Guibemantis ambakoana, 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 : 471-475

Guibemantis ambakoana sp. nov.

( Figs 8 , 9 , 12)

Remark. Individuals probably belonging to this species have been reported as Guibemantis bicalcaratus and G. albolineatus in Glaw & Vences (1994), G. cf. albolineatus in Lehtinen et al. (2007), G. sp. aff. albolineatus “Andasibe” in Glaw & Vences (2007), G. sp. 3 in Vieites et al. (2009) and G. sp. Ca 3 in Perl et al. (2014).

Holotype. ZSM 152/2022 ( ZCMV 13707 ), 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. Seven specimens. ZSM 153/2022 ( ZCMV 13717 ) and ZSM 154/2022 ( ZCMV 13718 ) , two adult females with same collection data as holotype; ZSM 156/2022 ( ZCMV 15638 ) , UADBA-ZCMV 15635 and UADBA-ZCMV 15631, three females collected by A. Rakotoarison, A.I.F. Hasiniaina and E. Desire on 14‒15 June 2022 in the Andasibe area ; ZSM 275/2016 ( FGZC 5296 ) , adult male, collected by F. Glaw, D. Pr ̂tzel, J. Forster, N. Raharinoro on 3 August 2016 south of Moramanga at geographical coordinates -19.06155, 48.23205, 962 m a.s.l.; ZSM 431/2016 ( ZCMV 15001 ) and ZSM 432/2016 ( ZCMV 15002 ) , one male and one female, collected by M. Vences on 10 November 2016 in the Analamazaotra Forest Station (“ Mitsinjo Forest ”, ca. -18.934, 48.410) .

Referred specimen. ZSM 155/2022 ( ZCMV 15632 ), one female of mitochondrial lineage E, collected by A. Rakotoarison, A.I.F. Hasiniaina and E. Desire on 14–15 June 2022 in the Andasibe area .

Definition. Assigned to the subgenus Pandanusicola in the genus Guibemantis based on its small to medium 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 well-delimited femoral macroglands consisting of discrete enlarged gland granules and without externally visible central depression, and 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 combination of the following characters: (1) small size with adult SVL up to 24 mm in males and up to 28 mm in females in genotyped individuals (up to 27 mm / 30 mm based on field measurements of non-genotyped individuals), (2) light brownish dorsal color, often without distinct darker markings or spots, (3) distinct brown rostral stripe, (4) no or only few, small whitish spots on (posterior) flanks, (5) often with incomplete or interrupted light brown, beige or yellowish dorsolateral stripes, (6) absence of webbing on hand and only traces of web at foot, (7) vomerine teeth present, (8) femoral (macro)glands of males distinct, very clearly recognizable and of contrasting reddish brown color in life, single gland granules well recognizable externally in life and preservative.

Although this combination of character states will allow a distinction from most other species of Guibemantis , especially the co-occurring G. flavobrunneus , G. pulcher , and G. rianasoa , it is more difficult to diagnose the species against other brownish-colored species such as G. albolineatus , G. bicalcaratus , G. methueni , or G. wattersoni . Furthermore, we here restrict the type series of this species to individuals belonging to mitochondrial lineage A, and their morphological diagnosis from lineage E is unclear. Thus, we define this species based on diagnostic nucleotide positions (typical for lineage A) in the mitochondrial 16S rRNA gene; MolD identified a robust diagnostic nucleotide combination of a 'T' in the site 1091, 'A' in the site 1108, 'A' in the site 1129, 'T' in the site 1134 (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 calls emitted from Pandanus vs. loud calls emitted from exposed perches above swamps.

Distinction from G. albolineatus : contrasted and well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. dorsolateral bands continuous).

Distinction from G. albomaculatus : absence of fine white dotting on body (vs. presence, especially on hindlimbs and sometimes on dorsum), males with white color only laterally on throat (vs. white color covering most of throat), and presence of well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. absent or poorly contrasted but continuous).

Distinction from G. annulatus : absence of a regular pattern of small dark dots dorsally (vs. presence), and absent or poorly contrasted light ring proximal to finger and toe discs (vs. distinct and contrasted).

Distinction from G. bicalcaratus : presence of well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. absence), and presence of a black vertical line in upper part of iris (vs. absence).

Distinction from G. flavobrunneus : smaller body size (male SVL 23–24 mm vs. ≥ 30 mm), and dorsum brown with well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. brown with contrasted light brown pattern).

Distinction from G. methueni : presence of well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. absent or poorly contrasted but continuous), femoral glands typically with contrasting yellow-orange color (vs. without contrasting color), and males with white color only laterally on throat (vs. white color covering most of throat).

Distinction from G. milingilingy : presence of well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. broader and continuous), and dorsal color brown typically without greenish shade (vs. yellowish green dorsolateral bands and dorsal markings).

Distinction from G. pulcher and G. pulcherrimus : brown dorsal color (vs. translucent green), and absence of purple-reddish dots and markings on the dorsum (vs. presence).

Distinction from G. punctatus : absence of a regular pattern of small dark dots dorsally (vs. presence), and presence of well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. absence).

Distinction from G. rianasoa : larger body size (male SVL 23–24 mm vs. ≤ 20 mm), brown dorsal color (vs. olive greenish), and large femoral glands with contrasting yellowish color in males (vs. small and inconspicuously colored).

Distinction from G. wattersoni : presence of well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. absent or poorly contrasted but continuous).

Distinction from G. woosteri : presence of well-delimited dorsolateral bands that are typically interrupted or present only on the central dorsum (vs. absent or poorly contrasted but continuous), and a brown dorsal color without greenish elements (vs. often a green shade, especially of dorsolateral bands).

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 wider than body; snout 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, 50% 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 slightly 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 89% 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; relative length of toes 1<2<5<3<4, third toe slightly shorter than fifth; toe discs moderately enlarged. Femoral glands distinct and prominent. For morphometric measurements see Table 1 .

After ca. four months in preservative ( Fig. 11 ), dorsal surface gray. Beige dorsolateral bands are faint and appear next to a distinct dark brown rostral stripe which stretches from the tip of the nose all the way along the anterior flanks, stopping at the hindleg insertion. A thin, vertical, straight line of maroon tint is visible in the center of the dorsal view. Tiny dots between the eyes and towards the snout. Forelimbs gray with dark brown discontinuous stripes, hindlegs gray, speckled with light brown. Ventral side beige, with faint black stippling on the underside of hands, feet, hindlegs, and around the mouth. In life ( Fig. 7 ), dorsal surface was golden brown, with a dark brown rostral stripe, and limbs were pale brown.

Variation. Variation is most obvious in the ground color of the frog, ranging from a pale, mottled beige to chocolate-brown ( Figs 8–9 ). Golden dorsolateral bands, usually present, ranging from continuous and clearly delimited, to patchy and small. Silver patches on the flanks are often present, but not always, and vary in size and shape, usually less contrasted than in G. rianasoa . Femoral glands are orange-brown, with distinct and clearly recognizable single gland granules inside the macrogland. Males only with a little amount of white color laterally on the throat (absent in females), and slightly smaller than females (field SVL measurements of non-genotyped individuals 20–27 mm in males, 20–30 mm in females; see section "Morphological differentiation" above).

Etymology. The species epithet is derived from the Malagasy word “vakoana”, used to refer to Pandanus screw pines; “am-bakoana” means “living in vakoana”, and refers to the species’ specialized habitat, living and reproducing in Pandanus leaf axils. The name is used as a noun in apposition.

Natural history. Specimens were observed exclusively in Pandanus plants. Calling males were observed in November 2022 sitting exposed on Pandanus leaves, during the day. Of 253 Pandanus surveyed by HG in 2022, G. ambakoana was detected in 103 plants (40.7%) and co-occurred in syntopy with G. rianasoa in 76 plants (30.0%). Nothing else is known.

Bioacoustics. Advertisement calls recorded on 16 November 2013 at Torotorofotsy (air temperature not recorded; call voucher not collected but agreeing in color pattern with this species) consist of a single short pulsatile note, emitted at long somewhat irregular intervals.Amplitude modulation is evident in each call, with maximum call energy present in the first quarter of the call, rapidly decreasing to a much lower level and further gradually fading towards the call’s end. Numerical parameters of 52 analysed calls are as follows: call duration (= note duration) 20–41 ms (31.3 ± 7.2 ms); inter-call intervals 1190–2520 ms (1826.7 ± 439.5 ms); dominant frequency 3156–3979 Hz (3629 ± 292 Hz); prevalent bandwidth 2200–5200 Hz. Call repetition rate was approximately between 23–48 calls/minute. Within the recordings, sometimes two calls were emitted in fast succession, with inter-call intervals ranging between 98–155 ms (122.7 ± 120.6 ms). It is unknown if these ‘double clicks’ are a regular part of the advertisement call, or possibly have another function (e.g. territorial).

Advertisement calls recorded on 19 November 2022 at Andasibe (air temperature not measured; one individual seen calling; Fig. 4B ) generally agree in character with those recorded at Torotorofotsy, except for being somewhat longer in duration. Numerical parameters of 43 analysed calls from at least two individuals are as follows: call duration (= note duration) 31–93 ms (63.4 ± 18.1 ms); inter-call intervals 780–2055 ms (1686.6 ± 381.4 ms); dominant frequency 3262–4124 Hz (3704 ± 278 Hz); prevalent bandwidth 2400–5000 Hz. Call repetition rate was approximately between 25–65 calls/minute.

Distribution. The species is known from (1) the type locality Andasibe, as well as two sites in the same general area of the Northern Central East of Madagascar, i.e., from forest fragments near (2) Moramanga, and (3) Anosibe An’Ala ( Figs 1–2 ). A specimen from Maharira in Ranomafana National Park is genetically highly divergent and is only tentatively assigned to this species (see Fig. 1 ).

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 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 8. Color variation in life in specimens assigned to Guibemantis ambakoana sp. nov. (sp. A / Ca3). All pictured specimens were photographed at Andasibe and were not collected or genotyped, and may therefore include both mitochondrial lineages A and E. Note absence of silvery flank blotches and distinct femoral glands with orange tint in the two male specimens pictured in ventral view.

FIGURE 9. Male individuals of Guibemantis vakoa sp. nov. from Besariaka (south of Moramanga), photographed in 2004. (A–B) Holotype ZSM 389/2004 (ZCMV 931). (C–D) Paratype ZSM 388/2004 (ZCMV 930) (assigned to species based on morphology only). Note the distinct orangish-brown femoral glands and only limited white throat pigmentation in comparison to syntopic specimens of G. methueni which have less distinctly pigmented glands and extended white throat color (Fig. 10).

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).