Abstract
The taxonomic status of the ranid frog Abavorana luctuosa (Peters, 1871) was investigated using a combination of molecular and morphological data. The analyses revealed that A. luctuosa sensu lato is composed of two species in Borneo. One of these species agrees with the description of Rana decorata Mocquard, 1890 which is resurrected in the combination Abavorana decorata comb. nov. (Mocquard, 1890). Abavorana decorata is recovered as the sister lineage to the remainder of Abavorana and differs by a 16.0–17.0 % uncorrected pairwise sequence divergence from its congeners A. nazgul and A. luctuosa, respectively. It is distinguishable morphologically from A. luctuosa and A. nazgul by its ventral pattern (bold, black and white reticulations on its venter along with bold banding on the underside of hind limbs vs. generally immaculate and spotted in the latter two species), and a prominent white streak beneath the eye and/or tympanum extending to the corner of the jaw. Abavorana decorata further differs from A. luctuosa by having a significantly wider head and snout, larger interorbital and tympanum diameters, longer femur in both sexes, and various combinations of other mensural characters. Both species are sympatric in Borneo and this discovery adds to a growing number of widespread Sundaic species shown to be species complexes with distinct forms in Borneo.
Key words: amphibia, biodiversity, conservation, endemic, herpetofauna, phylogeny, Sundaland, systematics
Diagnosis: Body robust, medium-sized; head moderate; snout short, rounded, canthus rostralis smoothly rounded; interorbital space broader than the upper eyelid; tympanum distinct, not quite two-thirds the size of the eye with no pale colouration on the margins of the tympanum; no vocal sacs in males; vomerine teeth in two small oblique patches on a level with the posterior edge of the choanae; length of 1st finger greater than 2nd finger; disc width to finger width ratios of finger 3 and toe 4 is 1–1.5; dorsolateral fold indistinct or absent; the humeral gland in males is prominent, raised and centrally positioned on the ventral surface of the upper arm; a weak or absent rictal ridge; outer metatarsal tubercle weak or absent; subarticular tubercles moderate; skin of dorsum smooth or finely shagreened; throat, abdomen, and flanks smooth; posterior section of venter and back of the thigh rugose; dorsum reddish-orange to chocolate-brown, encircled by a white or cream coloured dorsolateral line that encircles the snout, canthus rostralis, outer edge of the upper eyelids, and dorsum along the dorsolateral fold to the vent; lower flanks dark-brown or black below the dorsolateral line grading into a paler venter; dorsal colouration of the limbs same as the flanks with whitish or light-grey speckles or stripes. Abavorana luctuosa can be easily differentiated from its congeners on the basis of its ventral colour pattern which is usually immaculate or with only very faint, sparse, light speckling (Figs 3, 4, 9A–B). Adult males with SVL 35.05–44.27 mm, adult females with SVL 37.05–51.06 mm; adult males with SW 7.11–8.62 mm, adult females with SW 7.65–9.38 mm; adult males with IOD 3.25–5.14 mm, adult females with IOD 3.80–5.64 mm; adult males with TD 2.50–3.83 mm, adult females with TD 2.95–4.24 mm; adult males with FL 17.81–22.04 mm, adult females with FL 19.13–26.37 mm (Table 5).
Distribution: Its distribution spans southern Peninsular Thailand, Peninsular Malaysia, Borneo, and Sumatra (Manthey & Grossmann 1997; Oliver et al. 2015; Quah et al. 2017). Within Borneo it is confirmed from Sabah state: Imbak Canyon and Sipitang; Sarawak state: Bukit Kana, Samarakan and Tubau in Bintulu Division and Kubah National Park where it is sympatric with Abavorana decorata (Fig. 10). The species is expected to range across Borneo.
Abavorana decorata comb. nov. (Mocquard, 1890)
Decorated Mahogany Frog Figs 5, 6, 7A–D, 9C–D
Rana decorata: Mocquard 1890:145–146; Guibé 1950:41
Diagnosis: In addition to its phylogenetic placement (Fig. 1), Rana decorata is reassigned as a member of the genus Abavorana based on the combination of having a robust, medium-sized body; no vocal sacs in males; length of 1st finger greater than 2nd finger; disc width to finger width ratios of finger 3 and toe 4 is 1–1.5; dorsolateral fold indistinct or absent; the colour of the dorsolateral line being white or yellow; the humeral gland in males is prominent, raised and centrally positioned on the ventral surface of the upper arm; a weak or absent rictal ridge; outer metatarsal tubercle weak or absent; skin of dorsum smooth or finely shagreened; throat, abdomen and flanks smooth; posterior section of venter and back of the thigh rugose; no pale colouration on the margins of the tympanum; flanks dark-brown or black below the dorsal fold grading into a pale venter (Inger 1966; Oliver et al. 2015; Quah et al. 2017). Dorsum reddish-orange to rust-brown, encircled by a white or cream coloured dorsolateral line that encircles the snout, canthus rostralis, outer edge of the upper eyelids, and dorsum along the dorsolateral fold to the vent; lower flanks dark-brown or black below the dorsolateral line grading into a paler venter; dorsal colouration of the limbs light-grey or brown with speckling and prominent dark-brown or black bands. Abavorana decorata can be differentiated from its congeners on the basis of its ventral colour pattern which is reticulated in black and white especially on the lower flanks, underside of the limbs (especially hind-limbs) are boldly banded in black and white, and a prominent white streak under the eye and/or tympanum to the corner of the jaw (Figs 5, 6, 9C–D). Adult males with SVL 46.21–56.0 mm, adult females with SVL 29.66–58.42 mm; adult males with SW 9.91–10.71 mm, adult females with SW 6.25–11.68 mm; adult males with IOD 5.59–5.95 mm, adult females with IOD 3.91–6.78 mm; adult males with TD 4.54–4.60 mm, adult females with TD 2.27–5.63 mm; adult males with FL 25.58–26.10 mm, adult females with FL 17.19–31.34 mm (Table 5).
Distribution. Endemic to Borneo. The species is known from Sabah state, Malaysian Borneo: Mount Kinabalu, Kampung Kiau Taburi, Danum Valley, Tawau Hills Park, Maliau Basin, Tambunan and Penampang (CalPhotos ID: 0000 0000 0912 1159); Sarawak state, Malaysia Borneo: Kubah National Park (Fig. 7C) and Bario (Fig. 6A–B); and West Kalimantan, Indonesia: Melawi Regency (Fig. 7D). The species is expected to be wider ranging on the island.
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Figure 9. Colour pattern comparison among species of the genus Abavorana; Dorsum (A,C & E) and venter (B,D & F) in life of
A. luctuosa (USMHC 2576) (A & B) from Penang Hill, Penang Island, Malaysia,
A. decorata from Maliau Basin, Sabah, East Malaysia, Borneo (C & D)
and A. nazgul (USMHC 2233) (E & F) from Gunung Jerai, Kedah, West Malaysia.
(Photographs by Evan Quah [A, B, E & F] and Stefan T. Hertwig [C & D]). |
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| Figure 10. Distribution map of Abavorana decorata and A. luctuosa in Borneo; Known distribution of Abavorana decorata (red) and A. luctuosa (blue) in Borneo. Star = type locality. |
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Figure 8. Peninsular Malaysian, Thai and Sumatran Abavorana luctuosa, and A. nazgul;
A: A. luctuosa from Sungai Durian Forest Reserve, Kelantan, Peninsular Malaysia. B: A. luctuosa from Janda Baik, Pahang, Peninsular Malaysia. C: A. luctuosa from Semenyih, Selangor, Peninsular Malaysia. D: A. luctuosa from Fraser’s Hill, Pahang, Peninsular Malaysia. E: A. luctuosa from Hala-Bala Wildlife Sanctuary, Thailand. F: A. luctuosa from Sumatra, Indonesia.
G: A. nazgul (USMHC 2572) from Gunung Jerai, Kedah, Peninsular Malaysia. H. A. cf. nazgul from Thale Ban National Park, Satun Province, Thailand.
(Photographs by Zaharil Dzulkafly [A], Steven Wong [B], Kurt H.P. Guek [C], Evan Quah [D & G], Ian Dugdale [E], Hellen Kurniati [F] & Bunyarit Dechochai [H]). |
Abavorana nazgul Quah, Shahrul Anuar, Grismer, Wood, Siti Azizah & Muin 2017
Gunung Jerai Black Stream-Frog
Rana luctuosa Sukumaran, J. 2005: 38
Diagnosis: Abavorana nazgul can be differentiated from its congeners by the following combination of characters: adult males 41.51–44.1 mm SVL and single adult female 52.51 mm; adult males with SW 7.98–8.70 mm, single adult female SW 9.59 mm; adult males with IOD 3.94–4.48 mm, single adult female IOD 4.94 mm; adult males with TD 3.52–4.01 mm, single adult female TD 4.10 mm; adult males with FL 22.20–23.22 mm, single adult female FL 27.80 mm; nuptial pads absent in males; humeral glands in males small (2.4–2.98 mm) (Table 5); dorsolateral stripe continuous, orange to yellow in colour; dorsum between dorsolateral stripes black, with or without faint orange or yellow speckles; flanks black, colouration unstratified; distinct cream-colored spots on flanks, dorsal surfaces of limbs, and upper lip; venter grey-brown with prominent light spots on throat and belly, smaller spots on underside of thigh (Fig. 9E–F; Quah et al. 2017).
Distribution: Abavorana nazgul is thus far confirmed from the upper elevations of Gunung Jerai, Kedah, Peninsular Malaysia (Quah et al. 2017). Specimens resembling this species have been photographed at Thale Ban National Park, Satun Province in southern Thailand at approximately 500–600m in elevation around wild boar wallows but are only tentatively identified as A. cf. nazgul pending positive evidence (Fig. 8H).
