Mantidactylus alutus ( Peracca, 1893 )

Scherz, Mark D., Crottini, Angelica, Hutter, Carl R., Hildenbrand, Andrea, Andreone, Franco, Fulgence, Thio Rosin, Köhler, Gunther, Ndriantsoa, Serge Herilala, Ohler, Annemarie, Preick, Michaela, Rakotoarison, Andolalao, Rancilhac, Loïs, Raselimanana, Achille P., Riemann, Jana C., Rödel, Mark-Oliver, Rosa, Gonçalo M., Streicher, Jeffrey W., Vieites, David R., Köhler, Jörn, Hofreiter, Michael, Glaw, Frank & Vences, Miguel, 2022, An inordinate fondness for inconspicuous brown frogs: integration of phylogenomics, archival DNA analysis, morphology, and bioacoustics yields 24 new taxa in the subgenus Brygoomantis (genus Mantidactylus) from Madagascar, Megataxa 7 (2), pp. 113-311 : 170-178

Mantidactylus alutus ( Peracca, 1893)

Type material.— Rana aluta Peracca, 1893 is based on 25 syntypes according to the original description, 14 of the colour morph ‘forma’A and 11 of the ‘forma’ B.According to Frost (2021), Rana aluta Peracca, 1893 includes the following syntypes: MZUT An725 and An729 , MNHN 1894.1–2 , and specimens in BMNH, all from ‘dintorni di Andrangoloaka e dalla vicina valle dell’Umbi’ . However, Gavetti and Andreone (1993) designated MZUT An725.1 as lectotype and redescribed this specimen including morphological measurements (summarised in Table 4 ). They listed 11 paralectotypes of colour morph A ( MZUT An725.2–12 ) and 13 of colour morph B ( MZUT An729 ), resulting in a total of 25 type specimens, although their numbers of individuals attributed to both colour morphs differ from the original description ( Peracca 1893). However, since the total number of type specimens is in accordance with the number mentioned by Peracca (1893) the claim by Blommers-Schl̂sser and Blanc (1991) concerning the presence of two other syntypes at Paris ( MNHN 1894.1 and 1894.2 ) does not seem to be correct ( Gavetti & Andreone 1993: 106) and the same must be assumed for the specimens claimed by Boulenger (1895 ‘1894’) to have been received by the BMNH from Peracca. An additional non-type specimen is MZUT An917 from Andrangoloaka ( Gavetti & Andreone 1993), demonstrating that more than the 25 types were available in the MZUT collection. The MNHN and BMNH specimens are therefore not paralectotypes.

Identity.—In this study we obtained genetic data via barcode fishing from specimen MNHN 1894.1 from Andrangoloaka, marked as ‘type’ of M. alutus in the MNHN catalogue and provided by M.G. Peracca according to the MNHN catalogue, but, as discussed above, probably not representing one of the paralectotypes. The 16S sequence of this specimen clustered among specimens from the central highlands of Madagascar that are typically considered as M. alutus (BlommersSchl̂sser 1979; Blommers-Schl̂sser & Blanc 1991; Glaw & Vences 1992a, 1994, 2007). Although this information does not refer to the lectotype of the species, little doubts thus remain that the nomen M. alutus has been correctly applied to this small-sized lineage from the central highlands.

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Synonyms.— The taxon Mantidactylus laevis Angel, 1929 was listed as a dubious species by Guibé (1978) and considered a synonym of M. alutus by Glaw and Vences (1992a). The holotype MNHN 1929.208, collected by G. Petit from the vicinity of Antananarivo (type locality ‘environs de Tananarive’; SVL 32 mm according to the original description) was reported to be lost according to Guibé (1978), and this has been confirmed by S. Grosjean (pers. comm. to A. Ohler, 22 January 2022). Because M. alutus is the only species of Brygoomantis occurring in the Antananarivo area, little doubts remain that this synonymy is correct. In order to stabilize synonymies and as the holotype has been lost for more than 40 years, we here designate the lectotype of Rana aluta, MZUT An 725.1 as the neotype of Mantidactylus laevis Angel, 1929 .

Diagnosis.—A member of the M. curtus clade and sister to a monophyletic group of all other species of the clade. See Table 4 for a list of diagnostic morphological characters. The combination of relatively small body size of up to 31 mm, slightly granular skin with (weakly expressed) dorsolateral ridges, small tympanum diameter of ca 9% of SVL in males, absence of small white spots on flanks, presence of a light frenal stripe in most specimens, and advertisement calls as a regular series of short pulsed notes distinguishes M. alutus from species of the other clades. Within the M. curtus clade, M. ambohimitombi , M. bourgati and M. curtus have larger body sizes, and M. madecassus and M. pauliani are high-elevation endemics with usually a shorter snout and absence of dorsolateral ridges ( Table 4 ). For detailed distinction from new species described herein, see the respective species accounts. A full list of molecular diagnostic sites in the 16S gene of M. alutus in pairwise comparisons to all other Brygoomantis species is provided as Supplementary appendix.

Variation.—Variation in measurements is given in Table 5 . See Fig. 11 for colouration in life and its variation.

Some individuals have a light vertebral stripe. There is moderate sexual size dimorphism (confirmed male SVL 23.4–27.2 mm [n = 2] vs confirmed female SVL 31.0 mm [n = 2]). Males with large and distinct femoral glands (e.g. Fig. 11b ); in MNHN 1894.1 and 1894.2, FGL and FGW are 2.4 mm x 1.4 mm and 1.7 mm x 1.4 mm, respectively.

The glands can be of orange/yellow colour in some individuals in life (e.g. Fig. 11b ), which may be related to the reproductive state.

Natural history.— Typically found in slow-flowing parts of streams or associated swamps in Madagascar’s highlands. Often at the edge of forest or in streams devoid of forest, with some gallery vegetation only. Males call from the edge or very shallow parts of water, from concealed positions during the day or from more open positions at night. See Vences et al. (2002) for observations from Ankaratra. This species is also abundant in parks of Antananarivo, e.g. in the Tsimbazaza garden (Glaw & Vences 2007).

Calls.— The advertisement call of M. alutus , recorded on 21 January 2003, 17:30 h, near Antoetra, 20.5–21.0°C air temperature ( Vences et al. 2006: CD 2, track 61, cut 1), consists of a short, regularly pulsed note, emitted in series at regular intervals ( Fig. 12 ). Notes exhibit distinct amplitude modulation, with amplitude continuously increasing from the beginning, reaching maximum call energy at the middle of the note, before continuously decreasing towards the note’s end. Numerical parameters of eight analysed calls are as follows: call duration (= note duration) 149–290 ms (234.3 ± 53.5 ms); 20–27 pulses per note (24.1 ± 2.7); pulse duration 5–8 ms (6.3 ± 1.0 ms); pulse repetition rate within notes 83.3–130.4 pulses/s (108.2 ± 17.3); dominant frequency 1040–1116 Hz (1081 ± 26 Hz); prevalent bandwidth 600–4800 Hz; call repetition rate (= note repetition rate) within regular series ca 110 calls/min.

Calls recorded on 1 January 1994, 18:20 h, at Manjakatompo, 18°C air temperature ( Vences et al. 2006: CD 2, track 61, cut 2) generally agree in character with the calls described above. Calls of a series containing nine calls have the following parameters: call duration (= note duration) 254–310 ms (278.5 ± 16.8 ms); 21–27 pulses per note (23.7 ± 2.2); pulse duration 3–6 ms (4.9 ± 0.7 ms); pulse repetition rate within notes 66.7–120.0 pulses/s (83.2 ± 19.0); dominant frequency 1270–1378 Hz (1326 ± 45 Hz); prevalent bandwidth 800–5600 Hz; call repetition rate (= note repetition rate) within series ca 115 calls/min.

Tadpoles.—The tadpoles of M. alutus were described by Blommers-Schl̂sser (1979) and Schmidt et al. (2009).

Distribution.— Endemic to the central highlands of Madagascar ( Fig. 7 ). This species is known from Antananarivo, Ankaratra, Ibity, Ambohitantely, Ranomafanakely,Antoetra, a swamp in the Alaotra region, Mantasoa, Forêt de Tampina, and Tsinjoarivo. Elevation range: 933–2090 m a.s.l.

Etymology.— Probably derived from the Greek adjective ἄλουτος, meaning ‘unwashed’ or ‘speckled’, presumably in reference to the dorsal colour pattern.

Figures

FIGURE 7. Mantidactylus subgenus Brygoomantis species distribution based on verified records, divided by clade (Mantidactylus stelliger sp. nov. is presented alongside the inaudax clade for practicality). Colours for species correspond to those in Figs 2 and 4. Inset map shows the geographic regions of Madagascar identified by Boumans et al. (2007), referred to throughout the text.

FIGURE 11. Mantidactylus alutus in life, in dorsolateral and ventral view. (a,b) Adult male from near Lake Mantasoa (ZSM 355/2000), photographed in 2000. (c,d) Adult male from near Antoetra (probably ZMA 19550 = FGMV 2002.50), photographed in 2003. (e) Adult male from Manjakatompo, photographed in 1991. (f) Specimen from Antakasina (this specimen has not been sequenced and its identification is therefore tentative; the locality is thus not included in the species account).

FIGURE12.Audiospectrogramandcorresponding oscillogramoftwo advertisement calls froma regularcall seriesofMantidactylus alutus, recorded on 21 January 2003 near Antoetra (20.5–21.0°C air temperature). Recording highpass-filtered at 375 Hz.