Guibemantis diphonus, Vences, Miguel, Jovanovic, Olga, Safarek, Goran, Glaw, Frank & Köhler, Jörn, 2015

Vences, Miguel, Jovanovic, Olga, Safarek, Goran, Glaw, Frank & Köhler, Jörn, 2015, A new arboreal frog of the genus Guibemantis from the southeast of Madagascar (Anura: Mantellidae), Zootaxa 4059 (3), pp. 569-580 : 570-577

Guibemantis diphonus sp. nov.

Holotype. ZSM 2665/2007 (field number ZCMV 5496), adult male ( Fig. 1 A −D), collected in Manombo Special Reserve (coordinates not taken, but about -23.01 / 47.73), Fianarantsoa Province, southeastern Madagascar, on 23 February 2007, by M. Vences, G. Safarek, E. Rajeriarison and T. Rajoafiarison.

Paratype. ZSM 2664/2007 (field number ZCMV 5416), adult male ( Fig. 1 E −F), same data as holotype.

Remarks. This species has been referred to as Guibemantis sp. 20 by Vieites et al. (2009) and Wollenberg et al. (2011), as Guibemantis sp. aff. timidus by Glaw & Vences (2007: 446) and as Guibemantis sp. Ca20 by Perl et al. (2014). DNA sequence data for the holotype specimen ZSM 2665/2007 are available for the mitochondrial 16S rRNA gene from Vieites et al. (2009) under GenBank accession number FJ559212 , and for the mitochondrial cytochrome b and cytochrome oxidase subunit 1 genes from Wollenberg et al. (2011) under accession numbers JN133051 and JN133275 .

Diagnosis. The species is allocated to the subgenus Guibemantis in the genus Guibemantis based on the structure of femoral glands in males (of type 1 sensu Glaw et al. 2000; Vences et al. 2007), arboreal habits, molecular phylogeny ( Vieites et al. 2009; Wollenberg et al. 2011; Perl et al. 2014), white single subgular vocal sac, smooth dorsal skin without dorsolateral ridges, enlarged terminal disks of fingers and toes and complete separation of lateral metatarsalia. The new species is distinguished from all species of the subgenus Pandanusicola in the genus Guibemantis by larger body size (male SVL 34−36 mm vs. <34 mm in males of Pandanusicola , and <31 mm in females of Pandanusicola except G. flavobrunneus ; Glaw & Vences 2007; Lehtinen et al. 2011, 2012; Vences et al. 2013), numerous details of colouration, natural history, bioacoustics (where advertisement calls are known), and mitochondrial differentiation.

Within the subgenus Guibemantis (comparative values from Vences & Glaw 2005 and Table 1 herein) the new species is distinguished from G. kathrinae and G. tornieri by its distinctly smaller body size (adult male SVL 34−36 mm vs. 57−59 mm in G. kathrinae , 42−58 mm in G. tornieri ). Its body size also seems to be smaller than in most specimens of G. depressiceps , despite overlap of values: male SVL is 32−45 mm in G. depressiceps , with many specimens reaching sizes> 40 mm. Moreover, rudimentary webbing is almost absent in G. diphonus whereas it is rather distinct in G. tornieri and often well visible in G. depressiceps . In addition, the metacarpal tubercle of G. diphonus is larger and more distinct compared to many though not all specimens of G. depressiceps and G. tornieri .

In a direct comparison with its sister species, G. timidus , the new species G. diphonus sp. nov. differs in the following morphological characters: (1) G. diphonus has a smaller average body size of males (average SVL 35 mm vs. 41 mm) despite overlapping values (34−36 mm vs. 32−45 mm) (n = 2 vs. n = 10; G. timidus measurements from Vences & Glaw 2005 and Table 1 herein). (2) G. diphonus has a very distinct metacarpal tubercle. Despite variation in this character, this tubercle is typically more flat and less distinct in G. timidus ( Fig. 2 ). (3) Hand length in G. timidus is typically shorter than in other species of the subgenus Guibemantis (HAL/SVL ratio <0.32, Vences & Glaw 2005), and this is also true for the two south-eastern G. timidus specimens from Beronono measured herein (HAL/SVL 0.28−0.29; Table 1 ). In the holotype of G. diphonus relative hand length is 0.32 and thus longer than the range known from G. timidus , although in the paratype the value is within the G. timidus range (0.29). Despite the low sample size it might be concluded that relative hand length values at least in some specimens of G. diphonus are higher than in G. timidus . (4) G. diphonus has in general a more contrasted and vivid colouration than G. timidus . Patterns like the dark dorsal crossbands on shanks (seen in the two G. diphonus specimens), the reddish colour on forelimbs, dark dorsal patches, broad light dorsal stripe or dark colour on flanks (seen each in only one of the two G. diphonus specimens) were never present in any of the relatively large number of G. timidus that we observed as preserved vouchers and in the wild.

Molecular phylogenetic data ( Vieites et al. 2009; Wollenberg et al. 2011; Perl et al. 2014) place the new species with moderate to high support as sister species of G. timidus . Its pairwise genetic divergence to G. timidus in the analysed 16S rRNA gene fragment is 4.4% ( Vieites et al. 2009), and differentiation to all other nominal species of Guibemantis is> 5%. This molecular divergence was also confirmed in comparison to a G. timidus sample from a syntopic specimen from Manombo (GenBank accession number HQ456658 ).

Furthermore, the species differs from all species in the subgenus by its advertisement call consisting of two distinctly different note types (see call description and comparisons below).

Description of the holotype. Adult male in excellent state of preservation. A small piece of muscle tissue from right thigh removed for molecular analysis. For measurements see Table 1 . Body relatively slender; head longer than wide, wider than body; snout slightly pointed in dorsal and relatively truncate in lateral view; nostrils directed laterally, slightly protuberant; canthus rostralis distinct, straight; loreal region concave; tympanum distinct, relatively small, its diameter 64% of eye diameter; distinct supratympanic fold; tongue ovoid, distinctly bifid posteriorly; vomerine teeth as one distinct oblong group posterolateral of each choana; choanae medium-sized, rounded. Forelimbs slender; subarticular tubercles distinct and single; central metacarpal tubercle large and oval, outer metacarpal tubercle smaller and elongated; a small prepollex (which could also be considered as an inner metacarpal tubercle) at the base of the first finger recognizable. Fingers without webbing; relative finger length 1<2<4<3; finger disks distinctly enlarged; nuptial pads absent. Limbs slender; when adpressed along body, the tibiotarsal articulation reaches beyond the eye; lateral metatarsalia separated; inner metatarsal tubercle distinct, larger than outer metatarsal tubercle; webbing formula of the foot 1(1), 2i (1.5), 2e(0.5), 3i (2), 3e(1), 4i (2), 4e(2), 5(1) (because only one subarticular tubercle is recognizable on the second toe, the relative extension of web on this toe can only be estimated); webbing according to the formula of Savage & Heyer (1997) I 2 – 2 + II 1 + – 3 III 2 – 3 IV 3 – 2 V. Relative toe length 1<2<3=5<4. Skin on the dorsum smooth; ventral skin smooth on throat and chest, slightly granular on belly. Femoral glands indistinct from external view, but of type 1 from internal view as defined by Glaw et al. (2000).

In preservative, dorsal ground colour uniformly brown, with a broad cream middorsal stripe of varying width (1−3 mm) and with irregular edges, running from snout tip to vent. Another transversal cream stripe of ca. 2 mm width between the anterior edges of the eyes. Tympanum brown. Whitish colour below the tympanun fading into grey towards the eye. Flanks brown marked with few greyish spots in the inguinal region. Upper arm and proximal part of the lower arm largely cream with few dark brown spots. Hands and fingers brown with dark brown spots. Hindlimbs brown with 3−4 dark brown crossbands. Ventral surfaces fading from bright white on the throat and cream white on the chest to light brown with some whitish marbling on the limbs. In general, colouration in life ( Fig. 1 ) is similar to that in preservative, but the yellow patches in the inguinal region and the reddish brown areas on the forelimbs have faded to grey and cream respectively.

Morphological variation. Morphometric measurements of the holotype and the paratype are provided in Table 1 . The paratype resembles the holotype in morphology, but is slightly larger, has relative shorter hindlimbs (tibiotarsal articulation reaches the eye versus beyond the eye), slightly more webbing between the toes with webbing formula 1(1), 2i (1.5), 2e(0.5), 3i (2), 3e(0.5), 4i (2), 4e(2), 5(1), a slightly smaller tympanum (56% of eye diameter), and toe 3 slightly shorter than toe 5 (relative toe length 1<2<3<5<4). It moreover differs in colouration: Head and dorsum are light brown with some faint greenish tint partly recognizable. Few poorly distinct brown patches in the vertebral region and between the eyes, and a small dark spot in the middle of the snout. A light middorsal stripe or line and a stripe between the eyes are lacking. Flanks are darker brown with numerous white spots. Dorsal surfaces of arms and hindlimbs similar to the holotype, but slighty lighter and with more contrasting crossbands. Ventral colour similar to the holotype, but slightly lighter on the belly.

Advertisement call. Vocalizations of two individuals of Guibemantis diphonus emitted at a regular basis were heard at Manombo, where also G. timidus was calling at the same time. Calls were obtained from one of the type specimens (recording temperature not taken but estimated ca. 25°C) and are composed of two distinctly different note types ( Fig. 3 ). The first note type is rather long (note duration 740−998 ms) composed of multiple pulses (29−44 pulses/note) emitted with relatively low energy, followed by a single short note type (note duration 10−24 ms) with comparatively much higher energy containing a single pulse only. The two different note types are separated by an interval of 155−181 ms. The duration of the call (here defined from the beginning of the first note type to the end of the second note type) is 1055 ± 98 ms (941−1177 ms). Within the first note type, pulses are somewhat irregularly arranged in 12−17 groups containing either two or three pulses, with each pulse group separated by slightly larger intervals from the following pulse group, compared to inter-pulse intervals within a pulse group. Pulse repetition rate within the first note type ranges from 35.5−50.1 pulses per second. Frequency ranges between 1100−3500 Hz, with a dominant frequency peak at approximately 2320 Hz. For detailed numerical parameters see Table 2. Calls of the second specimen were very similar according to field notes but recordings are of poor quality and cannot be analyzed in detail.

Species and Note duration [ms] Pulses/ Pulses/second Inter-note Frequency range Dominant frequency Recording Locality note within call interval [ms] [Hz] peak [Hz] temperature [°C] G. diphonus sp. nov. Note type Note type 1: Note type 1: 165 ± 12 1100−3500 2320 ± 102 ca. 25 Manombo (n = 6) 1: 843 ± 85 33.8 ± 5.3 41.6 ± 7.6 (155−181) (2174−2444)

(740−998) (29−44) (35.5−50.1)

Note type 2:

10−24

G. timidus 125 ± 17 3.3 ± 0.8 48.1 ± 10.9 NA 800−2800 1599 ± 181 ca. 25 Manombo (n = 7) (100−147) (2−4) (36.1−58.8) (1280−1719) G. timidus 106 ± 23 2.1 ± 0.4 27.0 ± 6.0 NA 1000−2500 1768 ± 52 -- Nosy Boraha (n = 7) (65−120) (2−3) (22.7−35.7) (1713−1821) G. tornieri 346 ± 41 4.8 ± 0.4 12.3 ± 0.5 NA 800−2100 1127 ± 103 ca. 25 Manombo (n = 5) (277−384) (4−5) (12.3−13.4) (973−1195) G. depressiceps 113 ± 25 3.7 ± 0.8 30.5 ± 1.9 NA 1000−3200 1808 ± 23 19.5 Ranomafana (n = 6) (90−160) (3−5) (28.6−33.0) (1775−1841) G. depressiceps 139 ± 26 4.2 ± 0.8 31.3 ± 1.8 NA 1200−3100 1977 ± 143 19−20 Andasibe (n = 6) (91−161) (3−5) (29.9−33.3) (1820−2100) G. kathrinae 329 ± 44 6.2 ± 0.9 19.0 ± 1.6 NA 850−1700 (1250−1550) 21 An’Ala (n = 4) (268−372) (5−7) (17.3−21.1)

Among the species in the subgenus Guibemantis , the advertisement call of G. diphonus is unique in being composed of two distinctly different note types, whereas all other species as far as known exhibit a single pulsed note type only (see Fig. 4 ). Comparing the first pulsed note type of G. diphonus with pulsed notes of other related Guibemantis species, it differs from all of these by a much longer note duration (740−998 ms versus maximum 384 ms or far less in other species) and a far higher number of pulses per note (29−44 versus 7 or less pulses/note), at a somehow comparable pulse repetition rate. Furthermore, in G. diphonus the two note types do not only differ in temporal characters, but also with respect to their relative amplitude, with the second note type being emitted with distinctly higher energy compared to the first note of the call. Given these very distinct advertisement call characters, G. diphonus can be readily identified by its vocalization alone.

Etymology. The specific epithet is derived from the Greek root word “phon” meaning “sound” and the prefix “di-” meaning “two”. In phonetics, a diphone is an adjacent pair of phones. The advertisement call of Guibemantis diphonus is characterized by the distinct combination of two note types. The specific epithet is used as latinized adjective.

Natural history. The two males of the new species were collected at night on 23 February 2007 along a very small moving shallow stream of ca. 2−3 m in width and 50 cm in depth within a disturbed area of the low-altitude rainforest of Manombo Special Reserve. Specimens were sitting on perches about 50 cm above the ground in the low vegetation, directly next to the stream. Along the same stream, a dense chorus of G. timidus was present, together with a few individuals of G. tornieri calling. The site was close to a swamp area with numerous G. liber .

Distribution. The species is only known from Manombo Special Reserve in southeastern Madagascar.

Available earlier names. Rhacophorus mocquardii Boulenger, 1896 , and Mantidactylus acuticeps Ahl, 1929 , both considered to be junior synonyms of Guibemantis depressiceps , could potentially be available as earlier names for G. diphonus . However, the new species can be distinguished from the holotype of Rhacophorus mocquardii (BMNH 1947.2.8.62) by the almost complete lack of webbing between fingers 1 and 2 (see Fig. 2 ), and from the holotype of Mantidactylus acuticeps (ZMB 30496) by the complete lack of dark ventral spots and dark colour on limbs (colour patterns typical for specimens assigned to G. depressiceps ). Furthermore, as documented in Figure 2 , the metacarpal tubercle in these two type specimens, and in the lectotype of depressiceps , are more flat and less distinct compared to G. diphonus . Although this is not a fully diagnostic character, we have observed in numerous more freshly preserved specimens of G. depressiceps the more flat condition of this tubercle (e.g., ZSM 668/2001, 703/2003, 329/2010, 330/2010; see also Fig. 2 ), similar to what is seen in the type of R. mocquardii .

Figures

FIGURE 1. Guibemantis diphonus sp. nov.: A − B, male holotype ZSM 2665 / 2007 from Manombo in life in dorsolateral and ventral view; C − D, male holotype ZSM 2665 / 2007 in preservative (photographed in May 2015); E − F, male paratype ZSM 2664 / 2007 shortly after preservation (photographed on 24 February 2007). Scale bars = 5 mm.

FIGURE 2. Views of palmar surfaces of left hands of species in the subgenus Guibemantis (not to scale). Note the very distinct metacarpal tubercle of G. diphonus which is smaller or more flattened in all other figured specimens (especially in the types of earlier names, e. g. Rhacophorus mocquardii from the east coast locality Sahambendrana). Moreover, there are differences in webbing between fingers: although rudimentary in all species, it is almost absent in G. diphonus, but rather distinct in G. tornieri and sometimes visible in G. depressiceps, and also recognizable in the mocquardii holotype.

FIGURE 3. Audiospectrogram and corresponding oscillogram of the advertisement call of Guibemantis diphonus sp. nov., recorded at Manombo Special Reserve on 23 February 2007 (temperature not taken but estimated ca. 25 ° C).

FIGURE 4. Comparative oscillograms (2000 ms sections each) of advertisement calls of species in the subgenus Guibemantis. For detailed call parameters see Table 2. Oscillogram of G. kathrinae taken from Glaw et al. (2000) showing a series of four calls according to the definition followed herein.

Tables

TABLE 1. Morphometric measurements of Guibemantis diphonus and comparative specimens of G. timidus and G. tornieri, all in mm. Abbreviations as in Materials and Methods except for: HT, holotype; PT, paratype; M, male; RHL, relative hindlimb length given as the point reached by tibiotarsal articulation when hindlimb is adpressed along body (1, posterior eye corner; 2, eye center; 3, anterior eye corner; 4, between eye and nostril).

Voucher	Status	Sex	SVL	HW	HL	TD	ED	END	NSD	NND	FORL	HAL	HIL	FOL	FOTL	TIBL	RHL
G. diphonus (Manombo)
ZSM 2665/2007 (ZCMV 5496) ZSM 2664/2007 (ZCMV 5416) G. tornieri (Manombo)	HT PT	M M	33.5 36.1	11.9 12.0	14.2 14.1	2.8 2.5	4.4 4.4	4.0 3.9	1.9 1.9	3.2 3.2	22.1 22.3	10.8 10.4	55.8 55.3	16.7 16.4	25.1 26.0	16.5 17.4	4 3
ZSM 2668/2007 (ZCMV 5478) G. timidus (Beronono)	--	M	58.4	18.6	20.9	3.6	6.9	5.9	2.8	5.4	33.4	16.3	85.6	26.5	39.4	25.0	1
ZSM 2666/2007 (ZCMV 5419) ZSM 2667/2007 (ZCMV 5427)	-- --	M M	43.4 37.0	15.2 13.1	16.7 15.0	2.7 2.7	4.5 4.8	4.8 4.3	2.3 2.0	3.9 3.5	26.5 23.7	12.3 10.8	61.8 55.8	19.5 17.3	28.5 25.9	18.6 17.4	1 2