Bioacoustics of Mantidactylus ambohimitombi

Description of the holotype .—Adult male in good state of preservation ( Fig. 9 ). Tissue sample taken ventrally from right thigh. Femoral gland partly detached to examine their structure internally. Body rather slender. Head slightly wider than body. Snout rounded in dorsal and lateral view. Nostrils directed dorsolaterally, slightly protuberant. Nostrils nearer to tip of the snout than to eye. Canthus rostralis almost not recognisable, slightly concave. Loreal region slightly concave. Tympanum distinct, elliptical, wider than high, its diameter 78% of eye diameter. Supratympanic fold distinct, beginning straight, with a distinct, angular 90° bend at the posterior edge of tympanum towards insertion of forelimb. Tongue ovoid, distinctly posteriorly bifid. Maxillary teeth present. Vomerine teeth distinct in rounded aggregations, positioned posterolateral to choanae. Choanae rounded. Subarticular tubercles single. Outer metacarpal tubercle present, inner metacarpal tubercle present. Fingers without webbing. Relative length of fingers: I=II<IV<III. Finger discs minimally enlarged. Nuptial pads absent. Foot longer than tibia (113%). Lateral metatarsalia separated. Inner metatarsal tubercle present. Outer metatarsal tubercle small but recognisable. Webbing formula: 1(0.25), 2i(1), 2e(0.5), 3i(1.5), 3e(1), 4i(2), 4e(2), 5(0.75). Relative length of toes: I<II<V=III<IV. Skin on the upper surface smooth, with some granules on flanks, and some longitudinal tubercles forming interrupted and weakly expressed dorsolateral folds.Ventral side smooth. Femoral glands distinct but relatively small, with a distal ulcerous macrogland consisting of at least eight large granules and an external central depression, and a weakly expressed proximal granular gland field visible in internal view. Colour in preservative: light brown dorsally with large and contrasted dark brown patches all over the dorsal surface, distinct dark crossbands on limbs, and a light frenal stripe with some dark markings on the upper lip. Ventrally uniformly light grey with alternating dark-light pattern ventrally on the lower lip. Colour in life similar to that in preservative, but more contrasted ( Fig. 16 ). Variation. —Variation in measurements is given in Table 5 . Too few specimens have been sexed to assess the degree of sexual size dimorphism. Femoral glands distinct and large (but not differing in colour from surrounding ventral skin of thigh) in the male holotype ( Fig. 16 ). In contrast, specimens from the ZMA collection are difficult to sex externally as femoral glands are often indistinct, as seems to be typical for several taxa in the M. curtus clade, possibly due to seasonal effects. Natural history.— Specimens were collected around clean highland streams running in open areas between forest fragments. Specimens at Angavokely and Ankazomivady that appear to belong to this taxon based on mitochondrial DNA were found on wet rocks along slow-moving parts of streams. Calls .—The call of this subspecies has not been recorded. Tadpoles.— Probably reported from Angavokely by Blommers-Schl̂sser (1979)..

Identity and justification .—This lineage has been considered as confirmed candidate species M. sp. 20 by Vieites et al. (2009) and M. sp. Ca20 by Perl et al. (2014) . It was depicted as ‘ Mantidactylus sp. aff. pauliani “Itremo”’ by Glaw and Vences (2007) . It has been collected only at its type locality, Itremo. It is characterized by rather aquatic habits and a morphology reminiscent of M. pauliani , with a short and rounded snout as in that species. Its mitochondrial DNA is near-identical to that of the nominal lineage, M. a. ambohimitombi (0.6–1.0 % pdistance) which, however, is morphologically distinct and also differs in Rag-1 haplotypes. Our phylogenomic tree confirms close relationships between this lineage and the one from Ankaratra, and for now we therefore consider a status of subspecies as adequate for the Itremo lineage, especially given that very little is known about its biology, since both its tadpoles and calls are unknown.

Calls.— The advertisement call of M. a. ambohimitombi , recorded on 16 February 2006 , 14:50 h, at Ankaratra, consists of a short, pulsed note ( Fig. 14 ), emitted in series at slow succession and somewhat irregular intervals. The calls were emitted from several shy animals at the border of a mountain stream, partly underwater, and identification of the calling specimen was therefore impossible. Notes exhibit slight amplitude modulation, with maximum call energy occurring either at first third of the note’s length or at the centre of the note, and the terminal pulse of the note always being of lowest energy. The initial pulse is sometimes separated from the second pulse by a slightly longer inter-pulse interval. Numerical parameters of 20 analysed calls are as follows: call duration (= note duration) 136– 218 ms (180.2 ± 18.7 ms); 9–14 pulses per note (10.9 ± 1.5); pulse duration 5–8 ms (6.3 ± 1.0 ms); pulse repetition rate within notes 56.1–69.3 pulses/s (62.3 ± 5.1); dominant frequency 925–1012 Hz (959 ± 30 Hz); prevalent bandwidth 500–3100 Hz; call repetition rate (= note repetition rate) in regular series ca 11–20 calls/ min. Tadpoles. —A tadpole of M. a. ambohimitombi was described under the name ‘ M. sp. aff. curtus “Ankaratra”’ by Schmidt et al. (2009) .

Diagnosis .— Mantidactylus ambohimitombi is a member of the M. curtus clade; it is here defined as containing three deep genetic lineages considered as subspecies, and is sister to the morphologically very distinct M. madecassus . See Table 4 for a list of diagnostic morphological characters. The following account only diagnoses the nominal subspecies M. a. ambohimitombi from other species in Brygoomantis ; see below for diagnoses and comparisons of the two other subspecies. The combination of relatively large body size of up to 51 mm at Ankaratra (up to 65 mm in the type series from Ambohimitombo forest), slightly granular skin without dorsolateral ridges in most specimens, strongly developed foot webbing with fully webbed fifth toe, small tympanum diameter with a maximum of 11% of SVL in males, distinguishes M. a. ambohimitombi from species of the other clades. Within the M. curtus clade, M. alutus , M. madecassus and M. pauliani have smaller body sizes and are distinguished by either a usually shorter snout ( M. madecassus , M. pauliani ), or advertisement calls emitted in regular series (in M. alutus , vs single notes) ( Table 4 ); M. curtus usually has a smoother skin and a somewhat shorter snout; M. bourgati is morphologically very similar but appears to occur only on the Andringitra Massif. 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. a. ambohimitombi in pairwise comparisons to all other Brygoomantis species is provided as Supplementary appendix.