOD = 8.0, IND = 4.5, FLL = 11.3, Fin3L = 7.2, TL = 31.7, Toe4L = 22.3.

Diagnosis. Distinguished from other Australian Litoria (except L. spaldingi ) by a combination of: vomerine teeth present; distinct tympanum; strong head stripe, covering tympanum; grey to brown colouration in life, with dark variegations and infused with yellow which is prominent in males ( Fig. 5 ); black shin; inner thigh colouration comprises variously shaped yellow to orange or light brown spots on a darker brown to black background ( Fig. 6 ); fingers without webbing; fully webbed feet; and moderately expanded terminal discs on all digits ( Fig. 7 ), and a complex advertisement call that comprises sporadic chicken-like clucks, followed by a long series of rapid evenly spaced notes followed by more clucks. Morphologically shares the external features of L. spaldingi and has a similarly structured advertisement call, but is distinguished from that species by divergence in mitochondrial and nuclear DNA markers ( Figs 2 , 3 ). From a genetic perspective, apomorphic nucleotide states at nine and three sites in the mitochondrial ND4 and the nuclear PTPN12 genes respectively reliably diagnose L. watjulumensis from L. spaldingi ( Table 5 ).

A)

B)

Description including variation. Assessment of morphological variation is based on 35 females and 39 males ( Table 2 ). Mean SVL: females = 49 mm, males = 36 mm. Head slightly longer than broad (HL/HW 1.24) and approximately one-third of SVL (HL/SVL 0.39). Snout prominent, blunt when viewed from above and in profile. Nostrils more lateral than superior, closer to tip of snout than to eye. Distance between eye and naris equal to internarial span (EN/IND 1.03). Canthus rostralis well defined and straight. Eye relatively large, its diameter greater than eye to naris distance. Pupil horizontal when constricted. Tympanum distinct, circular, length slightly greater than half eye diameter (TD/ED 0.66). Vomerine teeth short straight plates bridging the gap between the choanae. Tongue approximately rectangular.

Fingers long, slender, unwebbed. Subarticular and palmar tubercles prominent. Terminal discs not wider than fingers. Dark brown nuptial pad on upper and inner surface of the proximal half of the first finger. Fingers in order of length 3>4>1>2. Hindlimb length moderate (TL/SVL 0.64). Toes in order of length 4>5=3>2>1. Webbing reaches base of second most distal phalanx on toe 4 and penultimate phalanx on other toes. Subarticular tubercles prominent. Small oval inner metatarsal tubercle prominent. Terminal toe discs not wider than toes.

Dorsum either smooth or with low and infrequent tubercules sometimes forming lines parallel to long axis of the body. Limbs with low tubercules, sometimes smooth. Abdomen, undersurface of thighs, and lateral aspect of body mildly granular. Pectoral fold absent in a majority of specimens and when present is indistinct. Vocal slit at base of mandible aligned along posterior-anterior axis, approximately one third length of mandible.

Colour in life. Dorsum pale to light brown, often heavily mottled with dark brown and in some individuals additional red mottling, imparting an overall impression of a more-or-less uniformly light or dark brown animal ( Fig. 5 ). Upper surfaces of limbs with same colour as dorsum, rarely with dark flecks. In calling males, yellow is suffused along the dorso-lateral edge of the dorsum from the eye to the groin and onto the lower dorsum. Head pale to light brown with dark brown stripe beginning at tip of snout becoming more prominent after the nostril but confined to upper edge of canthus rostralis, continuing past the eye to mid-body, with width same as eye and encompassing tympanum. In calling males, head often suffused with yellow. In some individuals, dark blotches from dorsal end of side stripe to groin. In all individuals lower lip has prominent light and dark brown patching. For some individuals the upper lip has the same patterning as the lower lip, otherwise upper lip is immaculate. Dorsal surface of the head often lighter than rest of the dorsum due to reduced frequency and extent of darker mottling.

Rear of thighs mostly dark brown, often same colour as head stripe with numerous yellow, circular to linearshaped spots and patches occupying between 20–70% of the rear of the thigh ( Fig. 6 ). Vent same colour as surrounding dorsal colours. Fore of thighs and groin with same colour and pattern as rear of thigh but separated from rear thigh pattern by intrusion of dorsal edge of thigh. Outer margin of foot with lighter upper surface distinctly bordered by dark brown of plantar surface.

Abdomen plain white, lower abdomen sometimes suffused with light brown flecking, otherwise immaculate. Throat sometimes with small indistinct dark brown mottling otherwise unpigmented. Upper iris red margined with a distinct white band that appears continuous with upper margin of facial stripe, lower iris same dark brown colourations as facial stripe.

Distribution and habitat. Occurs in the IBRA (Interim Biological Regionalisation of Australia) regions of Dampierland, Northern Kimberley, Central Kimberley, Victoria Bonaparte, Ord Victoria Plain, and Tanami ( Fig. 1 ). The most western locality is the Stewart River, Kimbolton (WAM R51854), the most eastern is in the Victoria River catchment in Gregory National Park (NTM R37297–8), and the most southern is Slatey Creek in the Sturt Creek catchment in the north-western Tanami (WAM R132982).

Breeding biology. Francis (2013) described the breeding biology from the east Kimberley region of Western Australia where it breeds in elevated rocky pools early in the wet season. Anstis (2013) presented a combined description of variation in embryos and larvae of L. watjulumensis and L. spaldingi , only noting where particular individual sampled localities departed in individual trait states from the remainder. However, Anstis did not note any difference between groups of the sites that we could allocate to L. spaldingi vs L. watjulumensis based on geography.

Advertisement call. Tyler & Doughty (2009) describe the call of L. watjulumensis as very complex, comprising sporadic chicken-like clucks, followed by a rapid series of evenly spaced notes (3–4 per second) which abruptly double in rate without a pause for up to 30 seconds followed by more clucks. The clucks are typically given in response to other male calls ( Tyler & Doughty 2009). Hoskin et al. (2015) present an audio file of the advertisement call of a male from Kununurra.

Our analysis is based on a sequence of 100 calls from one male (WAM R162508) of 165 s duration. Calls are complex and there is substantial variation in structural components within the sequence. However, calls can be grouped for convenience into three major types: 1) ‘clucks’ (53%), 2) ‘short calls’ (39%) and 3) ‘long calls’ (8%).

Clucks are sharp notes produced singly or in short bursts, with each note lasting 0.02– 0.04 s (mean = 0.03, SD = 0.005, n = 38). Clucks may be pulsatile, with the extent of amplitude modulation of pulses, including the proportion of pulses achieving 100% amplitude modulation, varying both within and between clucks; or they may comprise a single pulse.

Short calls last 0.35– 1.00 s (mean = 0.48, SD = 0.13, n = 30) and comprise two discrete components. The first is a series of 3–8 (mean = 3.73, SD = 1.16, n = 41) slowly repeated introductory cluck notes produced at intervals of about 0.04– 0.05 s, although this is variable. Twenty-two (53.7%) short calls have three introductory notes, and 15 (36.6%) have four introductory notes; just four short calls have between five and eight introductory notes. Introductory notes are pulsatile and frequently exhibit 100% amplitude modulation between 2–3 distinct pulses; the final pulse is normally significantly longer than preceding pulses. The second component of short calls is a rapidly repeated series of about 4–7 terminal notes produced at short intervals that are difficult to measure accurately. Terminal notes are finely pulsed and in total this second component of short calls lasts 0.13– 0.19 s (mean = 0.16, SD = 0.02, n = 28). Note repetition rate does not shift noticeably during the second component of short calls. Short calls sound like a series of clucks followed by a short, harsh buzz.

Long calls are a train of rapidly repeated notes that is at least eight times longer than short calls (8.6– 16.4 s; mean = 12.1, SD = 2.8, n = 8). Eight long calls contain 82–142 notes (mean = 109.4, SD = 20.7) produced at an overall repetition rate of 8.4–10.0 notes/s (mean = 9.1, SD = 0.6). However, although note rate does not change noticeably during the first half of the call, it nearly doubles from 6.7–7.1 notes/s (mean = 6.91, SD = 0.19) to 11.5–13.2 notes/s (mean = 12.57, SD = 0.54) at a sharp boundary (between two consecutive notes) between 48.2 and 71.0% of the way through the call (mean = 61.70%, SD = 9.08) ( Fig. 8A ). Amplitude is low at the start and increases rapidly for the first ~10-15% of the call then more gradually until it reaches maximum amplitude near the end of the call. Notes are very finely pulsed, and there may be a ‘supplementary’ terminal pulse that is separated from preceding pulses by about 0.004 s, although this is variable among calls. Notes within long calls are similar to cluck calls but are generally longer. The length of 20 notes measured from before, and 20 from after, the switch from ‘slow’ to ‘fast’ note rate in the first recorded long call of WAM R162508 are 0.04– 0.05 s (mean = 0.048, SD = 0.004, n = 20) and 0.04- 0.5 s (mean = 0.049, SD = 0.003, n = 20), versus note length of 0.02– 0.04 s in cluck calls.

Frequency is broadly distributed in the three call types ( Fig. 8A ) so they have a harsh quality. Dominant frequency of the call types overlaps broadly: 2760–3210 kHz (mean = 3023, SD = 154.4, n = 15) in clucks, 2731–3121 kHz (mean = 2981, SD = 97.92, n = 28) in short calls and 2857–3002 kHz (n = 8) in long calls.

Figure 8 illustrates a long call followed by a burst of clucks, then two short calls, five clucks, and 18 short calls followed by nine clucks.

Figures

FIGURE 1. Map showing the distribution of museum vouchers for the Litoria watjulumensis group (open small circles), vouchers that were analysed for morphometrics (solid black circles) and the collection locations for material that was analysed with molecular genetic techniques (orange [western] and blue [eastern] large triangles). Type locations for Hyla latopalmata watjulumensis and Hyla spaldingi are indicated by W and S respectively.

FIGURE 2. Phylogram of relationships among mitochondrial ND4 sequences of ground hylid group of Litoria. Numerical values at nodes represent ML bootstrap proportions (left) and Bayesian posterior probabilities (right).

FIGURE 3. Phylogram of relationships among the nuclear PTPN12 sequences of ground hylid group of Litoria. Numerical values at nodes represent ML bootstrap proportions (left) and Bayesian posterior probabilities (right).

FIGURE 5. Images of Litoria watjulumensis in life: A) male NTM R37217 from East Baines Crossing, Gregory NP, NT [D. Trembath], B) female NTM R37218 from East Baines Crossing, Gregory NP, NT [D. Trembath], C) male, WAM R162511 Grotto Creek, WA [P. Doughty]; D) WAM R173850 from Theda Station, WA [R. Ellis]; E) male, no voucher, from El Questro, WA [S. Mahony]; F) male, WAM R162598 Mount Leake, WA [P. Doughty].

FIGURE 6. Images of thighs in life showing color and pattern of Litoria spaldingi: A) WAM R23886 holotype; B) NTM R36092; C) NTM R36092 Darwin, NT; and Litoria watjulumensis: D) WAM R11896 lectotype; E) WAM R171464 Prince Regent River Nature Reserve; WA; F) WAM R164940 Bigge Island, WA.

FIGURE 7. Images of the preserved type of Hyla latopalmata watjulumensis, WAM R11896. A) dorsal, B) ventral, C) lateral head, D) palmar, and E) plantar views.

FIGURE 8. A) Waveform (top) and spectrogram (bottom) of part of a call sequence from Litoria watjulumensis (WAM R162508) recorded at The Grotto near Wyndham, WA, at a temperature of 28.3°C. Note the abrupt doubling of note repetition rate approximately 2/3 of the way through the long call. B) Waveform (top) and spectrogram (bottom) of part of a call sequence from a Litoria spaldingi (FrogID #6921) recorded 20 km southeast of Darwin, Northern Territory, illustrating 15 short calls and one long call (see text). Spectrograms generated using fast-Fourier Transform of 1024 points, 50% overlap, and Hamming Window.