Monday, April 27, 2020

[Herpetology • 2020] Platypelis ranjomena • Genetic Variability and Partial Integrative Revision of Platypelis Frogs (Microhylidae) with Red Flash Marks from eastern Madagascar

 Platypelis ranjomena
Glaw, Scherz, Rakotoarison, Crottini, Raselimanana, Andreone, Köhler & Vences, 2020

We studied the genetic variability of Platypelis species (Anura: Microhylidae) with red fash marks from Madagascar based on mitochondrial (16S rRNA) and nuclear (RAG1) genes. Our molecular phylogenetic results suggest that the red colour evolved independently in the Platypelis barbouri complex and P. milloti and confrm the validity of a long-known but still undescribed new species from eastern Madagascar. Platypelis ranjomena sp. nov. is distinctly coloured with dark red to purple patches at the base of the forelimbs, in the inguinal region, and on the ventral parts of the hind limbs. It differs from most other arboreal cophylines by this red colour and from its sister species P. barbouri by smooth dorsal skin texture, iris colour, bioacoustics (much longer note duration in advertisement calls), and genetics (strong differences in mitochondrial and nuclear markers). The new species is widespread at low elevations along the east coast from Marojejy in the north to Manombo in the south. However, genetic evidence indicates substantial intraspecifc variability among populations, suggesting that the taxonomy of P. ranjomena and the other species in this complex is still incompletely resolved. An individual of P. barbouri from Mahasoa shared a nuclear allele with P. ranjomena, and its call was to some degree intermediate between these species, suggesting a possible case of hybridization in an area that we hypothesize could be a contact zone between the two species. Individuals from Madagascar’s northeast hitherto assigned to P. barbouri represent a lineage that is sister to the clade of P. barbouri + P. ranjomena. It is herein identifed as a new candidate species (Platypelis sp. Ca11), which occurs in syntopy with P. ranjomena. 

Key words Amphibia; Anura; colouration; Cophylinae; Madagascar; molecular genetics; new species; Platypelis ranjomena; systematics.

Fig. 3.  Platypelis ranjomena sp. nov. in life in dorsolateral (left) and ventral (right) views:
(a, b) adult male holotype ZSM 407/2010 from Ambodivoangy; (c, d) adult male paratype ZSM 406/2010 from Ambodivoangy; (e, f) adult male paratype ZFMK 59908 from Marojejy; (g, h) adult male specimen ZSM 2421/2007 from Manombo, provisionally assigned to this species.

Platypelis ranjomena sp. nov.

Diagnosis: A medium-sized arboreal cophyline frog, SVL 24.1–28.8 mm, tips of fngers and toes well expanded, third toe slightly shorter than ffth, hind limbs relatively short (tibiotarsal articulation reaching the tympanum), vomerine teeth absent (not recognisable when examining the oral cavity), tympanum small and poorly recognisable, dorsal skin smooth, belly reddish and yellowish with intensely dark red areas in the axilla, inguinal region, and on ventral parts of shanks. 

Etymology: The specifc epithet is derived from the Malagasy words ‘ranjo’ (= leg) and ‘mena’ (= red). It is used as a noun in the nominative singular, standing in apposition to the generic name.

Distribution: The distribution based on genetically confrmed locality records is shown in Figure 2 and indicates that the species is widespread in the lowlands of eastern and north-eastern Madagascar. Additional unconfrmed locality records based on photographs and non-sequenced voucher specimens include the coast of Masoala (near ‘Eco-Lodge chez Arol’, ..., ca. 21 m a.s.l.), Ambodiriana (...), and near Analalava (..., ca. 30 m a.s.l.) close to Foulpointe (= Mahavelona). The Manombo population deserves further study as it may represent a deep conspecifc lineage or (less likely) a more divergent form. 

Fig. 7.  Platypelis ranjomena sp. nov. in situ in Ambodivoangy, the type locality.
 (a) Individual of Platypelis ranjomena sp. nov. in life, as discovered in leaf axil of a banana-like plant at the type locality; (b) same leaf axil showing three adult individuals of Platypelis ranjomena sp. nov. together with freshly laid eggs; (c) semi-open habitat within rainforest in Ambodivoangy.

Available names: Several junior synonyms in the genus Platypelis must be excluded as available names for P. ranjomena. Platyhyla verrucosa Mocquard, 1901 and Platyhyla voeltzkowi Boettger, 1913 (both junior synonyms of P. grandis according to Noble & Parker, 1926) are larger, have a granular dorsal skin and completely lack any red ventral colour; Cophyla tuberculata Ahl, 1929, considered a further synonym of P. grandis based on the comparison of juveniles (Blommers-Schlösser & Blanc, 1991), has granular skin and differs in colour pattern (Ahl, 1929); Paracophyla tuberculata Millot & Guibé, 1951, currently considered a junior synonym of P. barbouri (Blommers-Schlösser & Blanc, 1991), has a similar dorsal pattern to P. ranjomena (see Guibé, 1978: Fig. 348) and no vomerine teeth but is very small (SVL 17 mm) and has distinct dorsal tubercles, which are absent in P. ranjomena. The holotype of Platypelis barbouri is a gravid female of 20 mm SVL with large ovary eggs of 1.5 mm diameter and rugose skin (Noble, 1940) and thus smaller and more rough-skinned than P. ranjomena. 

New candidate species: (Platypelis sp. Ca11) Our genetic analysis revealed a deep new lineage in this species group that was not previously recognised (Fig. 1): specimens hitherto assigned to P. barbouri from Marojejy closely resemble that species and in fact represent a lineage that is sister to the P. barbouri + P. ranjomena clade, herein named P. sp. Ca11 (Fig. 8). This lineage also occurs in Ambolokopatrika, and at Ambodivoangy in syntopy with P. ranjomena (Figs 1–2). We are confident that the assignment of the name P. barbouri should be attributed to the southern lineage, as the type locality of Fanovana Forest is located close to Andasibe in central eastern Madagascar. This therefore represents a new candidate species that should be taxonomically investigated in the future; we have here refrained from doing so, as insufficient material was available to us for examination.

Frank Glaw, Mark D. Scherz, Andolalao Rakotoarison, Angelica Crottini, Achille P. Raselimanana, Franco Andreone, Jörn Köhler and Miguel Vences. 2020. Genetic Variability and Partial Integrative Revision of Platypelis frogs (Microhylidae) with Red Flash Marks from eastern Madagascar. Vertebrate Zoology. 70(2); 141–156. DOI: 10.26049/VZ70-2-2020-04