Ptychadena beka, Goutte & Reyes-Velasco * & Freilich & Kassie & Boissinot, 2021

Goutte, Sandra, Reyes-Velasco *, Jacobo, Freilich, Xenia, Kassie, Abeje & Boissinot, Stephane, 2021, Taxonomic revision of grass frogs (Ptychadenidae, Ptychadena) endemic to the Ethiopian highlands, ZooKeys 1016, pp. 77-141 : 77

Ptychadena beka sp. nov.

Type material.

Holotype. Adult male (SB291) collected by S. Goutte and J. Reyes-Velasco on 5 June 2018 southwest of Nekemte (8.9950°N, 36.4955°E, 2213 m a.s.l.). Paratypes. one male (15-5) collected by X. Freilich, J. Reyes-Velasco and S. Boissinot on 3 August 2015 west of Holeta Genet (9.0508°N, 38.4312°E, 2433 m a.s.l.), one male (15-283) collected by X. Freilich, J. Reyes-Velasco and S. Boissinot on 14 August 2015 southwest of Nekemte (8.9742°N, 36.4906°E, 2243 m a.s.l.), one female (16-1) collected by J. Reyes-Velasco and S. Boissinot on 4 July 2016 west of Holeta Genet (9.05078°N, 38.4312°E, 2386 m a.s.l.), one female (SB268) collected by S. Goutte and J. Reyes-Velasco on 3 June 2018 northwest of Bonga (7.5085°N, 36.0637°E, 2038 m a.s.l.), 3 females (SB270, SB272 and SB276) collected by S. Goutte and J. Reyes-Velasco on 3 June 2018 south of Ambo (8.9671-8.9922°N, 37.7951-37.8471°E, 1945-2170 m a.s.l.), one female (SB282) collected by S. Goutte and J. Reyes-Velasco on 4 June 2018 southwest of Nekemte (8.9950°N, 36.4955°E, 2213 m a.s.l.), one female (SB287) and one male (SB292) collected by S. Goutte and J. Reyes-Velasco on 5 June 2018 southwest of Nekemte (8.9950°N, 36.4955°E, 2213 m a.s.l.), one male (SB387) collected by S. Goutte and J. Reyes-Velasco on 11 June 2018 south of Gech’a (7.5544°N, 35.4148°E, 1936 m a.s.l.), one male (SB471) collected by S. Goutte and Y. Bourgeois on 21 June 2018 east of Iteya (8.1275°N, 39.2732°E, 2138 m a.s.l.), one female (SB566) collected by S. Goutte and Y. Bourgeois north of Gohatsion (10.01967°N, 38.2494°E, 2448 m a.s.l.), one male (SB576) collected by S. Goutte and Y. Bourgeois on 7 July 2018 north of Gebre Guracha (9.8664°N, 38.3758°E, 2596 m a.s.l.), two males (SB614, SB617) collected by S. Goutte and Y. Bourgeois on 14 July 2018 east of Holeta Genet (9.0682°N, 38.5214°E, 2397 m a.s.l.). All specimens are deposited at ZNHM.

Diagnosis.

A medium-sized species (male (9) SVL 37.9 ± 2.6 mm, female (8) SVL 43.2 ± 2.9 mm) of the Ptychadena neumanni species group (Fig. 18 ), distinguished by the following combination of characters: (1) relatively short hind limbs (male TL/SVL 0.51 ± 0.03, female TL/SVL 0.57 ± 0.03), (2) tympanum with a light vertical bar, (3) medium or wide vertebral stripe always present, (4) vocal sacs of most males are bicolored, from light to dark grey posteriorly and from yellow to cream anteriorly, rarely, they are light grey, (5) forearms of adult males not thickened.

Comparison.

Ptychadena beka sp. nov. is smaller than P. cooperi and P. goweri and larger than P. nana and P. robeensis sp. nov. Hand, feet, tibias, thighs and snout are of similar dimensions than P. amharensis and shorter than those of P. delphina sp. nov. and P. goweri . Ptychadena beka sp. nov. can be distinguished from P. amharensis by a wider inter-orbital distance. It can be distinguished from P. erlangeri by a larger tympanum, the light stripe or blotch on the tympanum and the bicolored vocal sacs in adult males. Ptychadena beka sp. nov. differs from P. levenorum by longer thighs, larger tympanum and longer snout. The head is wider and the tibias are longer than in P. doro sp. nov.

Description of the holotype.

A medium-sized (SVL 36.3 mm) adult male (Fig. 18 ). Head slightly wider than long. Snout projecting beyond the lower jaw. Interorbital distance 0.62 × the eye diameter. Internarial distance 1.12 × interorbital distance. Tympanum 0.67 × eye diameter. Finger tips not expanded but rounded, with very small subarticular tubercles. Finger formula: I<II<IV<III. Hand free of webbing, palmar tubercle absent. Nuptial pads light grey. Hindlimbs moderately elongated, with tibia length 0.51 × snout-vent length. Foot as long as thigh and shorter than tibia (FL/TL0.97). Toe tips rounded. Subarticular tubercles extremely small. Inner metatarsal tubercle present, external absent. Toe formula: I<II<V<III<IV. Foot webbing formula: Ie(1), IIi/e(1-1), IIIi/e(1-2), IVi/e(2-2), Vi(2). Two light brown, continuous lateral ridges, two continuous and four interrupted dorsal ridges. No vertebral nor sacral ridges. No warts on the body. Small and round light brown warts on tibias and thighs.

Coloration of the holotype in life.

Dorsal ground color brown with a few small, elongated dark brown blotches symmetrically distributed on the dorsolateral ridges. Wide light brown vertebral stripe, doubled with a thin, clearer line from the tip of the snout to the vent. Dark brown canthal stripe from the tip of the snout to the back of the jaw. Faint light vertical stripe on the otherwise brown tympanum. Upper and lower lip cream with irregular brown markings.

Iris bicolored, with upper third light silver-grey, and the lower two thirds dark brown. Small irregular dark olive brown blotches on greyish flanks. Throat and chest cream, ventrum, ventral sides of the thighs and of the tibias light yellow. Two small symmetrical dark brown blotches on the antero-ventral side of the shoulders. Thin, light longitudinal stripe on the tibias. Few white round warts on the tibias. Hind limbs brown with dark olive bars over the thighs, tibias, and feet. A few very small round white dots around the groin. Back of the thighs dark brown irregularly molted with yellow. Vocal sacs dark grey anteriorly, yellow posteriorly.

Coloration of the holotype in preservative.

Dorsal ground color grey with a few oval dark brown blotches symmetrically distributed on the dorsolateral ridges. Wide light brown vertebral stripe, doubled with a lighter thin line from the tip of the snout to the vent. Dark brown canthal stripe from the tip of the snout to the back of the jaw. Faint vertical stripe on the otherwise brown tympanum. Upper lip and lower lip cream heavily blotched with grey. Flanks brown with a few black blotches underlined with a cream bar. Throat, ventrum, ventral side of the thighs and tibias cream, with the chest and throat dusted with grey. Two symmetrical dark brown blotches on the ventral side of the shoulders. Faint, thin longitudinal stripe on the tibias. Faint brown bars on the thigh and tibia. A few small round white spots forming a line on the posterior side of tibia and foot. Back of thighs molted light and dark brown. Vocal sacs dark grey anteriorly, cream posteriorly. Nuptial pads light grey.

Variations.

In life, background color varies from yellowish brown to greyish brown. Dorsal ridges vary in number and definition. In all examined specimens, median ridges were continuous from the back of the head to the groin. Postpalpebral fold usually interrupted in the middle of the back, sometimes continuing on the lower back by a ridge or multiple aligned warts. Short latero-dorsal fold almost always present, sometimes fractioned. Lateral ridges, briefly interrupted in a few specimens, most often continuous, from orange-brown to cream. All specimens examined had small dark brown or black blotches distributed symmetrically on the dorsal ridges, in very few specimens, those blotches were very small or barely visible. All examined individuals have a wide, generally around a lighter thin stripe. The light blotch on the tympanum is generally small and more conspicuous in some specimens than in others. The thin cream longitudinal stripe on the tibia may be more or less conspicuous and extended to half of the thigh in some individuals. Tibias, thighs and feet posteriorly barred with more or less defined brown or light brown markings. Yellow and brown marbling on the posterior side of the thighs more or less contrasted and almost absent in some individuals. Ventrum and throat uniformly white to light yellow. Vocal sacs grey, bicolored cream to yellow and light grey to grey. Small warts over the back and flanks in ca. 10% of adult males examined.

Etymology.

The specific name corresponds to the translation of the word “enough” or “that’s it" in Amharic (በቃ), in reference to the controversial taxonomic history of the group that we hope has come to an end. It is an invariable noun used in apposition.

Habitat, distribution, and natural history.

Ptychadena beka sp. nov. has a wide distribution range extending both sides of the Great Rift Valley, although most records were made west of the GRV (6.14-10.01°N, 35.41-39.27°E). It is restricted to moderate altitudes, from 1695 m to 2596 m a.s.l. (based on 106 barcoded individuals). In the north, its range is limited by the Blue Nile valley and the northernmost specimens have been found just north of Gohatsion. The westernmost population has been found in Gech’a. Two populations have been found southeast of the GRV, near Iteya and south of Irba Muda. GPS coordinates for all examined specimens are given in Suppl. material 3: Table S1. Ptychadena beka sp. nov. is found in syntopy with P. erlangeri at the higher end of its altitudinal range, notably near Fitche, Holeta, between Ambo and Wonchi, and possibly near Assela. Within the genus, P. beka sp. nov. is also sympatric with P. neumanni , P. delphina , and P. doro in the west.

Males are found calling at in shallow roadside puddles or agricultural fields. Males can be found vocalizing very close from one another, sometimes in important numbers. Calling activity depends on rainfall and is highest during rainy months. Calling usually starts after 22:00, and sometimes as late as 02:00 in dry weather, and ceases before dawn. Numerous, small bicolored eggs are laid in the same water body.

Advertisement call.

The call of Ptychadena beka sp. nov. (5 males, 128 calls) is composed of a single pulsed note of 447 ± 112 ms in duration, containing 31 ± 10.6 pulses. Within calls, pulses are grouped by 3-5 pulses, with the first and the last pulses of each pulse group notably lower in amplitude than the other pulses. Low-amplitude single pulses are sometimes present between pulse groups. Amplitude increases gradually during the call, peaking at 266 ± 78 ms, after which it drops. Call dominant frequency is 2491 ± 129 Hz.

The call of P. beka sp. nov. can be distinguished from those of P. cooperi , P. amharensis , P. doro sp. nov., and P. neumanni (type A and B) by the distinguishable pulses composing the calls. It is also distinct from the calls of P. delphina sp. nov. and P. robeensis sp. nov. by its short inter-pulse intervals. The call of P. beka sp. nov. differs from the calls of P. delphina sp. nov., P. erlangeri , P. levenorum , and P. goweri by its higher dominant frequency. Finally, the call of P. beka sp. nov. differs from the call of P. nana and P. erlangeri by its longer duration.

Figures

Figure 18. Ptychadena beka sp. nov. A live male holotype (SB 291; left) and female paratype (SB 270, right) B dorsal and ventral views of the same individuals (male left, female right) after euthanasia and before fixation.