Mantidactylus curtus ( Boulenger, 1882 )

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 : 166-170

Mantidactylus curtus ( Boulenger, 1882)

Type material.— Rana curta Boulenger, 1882 is based on seven syntypes, four of which are still available: BMNH 1947.2.10.28–31 from ‘ East Betsileo’ and ‘ Ankafana, Betsileo’ . We here designate the DNA-barcoded specimen BMNH 1947.2.10.30, probably an adult male (sex not unambiguously confirmed), as lectotype. In consequence, the type locality is now ‘ East Betsileo’ . Lectotype designation is justified by the need to stabilize this and other nomina in Brygoomantis , given the uncertain identity and morphological similarity of many taxa in the subgenus.

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Identity.—The name Mantidactylus curtus has been applied to a complex of genetically divergent lineages inhabiting various mountain ranges and areas of the central high plateau of Madagascar (e.g. Blommers-Schl̂sser & Blanc 1991; Glaw & Vences 1992a). Glaw and Vences (2006) revalidated M. bourgati to refer to the lineage of the Andringitra Massif, but the identity of M. curtus remained uncertain. We here provide a 16S sequence of the lectotype that clusters with a lineage from various localities not far from the type locality (e.g. Antoetra, Itremo, Col des Tapias), providing definitive evidence of the assignment of the nomen curtus to this lineage.

Evidence of introgression of genomic material from this species ( M. curtus ) into a syntopic lineage ( M. ambohimitombi marefo ssp. nov., described below) was found in the Phylonetworks analysis ( Fig. 5 ). Since the latter taxon appears to have a limited distribution range in the Itremo Massif, and the observed reticulation only concerned one M. curtus specimen from the same site, it is likely that this inter-species gene flow is localized and does not compromise the identity of M. curtus as independently evolving lineage.

Synonyms.—Boulenger (1895) considered Rana inaudax Peracca, 1893 to be a synonym of M. curtus , but that species name is revalidated below.

Diagnosis.— A member of the M. curtus clade and sister to M. bourgati . See Table 4 for a list of diagnostic morphological characters. The combination of relatively large body size of up to 39 mm, smooth skin, absence of dorsolateral ridges, strongly developed foot webbing with fully webbed fifth toe, and relatively short snout distinguishes this species from species of the other clades.

Within the M. curtus clade, M. alutus , M. madecassus and M. pauliani have smaller body sizes ( Table 4 ).

Mantidactylus curtus has smooth dorsal skin, constituting a difference to many specimens of M. ambohimitombi and M. bourgati where the skin is somewhat granular.As far as known, M. curtus and its sister species M. bourgati occur allopatrically and therefore can be distinguished based on localities. 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. curtus in pairwise comparisons to all other Brygoomantis species is provided as Supplementary appendix.

Variation.—Variation in measurements is given in Table 5 . See Fig. 10 for colouration in life and its variation.

Evidence for sexual size dimorphism is inconclusive (confirmed male SVL 33.7 mm [n = 1] vs confirmed female SVL 32.5–39.8 mm [n = 8]). In the male specimen MRSN A6757, FGL x FGW is 5.6 mm x 2.6 mm. In many other individuals, femoral glands are less distinct, and some of them cannot be reliably sexed by external examination.

Natural history.— Specimens were found in the vicinity of highland streams, usually quite close to the water.

Calls.—The call of this species has not been recorded.

Tadpoles. —A tadpole of M. curtus (ZSM 943/2004) was described by Schmidt et al. (2009). The tadpole description by Blommers-Schl̂sser (1979), based on materialfromManjakatompo(Ankaratra) andAngavokely, probably refers to different species, as M. curtus is not among the species we have recorded from Ankaratra here. We have not re-sampled Angavokely, but M. alutus and M. ambohimitombi miloko ssp. nov. occur at sites nearby, the latter of which closely resembles M. curtus .

Distribution.— Endemic to a small area of the central highlands of Madagascar ( Fig. 7 ). This species is known from Ambositra, Ankazomivady, Antoetra, Antsirakambiaty forest, Col des Tapias, Ibity, Itremo, and Vatolampy. Elevation range: 1300–2090 m a.s.l.

Etymology.— Latin adjective meaning ‘shortened’ or ‘short’, presumably in reference to the short snout of the species.

Figures

FIGURE 5. Maximum-Likelihood tree based on a partitioned analysis of 12,818 nuclear-encoded markers obtained via the FrogCap strategy, calculated with IQ-tree, for 58 representative individuals of species-level lineages in the subgenus Mantidactylus (Brygoomantis). Note that three species are missing from this analysis (M. bletzae sp. nov., M. marintsoai sp. nov., and M. riparius sp. nov.) and the identity of the two samples of M. katae sp. nov. in this tree is uncertain. For those lineages that previously (Perl et al. 2014; Vieites et al. 2009) had candidate species numbers assigned, these are reported in parenthesis after the name used in the classification proposed herein. All branches were fully supported by SH-like approximate likelihood ratio tests with 1000 pseudoreplicates (100% support, symbolized by black dots at nodes).The tree was rooted with Mantidactylus grandidieri (subgenus Mantidactylus) as outgroup (removed from graphical representation for better visualization of ingroup relationships), with the inclusion of M. melanopleura (subgenus Chonomantis) as hierarchical outgroup. Red arrows in the M. curtus clade indicate the two reticulation events detected by a Phylonetworks analysis performed separately for this clade (note that the topology recovered by this analysis in the Phylonetworks analysis differs in the position of M. bourgati; see original results of the Phylonetworks analysis in Zenodo repository, DOI 10.5281/zenodo.668741

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 10. Mantidactylus curtus in life, in dorsolateral and ventral view. (a,b) Female specimen (ZSM 768/2001 = FGMV 2001.489) from Itremo, photographed in 2001 (note the almost complete absence of femoral glands). (c,d) Probable female (note small femoral glands) from Antoetra, photographed in 2003. (e,f), Probable female (ZSM 758/2001 = FGMV 2001.423; note rather small femoral glands) from Mount Ibity/Col des Tapias, photographed in 2001.