Gephyromantis (Duboimantis) grosjeani, D. & Mihaja, 2018

D., Mark & Mihaja, Fanomezana, 2018, Two new Madagascan frog species of the Gephyromantis (Duboimantis) tandroka complex from northern Madagascar, Alytes 36 (1 - 4), pp. 130-158 : 146-152

Gephyromantis (Duboimantis) grosjeani sp. nov.

( fig. 1–3 , 5–9 , Table 1)

LSID: urn:lsid:zoobank.org:act:

Gephyromantis (Duboimantis) sp. Ca32 – ( Scherz et al. 2017 a)

Specimens allocated to new species

Holotype

ZSM 1554/2012 ( FGZC 3584 ), an adult male collected at high elevation on the Sorata massif (13.67– 13.69°S, 49.43– 49.44°E, ca. 1400–1500 m a.s.l.), District de Vohemar, Région Sava, northern Madagascar, at night on 26 November 2012 by F. Glaw, O. Hawlitschek, T. Rajoafiarison, A. Rakotoarison, F. M. Ratsoavina and A. Razafimanantsoa.

Paratypes

ZSM 1555/2012 ( FGZC 3585 ) and UADBA uncatalogued ( FGZC 3583 ), two adult females and UADBA uncatalogued ( FGZC 3599 ), an adult male with the same collection data as the holotype. ZSM 1553/2012 ( FGZC 3749 ), a male, ZSM 1552/2012 ( FGZC 3693 ), a female and UADBA uncatalogued ( FGZC 3690 ), an unsexed individual, collected in bamboo forest above the campsite in Sorata (ca. 13.6752°S, ca. 49.4410°E, ca. 1485 m a.s.l.), District de Vohemar, Région Sava, northern Madagascar, at night between 28–30 November 2012 by F. Glaw, O. Hawlitschek, T. Rajoafiarison, A. Rakotoarison, F. M. Ratsoavina and A. Razafimanantsoa. UADBA uncatalogued ( FGZC 3598 ), an adult male collected above the campsite in Sorata ( 13.6829°S, 49.4419°E, 1312 m a.s.l.), District de Vohemar, Région Sava, northern Madagascar, at night on 26 November 2012 by F. Glaw, O. Hawlitschek, T. Rajoafiarison, A. Rakotoarison, F. M. Ratsoavina and A. Razafimanantsoa.

Diagnosis

A Gephyromantis species assigned to the subgenus Duboimantis on the basis of its fairly smooth skin, interocular tubercles generally present, moderately large body size and presence of inner and outer dorsolateral folds. Gephyromantis grosjeani is characterised by the following unique suite of characters: (1) large body size ( 36.1–38.4 mm in adult males, 40.8–41.0 mm in adult females), (2) paired subgular vocal sacs, (3) HIL/SVL 1.84–2.03, (4) TD/ED 0.53–0.59, (5) presence of inner and outer dorsolateral folds, with the inner folds being generally weak, (6) reticulated low ridges on the dorsum, (7) large, distinct femoral glands in males consisting of 25–41 granules. It is furthermore characterised by advertisement calls consisting of pulsatile single-note calls arranged in undefined series.

Comparisons

Within the genus Gephyromantis , G. grosjeani may be distinguished from all members of the subgenus Gephyromantis on the basis of larger body size (SVL 36.1– 41.0 mm vs. 20–33 mm); from all members of the subgenus Asperomantis by less rough dorsal skin, less distinct inner dorsolateral ridges, less pronounced supraocular spines and absence of a pale spot in the middle of the tympanum; from all members of the subgenus Phylacomantis on the basis of the presence of distinct dorsolateral ridges (vs. absent or discontinuous), more slender body shape and absence of outer metatarsal tubercle (vs. presence); from all members of the subgenus Laurentomantis on the basis of larger body size (SVL 36.1–41.0 mm vs. 20–34 mm), smooth skin (vs. highly granular to rugose); and from all members of the subgenus Vatomantis on the basis of much larger body size (SVL 36.1–41.0 mm vs. 23–31 mm), lack of greenish skin colouration (vs. presence) and less slender limbs. Within the subgenus Duboimantis , it may be distinguished from all species except G. (D.) salegy , G. (D.) redimitus , G. (D.) plicifer and G. (D.) moseri by larger and/or more distinct femoral glands in males. Additionally, it may be distinguished from G. (D.) cornutus and G. (D.) redimitus by the possession of paired subgular vocal sacs (vs. single); from G. (D.) luteus , G. (D.) sculpturatus and G. (D.) plicifer by less webbed toes, lack of concave black suprascapular markings (vs. usually present) and presence of only diminutive heel spines (vs. distinct heel spines); from G. (D.) moseri by the much less rugose dorsum and smaller supraocular tubercles; from G. (D.) salegy and G. (D.) redimitus by much smaller body size (SVL 36.1–41.0 mm vs. 46–53 mm); from G. (D.) saturnini by smaller adult male body size ( 36.1–38.4 mm vs. 39.4–42.8 mm) and less distinct inner dorsolateral folds; from G. (D.) schilfi , G. (D.) tschenki and G. (D). tohatra by larger body size (SVL 36.1–41.0 mm vs. 27–36 mm); from G. (D.) zavona , G. (D.) leucomaculatus and G. (D.) granulatus by the general presence of interocular tubercles (vs. absence). From the highly similar G. (D.) tandroka , it may be distinguished most reliably by the distinct femoral glands in males ( fig. 6 ) and provisionally (due to low sample sizes) males may differ by slightly longer relative foot length (FOL/SVL 0.58– 0.59 vs. 0.51–0.57) and females may differ by slightly longer relative forelimb length (FORL/SVL 0.62–0.63 vs. 0.64–69). The interocular spines of this species appear to be smaller and less distinct than those of G. tandroka , even when they are present ( fig. 7 ).

Genetically, the species is distinguished from all other species of Gephyromantis by uncorrected p-distances of at least 5.1 % in the analysed 16S rRNA gene fragment.

The calls of G. (D.) grosjeani strongly resemble those of G. (D.) tandroka , but differ slightly in call duration (119–128 ms vs. 77–94 ms) and inter-call interval duration (1977–2720 ms vs. 1524–2034 ms), but the assessment of the diagnostic value of these differences requires additional data.

Description of holotype ZSM 1554/2012, adult male

Specimen in a good state of preservation, a tissue sample taken from the left thigh. SVL 38.4 mm. For other measurements see Table 1. Body somewhat gracile; head longer than wide, not as wide as body (body is somewhat inflated in preservative); snout pointed in dorsal view, rounded in lateral view; nostrils directed laterally, protruding slightly, much nearer to tip of snout than to eye; canthus rostralis distinct, straight; loreal region concave and weakly oblique; tympanum indistinct, oval, its horizontal diameter 58 % of eye diameter; supratympanic fold distinct, curved, from the posterior corner of the eye to above the insertion of the arm; tongue fairly narrow, posteriorly bifid; vomerine teeth clearly distinct, arranged in two small aggregations on either side of the midline of the palate at the level of the anterior edge of the eye, posteromedial to choanae; choanae small and rounded and laterally displaced. Pigmented translucent dermal fold below each jaw starting at the level of the anterior edge of the eye. Arms quite stocky, subarticular tubercles single, highly distinct; outer metacarpal tubercle small and oval and inner metacarpal tubercle relatively well developed; fingers without webbing; relative length of fingers 1 <2 <4 <3, second finger distinctly shorter than fourth; finger discs distinctly enlarged, round, nuptial pads absent. Hindlimbs slender; lateral metatarsalia separated distally with webbing; subarticular tubercles highly distinct; inner metatarsal tubercle distinct, anteriorly oriented, outer metatarsal tubercle absent; webbing formula of foot according to the scheme of Blommers-Schlösser (1979) 1(1), 2i(1.5), 2e(1), 3i(2), 3e(1.5), 4i(2.75), 4e(2.5), 5(1); relative toe length 1 <2 <3 = 5 <4, third toe equal in length to fifth; toe discs distinctly enlarged. Skin dorsally smooth, with one pair of distinct dorsolateral ridges running from the suprascapular region to the hip, and weak suggestion of a pair of inner dorsolateral ridges as termed by Vences & Glaw (2001) only over the suprascapular region; interocular spines absent; two diminutive supraocular spines present; a diminutive dermal flap is present on the heel; skin smooth on chin, forelimbs and hindlimbs ventrally, but highly granular on the abdomen and lower flanks. Femoral glands distinct, large, type 2 sensu Glaw et al. (2000), 8.1 mm long, 3.6 mm wide (measured in external view), consisting of 37 granules on the right thigh and 31 on the left thigh (counted in internal view).

The colouration in life is unknown. After six years in preservative ( fig. 5 ), the dorsum is grey-beige fading through salmon laterally onto grey flanks; the outer dorsolateral folds are cream. The lateral head is distinctly different in colour from the dorsum, with burnt umber patches over the tympanum, under the eye, along the canthus rostralis and around the nostril, separated by cream patches. The forelimb is cream in base-colour with thin blackish markings along the posterior edge of the upper forelimb, with salmon-grey crossbands with blackish internal markings from the hand to the elbow. The dorsal surface of the hand is externally the same salmon-grey colour, and internally cream. The dorsal hindlimb is light salmon in base colour with numerous mauve crossbands dorsally that darken to nearly black on the leading and trailing edges; there are roughly seven crossbands on the thigh, four or five on the shank and five becoming more indistinct on the foot; the toes lack crossbands. The hidden surfaces of the posterior thigh are a coffee brown towards the knee, becoming dappled with cream toward the cloaca, with a poorly-defined dark brown trapezoid below the cloaca. The ventral base colour is cream, immaculate over the abdomen and ventral surfaces of the forelimbs, but dappled with dark brown on the chin. The ventral surfaces of the hands and feet are a muddy grey. The thighs are cream with irregular small light brown spots all over except on the femoral glands ventrally, which are cream.

Morphological and chromatic variation

In morphology, the paratypes strongly resemble the holotype; for variation in measurements, see Table 1. Females are apparently larger than males (40.8–41.0 mm vs. 36.1–38.4 mm in males), but no other sexual dimorphisms are visible except the absence of the distinct femoral glands in females. Males have clearly bilobed subgular vocal sacs ( fig. 8 ) The distinctiveness of the inner dorsolateral folds is variable, being distinct in ZSM 1552/2012, but weak or almost absent in the other specimens examined. Interocular tubercle presence is variable: present in ZSM 1552/2012 and 1553/2012, but absent in the holotype and ZSM 1555/2012 ( fig. 7 ). The strength of the supraocular tubercles is slightly less variable, being small in all specimens, but exceptionally so in ZSM 1555/2012. Femoral glands vary in the number of granules (25–41) and the shape of the gland ( fig. 6 & 9 ); the glands of ZSM 1553/2012 measure 5.4 mm long by 2.7 mm wide.

The dorsal colouration of this species is highly variable ( fig. 9 ), while the ventral colouration is largely consistent, even between males and females except that the females lack the different colouration of the vocal sacs present in males. Dorsal base-colour ranges from the beige to salmon of the holotype to dark brown in preservative. The outer dorsolateral folds can be distinctly cream as in the holotype, or indistinct in colour as in ZSM 1552/2012. ZSM 1555/2012 differs dramatically in body colouration in having a strong colour border on the whole body between the dark brown dorsum and the light cream flanks. Laterally, the head can be solid black above with a white lip (e.g. ZSM 1553/2012) or wholly cream with only dark brown on the tympanum (ZSM 1555/2012). The number of crossbands on the limbs is wholly variable. When present, interocular tubercles are surrounded with blackish circles.

Bioacoustics

The advertisement call, recorded on 29 November 2012 at 20 h 30 at an elevation of ca. 1400 m a.s.l. in moderately disturbed primary montane forest (air temperature not recorded), consists of a single pulsatile note, with a call (= note) duration of 119–128 ms (121 ± 4 ms; N = 10 calls of one male), repeated for long periods with regular inter-call intervals of a duration of 1977–2720 ms (2363 ± 226 ms; N = 10). Each call (or note) consists of approximately 23–25 indistinct pulses (23.9 ± 0.7; N = 10), without clear silent interval between them. Pulse intensity decreases towards the end of the call, and pulses appear longer and more densely packed in the beginning of the call, becoming more distinct and more widely spaced toward the end. Dominant frequency is between 2713–3186 Hz (2936 ± 120 Hz; N = 10). Approximate prevalent bandwidth is between 1200–5800 Hz.

Natural history and conservation status

Numerous male individuals were heard calling at night at the end of November, sitting on branches and leaves, especially of ferns, in disturbed primary rainforest and bamboo forest, ca. 1–3 m above the ground at an elevation of ca. 1300–1500 m a.s.l., but we suspect that the species will be distributed more widely in the poorly surveyed Sorata and Andravory regions and perhaps other high-altitude rainforests in northern Madagascar. Similarly to G. saturnini sp. nov. described above, an evaluation of the conservation status of G. grosjeani sp. nov. based on current knowledge is liable to dramatically overestimate its threat status: at present it qualifies as Critically Endangered under IUCN (2012) criterion B1ab(iii) due to its range of below 100 km 2 (B1) from essentially one threat-defined location (a) undergoing relative dramatic decline in extent and quality of its habitats (b[iii]). To avoid being inflationary, we recommend that the species be considered Data Deficient until further survey work has been conducted in surrounding rainforest areas.

Etymology

We dedicate this species to Stéphane Grosjean, who completed his PhD studies under the mentorship of Alain Dubois, in recognition of his valuable contributions to the knowledge of Madagascan frog larvae (e.g. Grosjean et al. 2007, 2011 a, b).

Figures

Figure 1. Maximum Likelihood tree based on 1106 bp of the mitochondrial 12S and 16S rRNA gene fragments, showing phylogenetic relationships of the two new species to their closest relatives among Gephyromantis. Support values at nodes are ML likelihood bootstrap values and BI posterior probabilities. Gephyromantis granulatus was used as outgroup (removed for better graphical representation). Inset photos show representative individuals of the target species, size of the pictures roughly to scale.

Figure 2. Comparative oscillograms of parts of call series of some representative of the G. tandroka complex in the subgenus Duboimantis. The figure shows the typical pattern of multi-note calls in Gephyromantis (Duboimantis) saturnini sp. nov. vs. G. (D.) tandroka and G. (D.) grosjeani sp. nov. The recording of G. tandroka from 2005 (taken from Vences et al. 2006) is of a chorus of multiple specimens; for visualization, the amplitude of calls of other specimens was strongly reduced to highlight the calls of the specimens closest to the microphone.

Figure 3. Comparative spectrograms and oscillograms of calls of some representatives of the G. tandroka complex in the subgenus Duboimantis.

Figure 5. Holotypes of Gephyromantis (Duboimantis) saturnini sp. nov. (ZSM 61/2016) and G. (D.) grosjeani sp. nov. (ZSM 1554/2012) in dorsal (left) and ventral (right) view.

Figure 6. Femoral glands of male specimens of Gephyromantis tandroka ZSM 321/2005 (FGZC 2812), femoral gland granules (FGG) 24 left/21 right (above), G. saturnini sp. nov. Holotype ZSM 61/2016 (MSZC 123), FGG 16/15 (middle) and G. grosjeani sp. nov. (unidentified UADBA specimen), FGG, 41/34 (below). Note the much more distinct glands in the latter species.

Figure 7. Heads of Gephyromantis (Duboimantis) saturnini sp. nov. and G. (D.) grosjeani sp. nov. in dorsal view compared to G. (D.) tandroka. Arrows indicate the interocular tubercles, which appear less expressed especially in G. (D.) saturnini sp. nov. than in G. (D.) tandroka.

Figure 8. A calling male specimen of Gephyromantis (Duboimantis) grosjeani sp. nov. (specimen unidentified). Note the clearly bilobed subgular vocal sacs.

Figure 9. Photos in life of four specimens of Gephyromantis (Duboimantis) grosjeani sp. nov. from Sorata. (a–f) unidentified males (UADBA-A specimens) with femoral gland granule (FGG) numbers of (b) 41 left/34 right, (d) 31/34 and (f) 25/27; (g–h) female ZSM 1552/2012 (FGZC 3693).