Guibemantis rianasoa, Gabriel & Rothe & Köhler & Rakotomanga & Edmonds & Galán & Glaw & Lehtinen & Rakotoarison & Vences, 2024

Gabriel, Hugh, Rothe, Laila-Denise, Köhler, Jörn, Rakotomanga, Sandratra, Edmonds, Devin, Galán, Pedro, Glaw, Frank, Lehtinen, Richard M., Rakotoarison, Andolalao & Vences, Miguel, 2024, Unexpected diversity and co-occurrence of phytotelmic frogs (Guibemantis) around Andasibe, one of the most intensively surveyed amphibian hotspots of Madagascar, and descriptions of three new species, Zootaxa 5397 (4), pp. 451-485 : 465-471

Guibemantis rianasoa sp. nov.

( Figs 6 , 7 , 12)

Remark. This species has not been reported from Andasibe in previous publications, but based on a specimen from Fierenana, it was named Guibemantis sp. aff. punctatus “Fierenana” in Glaw & Vences (2007), G. sp. 14 in Vieites et al. (2009) and G. sp. Ca 14 in Perl et al. (2014).

Holotype. ZSM 149/2022 (field number ZCMV 13705 ), adult male, collected by M. Vences, S. Rakotomanga, S. Rasamison, and P. Galán on 17–18 November 2022 at Andasibe , VOI (VOIMMA) forest, central eastern Madagascar, approximate coordinates -18.9277, 48.4186, ca. 950 m above sea level.

Paratypes. Five specimens: ZSM 148/2022 ( ZCMV 13704 ), adult male, same collection data as holotype; ZSM 150/2022 ( ZCMV 15636 ), ZSM 151/2022 ( ZCMV 15637 ), UADBA-ZCMV 15633, and UADBA-ZCMV 15634 , four adults (probably females) collected by A. Rakotoarison on 14–15 June 2022 in the Andasibe area .

Definition. Assigned to the subgenus Pandanusicola in the genus Guibemantis based on its small body size, phytotelm-dwelling habitats (in Pandanus plants), near-absent webbing between toes, connected lateral metatarsalia, presence of both inner and outer metatarsal tubercles, intercalary elements between ultimate and penultimate phalanges of fingers and toes (verified by external examination), presence of femoral glands in males (absent in females) consisting of well-delimited (though poorly recognizable) femoral macroglands with discrete enlarged gland granules and without externally visible central depression, and presence of whitish color laterally on throat (marking the vocal sac) in males (absence in females), and molecular phylogenetic affinities.

The new species is characterized by the unique combination of: (1) small size, with adult male SVL up to 20 mm in genotyped individuals (possibly up to an exceptional 27 mm according to field data from non-genotyped individuals), (2) dull greenish (not bright translucent green) dorsally, without purplish spots, (3) distinct brown rostral stripe, (4) presence of a few rather distinctly contrasted white-silvery flecks on the posterior flanks, (5) often copper-golden color above the eyes, (6) absence of webbing on hand and only traces of web at foot, (6) vomerine teeth present, (7) femoral (macro)glands of males small and poorly marked.

Although some individuals with atypical coloration may be difficult to distinguish from subadults of other Pandanusicola species, G. rianasoa is overall rather easily diagnosable, and it does not appear to have clear phylogenetic affinities to other species. The species is also characterized by numerous diagnostic nucleotide positions in the mitochondrial 16S rRNA gene: MolD identified a robust diagnostic nucleotide combination of an 'A' in the site 1203, 'T' in the site 1307, 'A' in the site 1329 (positions relative to the full 16S rRNA gene of Mantella madagascariensis ).

Diagnosis. Distinction from G. fotsitenda , G. liber , G. razandry , G. razoky and G. tasifotsy : male femoral gland consisting of a well-delimited field of discrete enlarged single gland granules (vs. a diffuse field of small granules covering most of the ventral shank), occurrence limited to Pandanus leaf axils (vs. calling and breeding in open swamps), and low-intensity calls emitted from Pandanus vs. loud calls emitted from exposed perches above swamps.

Distinction from G. albolineatus : greenish dorsal color (vs. almost uniformly chocolate-brown), presence of silvery white dots on flanks (vs. absence), and absence of contrasted and well-delimited light dorsolateral bands (vs. presence).

Distinction from G. albomaculatus : smaller body size (male SVL ≤ 20 mm vs.> 20 mm in the majority of specimens), absence of fine white dotting on body (vs. presence especially on hindlimbs and sometimes on dorsum), presence of silvery white dots on flanks (vs. absence), and small and inconspicuously colored femoral glands (vs. larger and with contrasting yellowish color).

Distinction from G. annulatus : smaller body size (male SVL ≤ 20 mm vs.> 20 mm), olive greenish dorsal color (vs. light brownish), absence of small dark dots dorsally (vs. presence), presence of silvery white dots on flanks (vs. absence), and absent or poorly contrasted light ring proximal to finger and toe discs (vs. distinct and contrasted).

Distinction from G. bicalcaratus : smaller body size (male SVL ≤ 20 mm vs.> 20 mm), presence of a black vertical line in upper part of iris (vs. absence), olive greenish dorsal color (vs. light brownish), and presence of silvery white dots on flanks (vs. absence).

Distinction from G. flavobrunneus : much smaller body size (male SVL ≤ 20 mm vs. ≥ 30 mm), presence of silvery white dots on flanks (vs. absence), and an olive greenish dorsal color (vs. brown with contrasted light brown pattern).

Distinction from G. methueni : smaller body size (male SVL ≤ 20 mm vs.> 20 mm), olive greenish dorsal color (vs. light brownish), presence of silvery white dots on flanks (vs. absence), and males with white color only laterally on throat (vs. white color covering most of throat).

Distinction from G. milingilingy : smaller body size (male SVL ≤ 20 mm vs.> 20 mm), presence of silvery white dots on flanks (vs. absence), and small and inconspicuously colored femoral glands (vs. larger and with contrasting yellowish color).

Distinction from G. pulcher and G. pulcherrimus : smaller body size (male SVL ≤ 20 mm vs.> 20 mm in almost all specimens), non-translucent greenish dorsal color (vs. translucent green), absence of purple-reddish dots and markings on the dorsum (vs. presence), and small inconspicuously colored femoral glands (vs. larger and with contrasting yellowish color).

Distinction from G. punctatus : smaller body size (male SVL ≤ 20 mm vs.> 20 mm in the majority of specimens), olive greenish dorsal color (vs. light brownish), presence of silvery white dots on flanks (vs. absence), and absence of small dark dots dorsally (vs. presence).

Distinction from G. wattersoni : smaller body size (male SVL ≤ 20 mm vs.> 20 mm), olive greenish dorsal color (vs. light brownish), and presence of silvery white dots on flanks (vs. absence).

Distinction from G. woosteri : smaller body size (male SVL ≤ 20 mm vs.> 20 mm in almost all specimens), and presence of silvery white dots on flanks (vs. absence).

Description of the holotype. Adult male in good state of preservation ( Fig. 11 ). Tissue removed from ventral side of right thigh for DNA extraction. Head longer than wide and slightly wider than body; snout slightly pointed in dorsal and ventral views, more rounded in lateral view; canthus rostralis straight, loreal region flat; nostrils much nearer to tip of snout than to eye, tympanum distinct, 43% of horizontal eye diameter; supratympanic fold distinct, curved; vomerine odontophores small but distinct, located medially between eye and choanae on either side of head; maxillary teeth present; tongue ovoid, and distinctly bifid at its tip. Arms slender; relative finger length 1<2<4<3, second finger very slightly shorter than fourth finger; finger discs moderately enlarged and squared off at tips in a rounded ‘T’ shape, no webbing between fingers recognizable, subarticular tubercles distinct, unpaired. Hindlimbs moderately slender, foot length 82% of tibia length; lateral metatarsalia largely connected by muscular tissue; inner metatarsal tubercle oblong and recognizable, relatively small; outer metatarsal tubercle round, small and distinct; only traces of webbing recognizable between toes, especially toes 3, 4 and 5; relative length of toes 1<2<5<3<4, third toe slightly longer than fifth; toe discs moderately enlarged. Femoral glands visible but not very prominent. For morphometric measurements see Table 1 .

After ca. four months in preservative ( Fig. 11 ), dorsal surface is beige and mottled gray-green starting at the cloaca and stopping between the eyes. Beige dorsolateral bands present but not continuous, from sacral vertebrae bump up to the eyes. Rostral stripe is black and distinctly delimited, continues onto supratympanic fold before stopping at the forelimb insertion.Anterior flanks each marked with small and asymmetric white patches. Forelimbs and hindlimbs are beige with gray-green stripes, stripes are less distinct on hindlegs. Toe discs yellow. Ventral side beige, with faint black stippling visible on the underside of the hands, feet and thighs. In life, dorsal surface was greenish (of rather dull, only slightly translucent appearance, clearly less translucent than is typical for G. pulcher ) with faint mottling, transitioning to pale blueish on the hindlimbs and featuring asymmetric silver patches on the flanks ( Fig. 5 ).

Variation. Some frogs found in Andasibe have a blue tint towards the posterior parts of the body, and while the base green coloring remains relatively constant across specimens, a dark brown asymmetrical mottled secondary color is highly variable ( Figs 6–7 ). The dark brown secondary coloration can range from highly translucent to nearly black, usually concentrated on the flanks and towards the cloaca, but sometimes covering the entire specimen. Silver blotches on the flanks vary in size and shape but are usually distinct. Femoral glands of males are only weakly expressed and of the same color as the surrounding skin ventrally on thigh. Males only with a little amount of white color laterally on the throat (absent in females), and slightly smaller than females (SVL 18–27 mm in males, 19–26 mm in females, but only 12 out of 95 individuals> 23 mm; see section "Morphological differentiation" above). The only known specimen from Fierenana has a substantial divergence in its 16S sequence (3.0% to Andasibe samples) and also shows differences in coloration in life, with a somewhat vermiculated dark pattern evenly distributed not only on the dorsum but also on the flanks.

Etymology. The species epithet is derived from the Malagasy words riana (waterfall) and soa (beautiful), making reference to the greenish (somewhat greenish blue) color of the species with silvery blotches which remind colors of water reflecting forest vegetation. The name also makes reference to the “Rianasoa trail” in Mantadia National Park where we have observed the species. The name is used as a noun in apposition.

Natural history. Specimens were observed exclusively in Pandanus plants during the day. Of 253 Pandanus surveyed by HG in 2022, G. rianasoa was detected in 136 plants (53.7%) and co-occurred in syntopy with G. ambakoana in 76 plants (30.0%). Clutches observed in the Pandanus leaf axils could not be assigned to any of the various species occurring in syntopy as they were not genotyped. No further natural history or life history data are known.

Bioacoustics. Vocalizations were recorded in Analamazaotra Forest Station in the Andasibe area at 11:16 h during a period of light rain, at an air temperature of 19–21°C. The call ( Fig. 4A ) was recorded from ca. two meters distance close to a path in secondary humid forest. Notably, the calling individual was visually identified as Guibemantis rianasoa sp. nov. in the field and observed and videotaped, but the frog was not collected as a voucher and not sequenced. The following call description therefore cannot be attributed to this species with absolute certainty. Advertisement calls are rather soft and consist of a single very short pulsatile note, emitted at regular intervals within short call series containing two calls ( Fig. 4A ). Amplitude modulation is evident in each call, with maximum call energy present at the beginning of the call, slowly decreasing towards the call’s end. The initial call of each call series exhibits less call energy and has a lower dominant frequency when compared to the second calls of series. Numerical parameters of eight analyzed calls from two individuals are as follows: call duration (= note duration) 7–15 ms (10.8 ± 2.9 ms); inter-call intervals within call series 128–149 ms (138.5 ± 8.7 ms); number of calls per call series 2; duration of call series 151–171 ms (159.8 ± 8.4 ms); dominant frequency 3391–5071 Hz (4239 ± 784 Hz); prevalent bandwidth 2400–9400 Hz. Call repetition rate within call series was approximately 400 calls/minute.

Advertisement calls recorded on 19 November 2022 at Andasibe (air temperature not measured) are in general agreement with those described above, being rather soft and consisting of a single very short pulsatile note, emitted at regular intervals within short call series containing 2–3 calls. No vouchers were collected for these calls, but they were regularly heard from Pandanus plants in which only this species was found. Numerical parameters of 23 analyzed calls from at least two individuals are as follows: call duration (= note duration) 8–24 ms (13.4 ± 4.0 ms); inter-call intervals within call series 115–195 ms (132.3 ± 23.6 ms); number of calls per call series 2–3 (2.1 ± 0.4); duration of call series 147–232 ms (191.5 ± 58.4 ms); dominant frequency 3413–5092 Hz (4267 ± 545 Hz); prevalent bandwidth 2500–6500 Hz. Call repetition rate within call series was approximately 400 calls/minute.

Distribution. The species is so far only known from (1) the area around Andasibe and (2) Fierenana.At Andasibe, it has been found in the VOI forest, at Analamazaotra Forest Station, and within Analamazaotra-Mantadia National Park ( Figs 1–2 ).

Figures

FIGURE 1. Maximum Likelihood tree based on a DNA sequences of a fragment of the mitochondrial 16S rRNA gene (alignment length 545 bp) for 368 specimens of all species and candidate species of Guibemantis. See Koppetsch et al. (2023) for a discussion of the mitochondrial non-monophyly of species in the G. liber complex (G. fotsitenda, G. liber, G. razandry, G. razoky).

FIGURE 2. Map of Madagascar showing genetically verified locality records of the target species of Guibemantis studied herein (colors as in Fig. 1). The base map shows vegetation across Madagascar from the Madagascar Vegetation Mapping Project (Moat & Smith 2007; formerly available at www.vegmad.org). Vegetation is colored as follows: green, humid forest (rainforest); red, western dry deciduous forest; bluish, western subhumid forest; orange, south western dry spiny forest-thicket; yellow, tapia forest.

FIGURE 4. Audiospectrograms and oscillograms of advertisement calls of six species of Guibemantis of the subgenus Pandanusicola. A, call series (containing 3 calls) of Guibemantis rianasoa sp. nov., recorded on 19 November 2022 at Andasibe. Recording high-pass filtered at 2000 Hz. B, two calls of Guibemantis ambakoana sp. nov., recorded on 19 November 2022 at Andasibe. Recording high-pass filtered at 1500 Hz. C, three calls of Guibemantis vakoa sp. nov. recorded on 15 February 2004 at Besariaka. Recording band-pass filtered at 1500–9200 Hz. D, call series (containing 5 calls) of Guibemantis methueni recorded on 8 November 2011 at Andasibe. Recording high-pass filtered at 1000 Hz. E–F, calls of G. annulatus (from Lehtinen et al. 2011) and G. pulcher (from Vences et al. 2011).

FIGURE 5. Guibemantis rianasoa sp. nov. (sp. F / Ca14) in life. A–B. Male holotype ZSM ZSM 149/2022 (ZCMV 13705) from Andasibe VOI forest in dorsolateral and ventral view; C–D. Male paratype ZSM ZSM 148/2022 (ZCMV 13704) in ventral and dorsolateral view. E. Specimen from Fierenana (ZMA 19347; FGMV 2002.2418) in dorsolateral view.

FIGURE 6. Guibemantis rianasoa sp. nov. (sp. F / Ca14), color variation in life. All pictured specimens were photographed at Andasibe and were not collected or genotyped. Note presence of rather distinct silvery flank blotches in all specimens pictured in lateral view.

FIGURE 7. Guibemantis ambakoana sp. nov. (sp. A / Ca3) in life. A, F. Male holotype ZSM 152/2022 (ZCMV 13707) from Andasibe VOI forest; B, G. Female paratype ZSM 153/2022 (ZCMV 13717) also from Andasibe VOI forest; C, E. Male paratype ZSM 431/2016 (ZCMV 15001) from Andasibe (Analamazaotra forest); D. UADBA-ZCMV 15635 from Andasibe. Note the distinct femoral glands with orange tint present in male specimens.

FIGURE 11. Dorsal and ventral views of preserved holotypes of new Guibemantis species: A–B. Guibemantis rianasoa sp. nov. (sp. Ca14), male holotype ZSM 149/2022 (ZCMV 13705); C–D. Guibemantis ambakoana sp. nov. (sp. Ca3), male holotype ZSM 152/2022 (ZCMV 13707); E, F. Guibemantis vakoa sp. nov. (sp. Ca8), male holotype ZSM 389/2004 (ZCMV 931).

Tables

TABLE 1. Morphometric measurements (all in mm) of genotyped adults of species of Guibemantis targeted in this study. For abbreviations of measurements, see Materials and Methods; other abbreviations: HT, holotype; PT, paratype; M, male; F, female.

Catalogue number	Field number	Locality	Status	Sex	SVL	HW	HL	TD	ED	END	NSD	NND	FORL	HAL	HIL	FOTL	FOL	TIBL	FGL	FGW
G. rianasoa sp. nov. (F)
ZSM 149/2022	ZCMV 13705	Andasibe	HT	M	19.1	6.7	7.7	1.2	2.8	2.0	1.3	2.0	12.0	5.3	30.0	12.8	8.0	9.6	3.9	1.5
ZSM 148/2022	ZCMV 13704	Andasibe	PT	M	19.9	6.6	8.0	1.2	3.0	2.1	1.0	1.7	12.5	5.5	30.4	14.6	8.3	9.8	3.5	1.6
UADBA	ZCMV 15633	Andasibe	PT	F	20.1	6.7	8.8	1.3	2.6	2.1	1.8	2.1	13.1	5.9	31.5	13.8	9.0	10.2
UADBA	ZCMV 15634	Andasibe	PT	F	21.4	7.3	8.3	1.5	3.0	2.3	1.7	2.4	12.8	6.0	31.2	13.6	8.4	9.8
ZSM 150/2022	ZCMV 15636	Andasibe	PT	F	21.2	7.1	8.0	1.8	2.9	2.4	1.5	2.3	13.1	6.5	30.8	14.3	8.6	10.5
ZSM 151/2022	ZCMV 15637	Andasibe	PT	F	21.3	6.9	7.7	1.4	2.9	2.3	1.8	2.4	13.4	6.2	31.7	14.3	8.9	10.4
G. ambakoana sp. nov. (A)
ZSM 152/2022	ZCMV 13707	Andasibe	HT	M	23.7	7.7	9.3	1.8	3.6	2.4	1.3	2.1	14.3	7.1	37.4	16.9	10.8	12.1	5.1	1.9
ZSM 431/2016	ZCMV 15001	Andasibe	PT	M	22.6	7.6	9.1	1.8	2.9	2.5	1.2	1.8	14.0	6.0	35.0	15.5	9.6	11.4	5.7	2.0
ZSM 275/2016	FGZC 5296	S Moramanga	PT	M	24.0	8.1	9.5	2.0	3.8	2.2	1.7	2.5	15.6	7.3	36.7	17.4	11.0	12.3	5.4	1.9
ZSM 153/2022	ZCMV 13717	Andasibe	PT	F	23.7	8.5	9.6	1.8	3.5	2.3	1.4	2.0	15.5	7.3	39.0	16.9	10.6	12.9
ZSM 432/2016	ZCMV 15002	Andasibe	PT	F	26.0	9.0	11.1	2.2	3.6	2.8	1.6	2.3	16.3	7.8	48.5	17.4	10.8	12.8
UADBA	ZCMV 15635	Andasibe	PT	F	25.4	8.5	9.4	2.3	3.6	2.8	1.8	2.4	15.0	7.6	39.0	17.1	11.2	12.9
ZSM 156/2022	ZCMV 15638	Andasibe	PT	F	28.3	9.5	10.9	2.2	3.7	2.8	1.6	2.5	16.5	7.7	41.3	18.8	11.8	13.6
UADBA	ZCMV 15631	Andasibe	PT	F	22.8	7.4	9.3	2.0	3.5	2.4	1.5	2.6	14.3	7.0	35.0	16.6	10.1	11.8

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