Bioacoustics of Platypelis alticola

Redescription. The holotype of P. alticola has been described by Guibé (1974) and Blommers-Schlösser & Blanc (1991) . Because we could not reliably assess the sex of this specimen, we here provide a redescription based on a newly collected adult male specimen, ZSM 1657/2010 (ZCMV 12453), seen calling but call not recorded. Specimen in good state of preservation, some muscle tissue removed from right thigh, snout-vent length 36.8 mm . Body very slender; head slightly wider than long, wider than body; snout rounded in dorsal and lateral views; nostrils directed dorsolaterally, not protuberant, nearer to tip of snout than to eye; canthus rostralis indistinct; loreal region plain; tympanum distinct, 63% of eye diameter, with a distinctly recognizable, apparently transparent area below the tympanum on both sides; supratympanic fold indistinct, almost straight; tongue ovoid, not bifid or notched; maxillary teeth distinct; vomerine teeth distinctly recognizable as two round groups on a bony ark; choanae rounded. Forelimbs slender; subarticular tubercles single, flat, and relatively well recognizable on all fingers; outer metacarpal tubercle distinct, relatively large and flat; inner metacarpal tubercle large, forming distinct protuberance at base of first finger; hand almost without traces of webbing between fingers; fingers distinctly flattened and broad along entire length; relative length of fingers 1<2<4<3, fourth finger distinctly longer than second; finger discs distinctly enlarged, slightly triangular; nuptial pads absent. Hindlimbs slender; tibiotarsal articulation reaching forelimb insertion when hindlimb adpressed along body; tibia length, 33% of SVL; lateral metatarsalia strongly connected; inner and outer metatarsal tubercles small and flat, difficult to recognize; only traces of webbing between toes; subarticular tubercles on toes relatively well recognizable on left foot (right foot damaged); toes flattened and broad along their entire length; relative length of toes 1<2<5=3<4 (evaluated on left foot only). Dorsal skin smooth, without dorsolateral folds. Ventral skin smooth on throat and chest and moderately granular on belly. After two years in 70% ethanol, dorsum almost uniformly beige with a poorly delimited grey spot on neck and blackish skin above eyes. Forelimbs and hindlimbs dorsally uniformly beige to yellowish, without spots or crossbands. Ventrally, throat yellow with an elongated, greyish blotch of 2.5 mm length on each side of the jaw; chest yellowish without spots, belly, ventral parts of thighs and feet dirty white with small greyish dots. Variation and distribution. We found specimens that morphologically agree with P. a l t i c o l a at the three first campsites along the Maromokotro trail, as well as on a site between the fourth and fifth campsite, spanning an elevational range from 1589–2429 m a.s.l. Molecular data summarized in Fig. 7 indicate that the specimens from Camp 1 (Antevialambazaha), i.e. from the lowest elevation, are genetically differentiated from the genetically homogeneous group of samples from all other sites. In the 16S rDNA fragment analyzed here, their differentiation amounts to 3.8% uncorrected pairwise distance. The few specimens from Camp 1 were also remarkable by their relatively tubercular skin and a high prevalence of mite parasites, probably of the genus Endotrombicula ( Wohltmann et al. 2007 ) . Because of the low sample size and lack of bioacoustic data from the Antevialambazaha population the possible taxonomic distinctness of this population cannot be reliably assessed at present. All specimens encountered were uniformly greyish-brownish colored dorsally and ventrally. Summarizing data from field measurements and preserved specimens (Table 1), male SVL ranged from 34–37 mm and female SVL 36–45.5 mm , with a single (possibly immature) female measuring 32 mm . Habitat and natural history. At the Matsabory Maiky campsite in June 2010 , we observed P. alticola in bamboo segments with holes of 27.5 ± 7.7 mm ( 18.3–35.5 mm , N= 7) diameter and at 142 ± 95.4 cm ( 40–300 cm , N= 7) height above the ground. 1.7 ± 0.5 individuals (1–2, N= 10) were found occupying the same segment. Specimens cohabited segments with Platypelis tsaratananaensis or with small cockroaches; in fact, 7 individuals of the 10 collected from bamboo segments shared their segment with one or several cockroaches. Gravid females of P. alticola had a SVL of 41.7 ± 2.0 mm ( 40.5–45.5 mm , N= 7), and they carried 26.6 ± 8.5 (15–35, N= 7) oocytes as visible through the ventral skin. At Camp 3 (Bepia) we did not record any large bamboo stands; only bamboo trunks of low diameter were observed, many of which appeared to be young plants dead or dying, possibly because of adverse climate conditions as this site was exposed to rather strong wind. We also found numerous P. alticola on the ground, walking around in the grass at our campsite. Advertisement call. Platypelis alticola emits series of tonal single-note calls at night, with regular intervals between notes. Calls were typically emitted from relatively high positions in dense bamboo thicket, and calling males were thus difficult to locate. A single male specimen (ZSM 1657/2010 = ZCMV 12453) was seen calling and collected by T. Rajoafiarison (between 15–20 June 2010 ), but the calls of this specific animal were not recorded and our analysis below refers to a specimen that was not collected. However, because only two species of frogs called at Matsabory Maiky, the identification does not seem to be equivocal. The recording analyzed, from shortly after dusk on 13 June 2010 , ca. 19:00–20:00 h, air temperature about 13°C, includes a series of four notes within a total of 67 seconds. Call frequency spanned over a narrow frequency band which in one note analyzed in detail was 1765–1981 Hz, with a dominant frequency of 1894 Hz (all other notes recorded from this specimen had very similar frequency ranges). Characterizing a fundamental frequency in such a tonal note is difficult, but tentatively the lowest observed frequency (1765 Hz) might be considered as fundamental. Temporal call parameters were as follows: note length of single notes 411–466 milliseconds (445±26; N= 4); interval between two notes 3790–3913 milliseconds (3867±67; N= 3) ( Fig. 10 ).

Diagnosis and comparisons. Assigned to the genus Platypelis in the Cophylinae based on enlarged terminal discs on fingers and toes, absence of finger-like prepollex, absence of nuptial pads, occurrence in Madagascar , and molecular phylogenetic relationships. Distinguished from all other cophyline species with enlarged discs on fingers and toes (i.e., all Anodonthyla , Cophyla , Platypelis , as well as Plethodontohyla guentheri , P. inguinalis , P. mihanika , P. notosticta , Stumpffia helenae ) by combination of the following character states: large body size (adult SVL 32–45 mm ), uniform greyish color with absence of sharp border between dorsal and lateral color, toes 3 and 5 of similar length, vomerine teeth present, males with prepollical tubercle but lacking a finger-like prepollex as typical for Anodonthyla . Distinguished from other species of Platypelis and Cophyla as follows: From Cophyla berara , C. occultans , C. phyllodactyla , Platypelis barbouri , P. cowanii , P. mavomavo , P. milloti , P. pollicaris , P. ravus , and P. tetra by larger adult body size (SVL 32–45 mm vs. 16–30 mm ). Among these species, furthermore distinguished from P. milloti , P. ravus , and P. barbouri by the uniform dorsal side (vs. always with distinct pattern of dark dorsal markings), from P. barbouri and P. r a v u s by the presence of vomerine teeth (vs. absence); from P. barbouri , P. milloti , P. mavomavo , and P. ravus by always uniform greyish ventral side (vs. reddish or yellow color on venter and/or ventral side of hindlimbs); from P. tetra by absence of 4 to 6 symmetrical and light colored dorsal tubercles (vs. presence); from P. cowanii , P. mavomavo , and P. tetra by third and fifth toe of similar length (vs. third toe longer). Among species of similar or larger size, distinguished from P. grandis by usually smaller size (SVL 32–45 vs. 43–105 mm ), juveniles and adults uniformly greyish (vs. juveniles greenish and adults typically with dark brown pattern on grey), typically shorter hindlimbs (tibiotarsal articulation reaching forelimb insertion vs. reaching tympanum), and different advertisement call (series of tonal vs. non-tonal notes); from P. tsaratananaensis by usually larger body size (SVL 32–45 vs. 22–33 mm but typically below 30 mm ), third and fifth toe of similar length (vs. third toe distinctly shorter), and advertisement call (series of single notes vs. series of double notes); from P. tuberifera by shorter hindlimbs (tibiotarsal articulation reaching forelimb insertion vs. reaching tympanum or eye), absence of a vertebral stripe (vs. present in most specimens), living in bamboo habitat (vs. specialized to Pandanus leaf axils), non-frequency modulated notes in advertisement call (vs. frequency-modulated). Furthermore P. alticola has>10% uncorrected pairwise divergence (16S) from all other arboreal species of cophylines.