Friday, March 16, 2018

[Herpetology • 2018] Gephyromantis lomorina • A Distinctive New Frog Species (Anura, Mantellidae) supports the Biogeographic Linkage of Two Montane Rainforest Massifs in northern Madagascar

Gephyromantis (Vatomantis) lomorina 
Scherz, Hawlitschek, Razafindraibe, Megson, Ratsoavina, Rakotoarison, Bletz, Glaw & Vences, 2018

We describe a new species of the genus Gephyromantis, subgenus Gephyromantis Vatomantis (Mantellidae, Mantellinae), from moderately high elevation (1164–1394 m a.s.l.) on the Marojejy, Sorata, and Andravory Massifs in northern Madagascar. The new species, Gephyromantis (Vatomantis) lomorina sp. n. is highly distinct from all other species, and was immediately recognisable as an undescribed taxon upon its discovery. It is characterised by a granular, mottled black and green skin, reddish eyes, paired subgular vocal sacs of partly white colour, bulbous femoral glands present only in males and consisting of three large granules, white ventral spotting, and a unique, amplitude-modulated advertisement call consisting of a series of 24–29 rapid, quiet notes at a dominant frequency of 5124–5512 Hz. Genetically the species is also strongly distinct from its congeners, with uncorrected pairwise distances ≥10 % in a fragment of the mitochondrial 16S rRNA gene to all other nominal Gephyromantis species. A molecular phylogeny based on 16S sequences places it in a clade with species of the subgenera Laurentomantis and Vatomantis, and we assign it to the latter subgenus based on its morphological resemblance to members of Vatomantis. We discuss the biogeography of reptiles and amphibians across the massifs of northern Madagascar, the evidence for a strong link between Marojejy and Sorata, and the role of elevation in determining community sharing across this landscape.

Key Words: Bioacoustics, Biogeography, Marojejy, Montane Endemism, Sorata, Taxonomy

Figure 2. The holotype of Gephyromantis lomorina sp. n., ZSM 419/2016 (ZCMV 15221) in life.
(a) Dorsal; (b) ventral; and (c) dorsolateral view. Scale bars indicate 5 mm. 

Gephyromantis (Vatomantis) lomorina sp. n. 

Diagnosis: A species assigned to the genus Gephyromantis on the basis of its granular skin, moderately enlarged finger tips, small femoral glands consisting of a small number of large granules and present in males only (thus of type 2 as defined by Glaw et al. 2000), and bifid tongue. Within the genus Gephyromantis, assigned to the subgenus Vatomantis on the basis of its small size, connected lateral metatarsalia, absence of an outer metatarsal tubercle, paired subgular vocal sacs of partly whitish colour, greenish skin colouration, and riparian ecology. Gephyromantis lomorina sp. n. is characterized by the possession of the following suite of morphological characters: (1) granular skin, (2) reddish eyes, (3) mottled green and black skin, (4) males with paired subgular vocal sacs of partly white colour, (5) males with bulbous type 2 femoral glands consisting of a small number (2–3) of large granules, (6) white spots on the venter, (7) SVL 20.2–25.5 mm, and (8) fourth finger much longer than second. Furthermore, the species is characterised by distinctive, 1681–1827 ms advertisement calls of relatively low intensity, consisting of 24–30 individual pulsed notes, with 2–4 pulses per note, an inter-note interval of 41–75 ms, and a dominant frequency of 5124–5555 Hz. DNA sequence data from the 16S gene fragment supports the high divergence of this taxon to all other Gephyromantis, and is in agreement with its subgeneric assignment, albeit without statistical support (Fig. 1).

Etymology: The specific epithet is the Malagasy word lomorina, meaning ‘covered in moss’, in reference to the green, mossy appearance of the species in life. It is used as an invariable noun in apposition to the genus name.

Available names: There are no other, earlier names currently available (e.g., junior synonyms) that are assignable to the subgenera Vatomantis or Laurentomantis and that could apply to the new species.

Distribution: The new species is known from three localities in northeastern Madagascar: (1) Marojejy National Park (type locality), (2) Sorata massif, and (3) Andravory massif (Fig. 6). All specimens were collected between 1164 and 1394 m a.s.l.
Natural history: Specimens were collected near mountain streams in pristine montane riparian rainforest (Fig. 4g). In Marojejy National Park they were encountered during and after light rain, sitting in inconspicuous locations, especially on the fronds of tree ferns, but also on other low vegetation, between a few centimetres and up to 2 m above the ground. Specimens in Sorata were found in similar positions during dry weather, in the days just before the beginning of the rainy season. Males called irregularly and softly (see the call description above). Population density in Marojejy was remarkably high, with around three or four individuals being found along a 10 m stretch of stream. The observed density in Sorata was lower, possibly due to the absence of rain during the observation period. The species occurred in close sympatry with a number of other mantellids, but only few of these (especially Mantidactylus aff. femoralis) were found in the same microhabitat. Several specimens from Marojejy had pinkish mites (probably of the genus Endotrombicula; see Wohltmann et al. 2007) embedded within translucent whitish pustules on the skin of their fingers, toes, and bodies. Nothing is known about the reproduction of this species, but the calling sites suggest an association with lotic water.

Figure 3. Morphological and chromatic variation among paratypes of Gephyromantis (Vatomantis) lomorina sp. n. from Marojejy in life.
 (a–b) ZSM 420/2016; (c–d) UADBA 60296; (e–f) UADBA 60295; and (g–h) ZSM 418/2016. Scale bars indicate 2 mm. 

Figure 4. Photographs of Gephyromantis (Vatomantis) lomorina sp. n. and its habitat in Sorata.
 (a,d) ZSM 1545/2012; (b,e) ZSM 1547/2012; and (c,f) ZSM 1549/2012, not to scale;
 (g) habitat where several specimens were found in Sorata, showing (h,i) the appearance of the species in situ whilst calling at night.

 Mark D. Scherz, Oliver Hawlitschek, Jary H. Razafindraibe, Steven Megson, Fanomezana Mihaja Ratsoavina, Andolalao Rakotoarison, Molly C. Bletz, Frank Glaw and Miguel Vences. 2018. A Distinctive New Frog Species (Anura, Mantellidae) supports the Biogeographic Linkage of Two Montane Rainforest Massifs in northern Madagascar. Zoosystematics and Evolution. 94(2); 247-261. DOI:  10.3897/zse.94.21037

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