Leptopelis rugosus (Ahl, 1924)

Goutte, Sandra, Reyes-Velasco, Jacobo, Kassie, Abeje & Boissinot, Stephane, 2022, Genetic and morphometric analyses of historical type specimens clarify the taxonomy of the Ethiopian Leptopelis gramineus species complex (Anura, Arthroleptidae), ZooKeys 1128, pp. 63-97 : 63

Leptopelis rugosus (Ahl, 1924)

Pseudocassina rugosa Ahl, 1924.

Pseudocassina ocellata Ahl, 1924.

Leptopelis montanus Tiutenko & Zinenko, 2021.

Type material.

Holotype. Adult female (ZMB-26915) collected during Oscar Neumann’s and Carlo von Erlanger’s expedition in 1900 in Meta, Kolla (approx. 9.17°N, 38.25°E, 2650 m a.s.l.).

Material examined.

In addition to the holotype, we examined one female collected at the end of July 1900 during O. Neumann’s and C. von Erlanger’s expedition in " Hochebene Didda " (ZMB-26913), which is one of the two syntypes of Leptopelis montanus Tiutenko & Zinenko, 2021 (= Pseudocassina ocellata ), synonymised here with L. rugosus . As this specimen was mentioned as "the holotype " by Largen (2001) and has a collection date and a more precise locality than the other syntype (ZMB-26914), which only states “Somaliand”, considered erroneous by ( Largen 1977), we formally designate ZMB-26913 as the lectotype of Pseudocassina ocellata here (see remarks below regarding the locality and taxonomic status). We also examined one female (16-130), collected on 12 July 2016 by J. Reyes-Velasco and S. Boissinot east of Mehal Meda (10.3316°N, 39.7812°E, 3265 m a.s.l.) , one male (16-103), collected on 12 July 2016 by J. Reyes-Velasco and S. Boissinot north of Debre Sina (9.9894°N, 39.7452°E, 3017 m a.s.l.) , three males (16-109, 16-116, 16-129), collected on 12 July 2016 by J. Reyes-Velasco and S. Boissinot east of Mehal Meda (10.16- 10.33°N, 39.76- 39.80°E, 3167-3265 m a.s.l.) , five males (16-150, 16-151, 16-152, 16-153, 16-154), collected on 13 July 2016 by J. Reyes-Velasco and S. Boissinot east of Debre Birhan (9.6979°N, 39.5628°E, 2833 m a.s.l.) , three males (16-164, 16-168, 16-172), collected on 14 July 2016 by J. Reyes-Velasco and S. Boissinot south of Fiche (9.73- 9.75°N, 38.74°E, 2657-2726 m a.s.l.) , five males (SB530, SB531, SB532, SB533, SB540), collected on 1 and 2 July 2018 by S. Goutte and Y. Bourgeois east of Debre Birhan (9.6979°N, 39.5628°E, 2339 m a.s.l.) , four males (SB541, SB542, SB544, SB545), collected on 2 July 2018 by S. Goutte and Y. Bourgeois between Debre Birhan and Ankober (9.6820°N, 39.7390°E, 3408 m a.s.l.) , two females (SB555, SB558) and one male (SB556), collected on 4 July 2018 by S. Goutte and Y. Bourgeois east of Mehal Meda (10.31- 10.33°N, 39.78- 39.80°E, 3337-3429 m a.s.l.) and three males (SB608, SB609, SB610), collected on 11 July 2018 by S. Goutte and Y. Bourgeois south of Fiche (9.7307°N, 38.7439°E, 2365 m a.s.l.) .

Diagnosis.

A large (male (n = 22) SVL 38.7 ± 2.7 mm, female (n = 2) SVL 52.4 ± 0.2 mm) species of the Leptopelis gramineus species complex (Figs 5 , 6 ). Robust, semi-fossorial form. It differs from other members of the Leptopelis gramineus species complex by the following combination of characters: (1) large tympanum (male TD/ED 0.57 ± 0.11, female TD/ED 0.54), (2) long snout (male SL/HL 0.25 ± 0.02, female SL/HL 0.27 ± 0.01), (3) well-developed metatarsal tubercle (male MTL/FL 0.17 ± 0.02, female MTL/FL 0.18 ± 0.02), (4) ventrum lacking any brown spots, (5) yellow colouration on the side of the ventrum and the inner thighs almost always present.

Comparison.

Larger body size, longer head and snout and greater snout-nostril distance and larger tympanum and metatarsal tubercle than L. gramineus , L. diffidens and L. sp. Kibre Mengist (Table 1 , Suppl. material 5: table S9). Longer hind-limbs than the Bale/Assela clade, but shorter than L. susanae (Table 1 , Suppl. material 5: table S9). Finger and toe discs less developed and head narrower and shorter than L. susanae (Table 1 , Suppl. material 5: table S9). Leptopelis rugosus is distinguished from the Bale/Assela clade by the lack of dark pigmentation on the ventrum, throat and ventral side of the limbs (Figs 6 , 7 ).

Description of the holotype.

Relatively large adult female (SVL 44.7 mm) in good condition of preservation (Fig. 5 ). Body robust and round. Head a third of body size in length, wider than long (HW/HL 1.21). Canthus rostralis obtuse and snout rounded and wide (IND/IOD 0.96). Nostril half-way between the tip of the snout and the eye (NS/SL 0.53). Tympanum partially hidden by flank skin rugosities and barely visible. Hind-limbs relatively long (TL/SVL 0.38 and THL/SVL 0.43). Finger and toe discs barely expanded, but distinct, ovoid. Finger formula: I <II <IV <III. Hand free of webbing. Foot longer than tibia (FL/TL 1.3). Inner metatarsal tubercle well-developed, oval in shape, 0.20 × foot length. Outer metatarsal tubercle absent. Toe formula: I <II <V <III <IV. Toe webbing formula (toe internal/external sides, number of phalanges webbed): Ie(1), IIi/e(1-1), IIIi/e(1-2), IVi/e(2-2), Vi(2). Skin of the dorsum, flanks and ventrum highly rugose.

Colouration of the holotype in preservative.

Dorsal ground colour and canthal region dark olive brown with no visible pattern, except for a large light brown blotch covering about a third of the dorsum (Fig. 5 ). This discolouration probably appeared during the specimen preservation and after its original description, where Ahl described the dorsum as "solid dark olive-brown". The thin light yellowish line noted by Ahl (1924) to extend to the upper arm is mostly faded away behind the tympanic region. Upper lip and flanks light yellowish-brown. Throat, ventrum, ventral side of the thighs and tibias light yellowish-brown. Front and hind-limbs olive brown without any marking.

Variations.

Leptopelis rugosus presents less colour polymorphism than the smaller members of the L. gramineus species complex. Dorsum is green to dark green and can be completely uniform or have a few to many irregular brown blotches (Fig. 6 ). In some individuals, these blotches form an irregular dorsal stripe extending from the top of the head to the lower back. A dark brown to black bar covers the canthal region and extends behind the eye, over the tympanum and sometimes behind the arm junction. This canthal stripe is overlined by a thin, more or less visible yellowish line. Flanks are the same colour as the dorsal ground colour and, in all individuals examined, except for the female SB558, have more or less well-defined brown ocelli. Limbs are the same colouration as the dorsum and rarely have irregular brown markings. Upper lip may be cream or a lighter shade of green than the dorsum without any markings. Iris sand colour to brown. Tympanum may be uniformly green or partially covered by a brown blotch joining the brown bar behind the eye. Throat and chest uniformly white to pale yellow. Ventrum generally white or cream with light to deep yellow zones on the sides extending to the ventral side of the thighs. In some individuals, the ventrum may be completely yellow. In gravid females, yellow eggs are visible through the thick ventral skin. In most individuals, the palms of the hands, ventral and inner sides of the limbs show very little to no dark pigmentation. Some individuals have a few irregular brown or black blotches on the inner tibia, forearm, hand and foot. Dorsal skin may be smooth, slightly or very rugose.

Habitat, distribution and natural history.

Leptopelis rugosus is found in grassy meadows of the Ethiopian Highlands north of the GRV at mid- to high elevations (2,339-3,337 m a.s.l.). This species occurs notably near Debre Birhan, Debre Sina, Fiche, Addis Ababa, Holeta and Ambo (Fig. 1 , Suppl. material 5: table S1). The northernmost population was found near Mehal Meda (10.3171°N, 39.8024°E), while the southernmost individuals were found between Ambo and Wonchi (8.9007°N, 37.8928°E). One of the two types in Ahl’s original description of Pseudocassina ocellata was collected on the Arussi Plateau, which, if the locality is correct, is the only known specimen east of the GRV (see remark on the type locality below).

Males are heard calling at night and sometimes during the day for extended periods of time. Advertisement calls are emitted from the ground, either on the grass or from a cavity in the ground or under a rock, generally near a stream or a flooded area. Several males were found calling from the banks of a completely dried-out stream, although it is unknown to us whether the reproduction period extends to the dry season or whether males keep calling only during shorter dry periods.

Advertisement call.

The call of Leptopelis rugosus is a short rattle composed of a single note of 65 ± 21 ms in duration, containing 4 ± 1 pulses (Fig. 4B ). In most individuals, the two first pulses are emitted at very short intervals, while the subsequent pulses are more spaced (average inter-pulse interval 20 ± 5 ms). Other individuals produce notes with regularly-spaced pulses. Amplitude is highest at the beginning of the note and decreases gradually. Within a call bout, calls are spaced by 13 ± 7 seconds, often with an acceleration of the call rate from a call every 10 seconds to one call per second. Call dominant frequency is 1,769 ± 60 Hz, with a bandwidth of 742 ± 82 Hz.

The call of Leptopelis rugosus is distinguishable from the calls of L. gramineus , L. diffidens and the Kibre Mengist and Bale/Assela clades by its lower number of pulses per note and narrower frequency band width. It is further distinguished from the call of L. gramineus , L. diffidens and L. sp. Kibre Mengist by its shorter note duration and from L. sp. Kibre Mengist by its lower peak frequency and higher pulse rate. Finally, it is distinguished from the call of L. susanae by its longer duration and lower pulse rate (Table 2 ).

Remarks.

Diagnostic characters used in the original description.

Ahl described Pseudocassina rugosa , based on a single female and provided three main diagnostic characters when compared with Pseudocassina ocellata , which he described in the same article, based on one female and one male: (1) the texture of the skin (rugose for P. rugosa and smooth for P. ocellata ), (2) the length of the tibia ( P. rugosa TL/SVL 1/3.5 and P. ocellata TL/SVL 1/3), (3) the visibility of the tympanum (hidden for P. rugosa and visible for P. ocellata ). Ahl also named P. ocellata after the presence of ocelli on the flanks of the individuals he examined, which reflects on its specificity, even though he did not use this trait as a diagnostic character.

We found individuals of L. rugosus and the Bale/Assela clade with either a completely smooth, slightly rugose or coarsely rugose dorsum. The rugosity of the skin thus seems to be variable amongst individuals and, perhaps, age or season. Additionally, we have noticed that the rugosity of the skin may disappear after euthanasia and/or fixation of the specimen. Finally, even though almost all individuals of L. diffidens , L. gramineus and the L. sp. Kibre Mengist examined had smooth skin, we found two females L. diffidens and one female L. sp. Kibre Mengist with slightly rugose skin. The visibility of the tympanum seems to be variable across the individuals as well, perhaps linked to the size of the individual and the rugosity of the skin. While some female L. rugosus have a partially hidden tympanum, all males examined had a visible tympanum. The difference in tibia length between the specimens described by Ahl reflects individual variations as shown in our dataset. Finally, ocelli on the flanks and/or dorsum are present in certain individuals of L. rugosus and the Bale/Assela clade and is not a diagnostic character.

Figures

Figure 1. Distribution ranges of six species of the Leptopelis gramineus species complex. Small, more arboreal forms are represented by green (L. diffidens), yellow (L. gramineus) and purple (L. xeniae sp. nov.) triangles. Larger, semi-fossorial forms are represented by red (L. rugosus) and white (L. shebellensis sp. nov.) circles. The large arboreal Leptopelis susanae is represented by a light blue triangle. Stars indicate type localities given in the original descriptions of L. gramineus (yellow; dashed line between Badditu and Dime), Pseudocassina rugosa (red) and Pseudocassina ocellata (grey), both synonymised here with L. rugosus (see the discussion in the main text).

Figure 4. Advertisement calls of six Leptopelis species inhabiting the Ethiopian Highlands A L. shebellensis sp. nov. (SB 61) B L. rugosus (SB 609) C L. gramineus (SB 212) D L. xeniae sp. nov. (SB 169) E L. diffidens (SB 134) F L. susanae (SB 223).

Figure 5. Dorsal and ventral views of the female holotype (ZMB- 26915) of Leptopelis rugosus.

Figure 6. Leptopelis rugosus A live male (SB 610; left) and female (SB 558; right) B dorsal and ventral views of male (SB 610) after euthanasia and before fixation C dorsal and ventral views of female (SB 558) after euthanasia and before fixation.

Figure 7. Leptopelis shebellensis sp. nov. A male holotype (SB 482; left) and live female paratype (SB 41; right) B male holotype (SB 482; left) and dorsal and ventral views of female paratype (SB 39; right) after fixation.