Uperoleia trachyderma

Catullo, Renee A., Doughty, Paul & Keogh, J. Scott, 2014, A new frog species (Myobatrachidae: Uperoleia) from the Northern Deserts region of Australia, with a redescription of U. trachyderma, Zootaxa 3753 (3), pp. 251-262 : 255-256

Uperoleia trachyderma

Blacksoil Toadlet Fig. 2 & 3 c

Uperoleia trachyderma Tyler, Davies & Martin 1981 , Trans. R. Soc. S. Aust. 105, p. 49.

Uperoleia trachyderma Davies, McDonald & Corben 1986 , Proc. R. S. Vict. 98(4), p. 160.

Holotype. SAMA R20374 (male), collected on the Newcastle Creek floodplain at the George Redman Causeway, Northern Territory (17°14′S, 133°28′E) by M. Davies, A.A. Martin and M.J. Tyler on 16 December 1980.

Paratypes. KU 189561, NTM 9865, SAMA 20375–6. The series was collected with the holotype.

Type locality for Uperoleia trachyderma . The holotype for U. trachyderma ( SAMA R20374) was collected at Newcastle Creek, NT (17°14′S, 133°28′E) ( Fig. 2 ). This area corresponds with the distribution of the eastern Northern Deserts clade. In addition, the holotype was reported by Tyler et al. (1981b) to have a harsh ‘creak’ of four pulses as a call as well as orange tubercles on the dorsal surface, characteristics that have only been found in the U. trachyderma E nDNA clade individuals. Thus, based on available data, we have determined that the U. trachyderma holotype belongs to the U. trachyderma E nDNA clade.

Comment on previous descriptions. In the Davies et al. (1986) redescription of this species, a number of specimens were examined from the western side of the Northern Deserts. These localities do not fall into the range of U. trachyderma , and are likely to represent U. stridera sp. nov. These individuals and their locations were: SAMA R25952–61 from 113.9 km S Victoria Hwy/Delamere Hwy junction; SAMA R24017 from 415.1 km W Katherine on Victoria Hwy; and SAMA R24018–28 from 4.4 km W Keep River on Victoria Hwy.

Diagnosis. Distinguished from all other Uperoleia by a combination of small body size (males 18.1–22.1 mm SUL), flattened head (HD/SUL 0.15±0.01 [0.12–0.17]) broad snout (EN/IN 1.24±0.08 [1.14–1.36]), absence of maxillary teeth, finely tubercular skin, large red groin and femoral patches, large round parotoid glands reaching only to arms, well developed oval inguinal glands and large obvious coccygeal glands. Toes and fingers unwebbed, and highly reduced inner and outer metatarsal tubercles. Scattered light orange to red dorsal tubercles. A sharp click consisting of three to four pulses as an advertisement call.

Material examined. See Table 2 for specimens labeled as “ U. trachyderma ” under the nDNA clade column.

Description of series. Body size small, square and flattened in shape. Head is small, dorso-laterally compressed and shallow in depth. When viewed laterally, snout does not slope, tip is distinct and flattened; when viewed from above, the sides of the snout slope gradually to a sharp corner forming a flattened tip. Canthus rostralis prominent, slightly protruding and well defined; loreal region slopes to jaw and is only slightly convex. Moderate rounded medial projection (synthesis of mentomeckelian bones) that matches notch on upper jaw. Nostrils directed upward and slightly outward; nares have no visible rim. Anterior corner of eye covered by slight flap of skin. Posterior edge of brow does not project over side of head. Tympana covered by skin and parotoid glands. Tongue oval and elongate. Maxillary and vomerine teeth absent. EN larger than IN.

Arms and hands gracile. Arms are of moderate length and the fingers are moderately fringed and unwebbed. Finger length 3>4>2>1. Tubercles under fingers well developed; one on first and second, two on third and fourth. Well developed outer palmar tubercle on distal portion of wrist; well developed inner palmer tubercle on medial portion of wrist. Nuptial pad of males on outer portion of first finger (beginning 2/3 from attachment of finger), extending to base of wrist and encroaching on inner palmar tubercle.

Legs of moderate length and thin build. Toe length 4>3>5>2>1. Tubercles under toes well developed and conical; one on first and second, two on third and fifth, three on fourth. Toes moderately long, unwebbed, and strongly fringed. Small spade-shaped inner metatarsal tubercle along first toe. Outer metatarsal tubercle conical and highly reduced along fifth toe.

Dorsum covered in fine tubercles which extend down arms, legs, and across the ventral surface. Cloacal flap present, moderately fimbriated in males and status is unknown in females. Parotoid gland round, extremely well developed and obvious, starting from just behind eye and extending posteriorly to arms and to below the angle of the jaw. Inguinal glands well developed, oblong, situated on the side of the body, extending from approximately halfway between arm and leg to the groin coloration; posterior half of gland covered when leg is normally situated. Coccygeal glands large, round and obvious; situated on the torso above the legs. No glands evident between inguinal and parotoid glands. Mandibular gland moderately developed, disrupted, and situated alongside the parotoid gland at the corner of the jaw.

Coloration. Dorsal ground color frequently a rich medium brown, but a few individuals tended towards a grayish brown. Some individuals displayed solid dorsal coloration, while in others the dorsal pigment was mottled with darker spots of a similar color. All individuals displayed scattered dorsal tubercles that ranged from light orange to red. In most individuals the glands were slightly paler than the remaining dorsal surface. A slightly darker V, pointing posteriorly, was present between the eyes of most individuals. Groin and femoral coloration, usually extending down to top of the crus, was universally red. All males had darkly pigmented chins, with the dark pigment extending just posterior to the arms. The belly of all individuals is a cream color with scattered darker spots, which becomes blotchy as it nears the legs, then ceases abruptly. Ventral background pigment, except for a faint scattering of cream tubercles in some individuals, is not present on the thigh region any individuals examined.

Advertisement call. Figure 1 c and Table 1 summarize the main features of the call. This species produces a short sharp sound, audible as a slow click. All individuals of U. trachyderma gave calls consisting of three pulses ( Fig. 1 c), although some individuals also gave intermittently gave four-pulse calls. The four-pulse calls had a similar pulse rate to the three-pulse calls. Call rate of U. trachyderma was significantly lower than the call rate for U. stridera sp. nov.

Habitat. High population densities in protected claypan swamps, in chorus with Cyclorana maculosa , Litoria rubella , and L. caerulea . Individuals in low-density populations were found in boggy portions of pastures and ditches. This species appears to prefer fine soils such as blacksoil, which become extremely soft when wet. This may be associated with the extremely small size and highly reduced metatarsal tubercles, which would limit burrowing capabilities in other soil types.

Distribution. Found in the eastern portion of the Northern Deserts region: from approximately Cloncurry, Queensland, to east of Daly Waters, Northern Territory ( Fig. 2 d, Table 2). Like U. stridera sp. nov., ecological niche modeling suggests that the sandstone escarpments of the Top End biogeographic region represent the northern barrier to this species, and that the southern barrier corresponds with the 18th parallel, which is the approximate transition to extreme aridity and highly variable rainfall ( Catullo et al. 2013). These models also suggest that the Carpentarian Gap ( MacDonald 1969) represents a major barrier for the eastern side of the distribution.

Comparisons with other species. Uperoleia trachyderma can be distinguished from all species of Uperoleia except U. stridera sp. nov. by the combination of small size (SUL = 19.77 [1.34]), dorsal-lateral compression (HD/ SUL = 0.15 [0.01]) giving the frog a distinct flat aspect, extremely reduced metatarsal tubercles, and by the presence of fine dorsal tubercles. This species is distinguished from U. stridera sp. nov. by a lower pulse rate, a lower call rate, the presence of three or four pulses in the call versus two or three pulses ( Fig. 1 c, Table 1 ), and field location ( Fig. 2 d). This species is also distinguished by the presence of light orange to red dorsal tubercles, which are absent in U. stridera sp. nov.

Figures

FIGURE 1. Mitochondrial (a) and nuclear (b) phylogenies of U. stridera sp. nov. and U. trachyderma (modified from Catullo et al. 2013). Patterned bars indicate final species allocation based on genetics, morphology, and acoustics. Individuals with differing mitochondrial versus nuclear haplotypes are indicated by arrows. Oscillogram and spectrograms for the holotype of U. stridera sp. nov. (Up 0261, WAM R 164738, from near Fitzroy Crossing, WA) and U. trachyderma (Up 1091, NTM R 36190, from Bullwaddy Conservation Reserve, NT) are pictured in (c). Oscillograms display amplitude (y-axis) against time (x-axis), and spectrograms display frequency (y-axis) against time (x-axis). Time for each graph is one second.

FIGURE 2. Map of the Australian Monsoonal Tropics showing the distribution of (a) nDNA groups, (b) mtDNA clades, (c) acoustic variation, and (d) total known distribution of U. stridera sp. nov (green) and U. trachyderma (yellow) based on our data and previous taxonomic descriptions. Half coloured shapes in (b) indicate locations with multiple mtDNA clades present. Arrowheads in (d) indicate type localities. In (a), major bioregions are in bold, and biogeographical barriers are in italics. In (b), dashed lines indicate major roads and dots indicate locations. Modified from Catullo et al. 2013.

FIGURE 3. (a) Dorsal, dorsolateral, and ventral photos of the holotype of Uperoleia stridera sp. nov. (WAM R 164738); (b) Photos of U. trachyderma in life (NTM R 36190, R 36194, & R 36202); and (c) Photos of U. stridera sp. nov. (NTM R 36209, R 36212, & R 36213). Photos by M. Whitehead & R. Catullo.