Litoria corbeni Wells and Wellington, 1985

Price, Luke C., Hoskin, Conrad J., Mahony, Michael J. & Donnellan, Stephen C., 2025, Systematic evaluation of molecular genetic, morphological and acoustic variation reveals three species in the Litoria revelata complex (Anura: Pelodryadidae), Zootaxa 5584 (3), pp. 301-338 : 320-323

Litoria corbeni Wells and Wellington, 1985

Atherton Tablelands Whirring Tree Frog

Fig. 10

Holotype: QM J30116 , by original designation, adult male. Type locality: Millaa Millaa Lookout , Atherton, Tableland, north-eastern Queensland, Australia, -17.62º, 145.5678º. Collected by G. J. Ingram on 1 November 1971. Amey & Couper (2022) illustrated dorsal, ventral and lateral views of the holotype.

Diagnosis. Litoria corbeni can be diagnosed from L. littlejohni and L. watsoni by its smaller size (23–33 mm vs 43–61 mm and 42–64 mm, respectively, sexes combined). Diagnosed from L. ewingii , L. paraewingi and L. verreauxii by expanded terminal discs on fingers and toes (vs terminal discs similar width, or only slightly wider than, terminal phalanges). Diagnosed from L. jervisiensis by termination of lateral head stripe near forearm (vs terminating along flank), dark patches in groin (vs absent), and smaller size (23–33 mm vs 37–44 mm, sexes combined). Litoria corbeni can be diagnosed further from the following species by its greater mean number of notes in the advertisement call (27.5, range 18–33 vs 2.3, range 1–4 in L. jervisiensis ; 8.8, range 5–16 in L. littlejohni ; 4, range 3–8 in L. paraewingi ; 9, range 8–11 in L. sibilus ; and 6.5, range 3–14 in L. watsoni ).

Litoria corbeni can be diagnosed from L. revelata by a higher pulse repetition rate (130.2 pps ± 4.5, range 127.3–136.7 vs 105.3 ± 10.10, range 86.9–127.3) ( Table 6 ). It can be diagnosed from L. eungellensis sp. nov. by the absence of well-demarked, black spots or blotches along the margins of the lower hindlegs, and by a higher mean pulse repetition rate (130.2 pps ± 4.5, range 127.3–136.7 vs 78.1 ± 10.7, range 66.9–86.2) ( Table 6 ). Litoria corbeni can also be diagnosed from L. revelata and L. eungellensis sp. nov. by apomorphic states at 30 and 34 nucleotide sites respectively in the ND4 gene alignment ( Table 3 ).

Measurements of holotype (mm). SVL 30.12, HL 9.72, HW 9.57, TL 17.55, TD 1.41, ED 3.03.

Description. A summary of variation in 14 mensural characters and five ratios is presented in Table 4 . Mean SVL: females = 32.1 ± 0.94, 31–33.6 mm; males = 27.8 ± 2.07, 23.7–32.4 mm.

Snout; rounded when viewed from above, blunt or rounded in profile. Nostrils more lateral than superior; closer to tip of snout than to eye. Canthus rostralis well-defined, and straight. Head length shorter than, to a bit longer than, head width (HL/HW 0.81–1.07), approximately one-third of SVL (HL/SVL 0.29, 0.23–0.34). Pupil horizontal when constricted ( Fig. 10 ). Eye relatively large (ED/HL 0.4, 0.34–0.44). Tympanum distinct; circular; diameter variable (TD/ED 0.5, 0.38–0.7). Vomerine teeth in short straight rows from anterior edge of choanae to midline of palate (assessed in SAMA R72459).

Fingers long, narrow; webbing absent. Subarticular and palmar tubercles prominent. Terminal discs prominent. Fingers in order of length: 3>4>2>1. Dark brown nuptial pad wraps around upper surface of base of finger I (SAMA R34328–9, R63777, RI72458–9).

Hindlimb length moderate, but variable (TL/SVL 0.5, 0.45–0.6). Toes in order of length: 4>5=3>2>1. Webbing on toes I, II, III, V reaches base of toe disc, and on toe IV to base of the penultimate phalanx. Subarticular tubercles prominent. Rectangular inner metatarsal tubercle approximately one-quarter length of first toe. Terminal discs prominent, but smaller than finger discs.

Dorsum finely granular. Upper surface of limbs smooth or finely granular. Flanks with dense coverage of low tubercles. Chin, abdomen, undersurface of limbs, and lateral aspect of body coarsely granular or granularity confined to lateral margins of abdomen.

Colour in life. Dorsum tan, grey-brown, cream-brown or reddish-brown, continuing onto flanks; in most individuals, middle of dorsum has distinct darker shading that starts with well demarked margin between eyes. Some individuals with small to minute dark flecks over dorsal surfaces and flanks. A dark or light brown stripe, with a lower margin that is often poorly defined, extends from nostril along canthus rostralis through eye to just past forearm, and sometimes incorporates tympanum. Ventral surfaces white to cream, with small dark spots either peripherally or over entire ventral surface ( Fig. 10C ). Upper iris bright copper-gold, lower iris brown copper-gold Vocal sac pigmented light yellowish cream ( Fig. 10C ).

Axilla in two of six vouchers examined (33%) with dark marks, remainder with axillae same colour as flanks or covered by diffuse extension of eye stripe. Groin with dark patch ( Fig. 10 ), and occasionally with smaller spots anterior to groin. Posterior of thighs either uniform orange ( Fig. 10 ) or with black spot at proximal margin ( Fig. 10 ). Underside of the hindlimbs lack dark marks ( Table 5 ).

Distribution. Known from elevations between about 700 and 1220 m a.s.l. on the western and southern Atherton Tablelands ( Fig. 1 ). Records form an ‘arc’ from the Mt Baldy area (near Atherton) on the western Atherton Tableland, to Ravenshoe and Millaa Millaa in the south, to the Topaz area in the south-east ( Fig. 1 ). Most sites on the western and southern Atherton Tableland are above 1000 m a.s.l. but some sites in the Millaa Millaa-Topaz area are lower (down to approximately 700 m a.s.l.).

Ecology and reproductive biology. Known to breed in both disturbed and natural situations where still or slow-moving water is within, or adjacent to, forest. Breeding sites are ponds (including farms dams; e.g., Fig. 11A ) and other stationary water bodies (e.g., Mt Hypipamee crater), and slow-flowing pools in streams (e.g., Fig. 11B ). Breeding occurs in rainforest and wet sclerophyll forest, and in habitats comprising mosaics of grazing land and rainforest, or wet sclerophyll forest. Most known breeding sites are in agricultural land where the frogs reproduce in farm dams or slow pools along disturbed creeklines, but all breeding sites have some forest in close proximity. Prior to extensive clearing of the southern Atherton Tablelands, breeding sites would have been natural ponds and pools along slow flowing streams through rainforest and wet sclerophyll forest.

Males call from riparian vegetation including reeds, sedges, tall grass, and adjacent bushes and trees. Calling has been heard through most of the year except for May and June (FrogID, CJH observations). Males are bright yellow when calling in the breeding season, whereas the few females encountered in the wild in the breeding season have been a more tan-brownish colour (CJH observations). Other aspects of reproductive biology are not known.

Conservation status. Litoria corbeni has a small distribution in an upland area, so warrants conservation assessment against IUCN Red List criteria (2012). The EOO (measured as a minimum convex polygon around all known sites) is about 795 km 2. The actual area occupied within this area (the AOO) would be much smaller, estimated as 76 km 2. All known sites are above 700 m a.s.l. and most are above 1000 m a.s.l., in an area where there is limited suitable habitat over 1100 m a.s.l. and very little over 1200 m a.s.l.. The highest known record is about 1220 m a.s.l. Additionally, even at higher elevations (e.g.,> 1000 m a.s.l.), L. corbeni is patchy in occurrence, and the reason for the patchiness is not known. Whether the known sites represent one ‘location’ (a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals; IUCN 2012) or many can only be assessed based on the perceived threat. Fire may be a threat at wet sclerophyll sites on the west of the distribution, but most sites are associated with rainforest and grazing land in cool, wet areas that are unlikely to burn. Most known sites are on private land, where there is limited protection for regrowth rainforest; hence habitat loss and fragmentation through clearing is also a threat. However, the primary perceived threat is climate change, both gradual warming and the extremes of heatwaves and droughts.

Considering climate change as the primary threat, all sites are taken to represent one ‘location’. It is hard to assess this species against Criteria A, C, D and E due to limited data, but it can be assessed against Criterion B. Under Criterion B, with an EOO of 795 km 2 and AOO of 76 km 2, Litoria corbeni fulfils an Endangered B1/B2 (a, b) listing based on: B1 EOO <5,000 km 2 (but not <100 km 2 for Critically Endangered), B2 AOO threshold <500 km 2 (but not <10 km 2 for Critically Endangered), (a) number of locations <5; and (b) decline inferred or projected in (iii) area, extent and/or quality of habitat, (iv) number of subpopulations, and (v) number of mature individuals due to the ongoing effects of climate change.

Conservation of this species should include surveys to find additional breeding sites, monitoring of known breeding sites to assess continued occupancy, and revegetation along gullies throughout its known distribution. The southern Atherton Tablelands, where most populations of L. corbeni occur, was once forested but has been extensively cleared. Furthermore, the species occurs in relatively flat areas where it breeds in ponds and slow-moving creeks, which are areas preferred for farming. Most known breeding sites are now in or adjacent to remnant or regrowth rainforest in a matrix of forest patches and cleared gazing land. Although farm dams and gully lines offer breeding habitat, close proximity to forest is vital, so revegetation along gully lines will help to increase the area of rainforest habitat, increase the number of suitable breeding sites, and increase connectivity between them.

Figures

FIGURE 1. Map of eastern Australia showing collection locations and specimen records for the Litoria revelata complex, in the states of Queensland (Qld) and New South Wales (NSW). Genetically analysed specimens: blue dots—L. corbeni, red dots—L. eungellensis sp. nov., grey dots—L. revelata. Small black dots are specimen records from the Atlas of LivingAustralia. See Appendix 1 for location codes. Graded blue background represents the elevational gradient, with darker blue being higher elevations.

FIGURE 10. Litoria corbeni in life: A–C) no vouchers, upper Walsh River, Mount Baldy, photos Conrad Hoskin; D–F) no vouchers, Millaa Millaa area, photos Mark Sanders; G–H) no vouchers, southern Atherton Tableland, photos Luke Price.

FIGURE 11. Litoria corbeni habitat:A) Millaa Millaa area, photo Conrad Hoskin; B) upper Walsh River, Mt Baldy, Queensland, photo Conrad Hoskin.