Gephyromantis

Wollenberg, Katharina C., Glaw, Frank & Vences, Miguel, 2012, Revision of the little brown frogs in the Gephyromantis decaryi complex with description of a new species, Zootaxa 3421, pp. 32-60 : 54-55

Gephyromantis sp. 7

Remark. We follow Vieites et al. (2009) and Kaffenberger et al. (2012) who considered this candidate species as Gephyromantis sp. 7.

Identity and rationale for candidate species assignment. As discussed in the general results sections above, specimens collected in Manakara have the shortest note duration within the G. decaryi complex, and do not share haplotypes in 16S, COB, and RAG1 with the other species. However, we here refrain from describing this population and instead continue to consider it as candidate species until further evidence becomes available, based on the following arguments: (1) the amount of genetic differentiation of this lineage (1.5% 16S divergence to its sister lineage ( G. hintelmannae ) is very low; (2) it shows no convincing morphological or morphometric differences to G. hintelmannae ; and (3) different from G. decaryi , G. hintelmannae and G. verrucosus , it has been collected only at a single instance at a single site, and therefore too little information on its variation is available.

Material examined. ZSM 2489/2007 ( ZCMV 5421), ZSM 2490/2007 ( ZCMV 5422), ZSM 2491/2007 ( ZCMV 5424), ZSM 2492/2007 ( ZCMV 5485), all adult males, collected in the town Manakara, south-eastern Madagascar, 22°08'S, 48°01'E (precise coordinates not taken), ca. 20 m above sea level, by M. Vences, G. Safarek, E. Rajeriarison and T. Rajoafiarison on 22 February 2007.

Diagnosis. A member of the subgenus Gephyromantis in the genus Gephyromantis on the basis of (1) presence of intercalary elements between ultimate and penultimate phalanges of fingers and toes (verified by external examination), (2) small size (SVL below 35 mm), (3) slightly enlarged terminal discs of fingers, (4) presence of outer metatarsal tubercle, (5) absence of webbing on hands and presence of only rudimentary webbing on feet, (6) tight connection of tissue surrounding the two lateral metatarsalia, (7) presence of femoral glands in males, (8) presence of paired or bilobed blackish vocal sacs in males, (9) diurnal calling behavior not concentrated at water bodies.

Within the subgenus, distinguished from all other species by combination of (1) comparatively moderate size (male SVL 25–26 mm), (2) dorsum relatively smooth with few scattered distinct but relatively small tubercles and without dorsolateral ridges, (3) upper lip with light gray or white color that can be interrupted by 2–4 relatively small and indistinct dark markings, (4) lower lip ventrally without a distinct alternating series of brown and yellowish markings; (5) dorsal color light brown without contrasted pattern, (6) hindlimbs not particularly long, not reaching beyond snout tip, (7) calls consisting of a rather long series of>30 very short notes of less than 50 ms duration and with a low note repetition rate of 3.6–4.6/s.

Assigned to the group of species here informally defined as the Gephyromantis decaryi complex based on its molecular phylogenetic relationships (see above) and its calls which are long series of notes with a low note repetition rate. Distinguished from G. d e c a r y i by lacking inner and outer dorsolateral ridges (vs. distinct and usually not interrupted, Fig. 6 ), by the shorter limbs (tibiotarsal articulation at most reaching snout tip vs. reaching beyond snout tip), and by a shorter note duration (25–41 vs. 65–120 ms; see Table 2 ) in advertisement calls. Distinguished from G. verrucosus by the more distinct femoral glands in males (versus small and indistinct), by the less granular dorsum (few scattered tubercles versus regular large tubercles, Fig. 6 ), by the less contrasted dorsal coloration, and by a much shorter note duration (25–41 vs. 123–157 ms; see Table 2 ) in advertisement calls. Distinguished from G. hintelmannae by a lower number of notes (<80 versus>100) in advertisement calls, and by a shorter note duration (25–41 vs. 81–103 ms; see Table 2 ) in advertisement calls.

Description of reference specimen. ZSM 2492/2007, adult male ( Fig. 11 ). Specimen in excellent state of preservation, on the right femur a tissue sample was taken for DNA analyses. SVL 25.0 mm. For measurements see Table 1. Body slender, ratio of head length to head width HL/HW = 1.15, head slightly wider than body, snout pointed in dorsal view, rounded in lateral view; nostrils directed posterolaterally, slightly protuberant, canthus rostralis moderately distinct, rounded; loreal region concave; tympanum distinct, rounded, ratio of tympanum diameter to eye diameter TD/ED = 0.55; supratympanic fold distinct but weakly developed; tongue ovoid, posteriorly bifid; maxillary teeth present; vomerine teeth absent; choanae rounded. Arms slender, distinct single subarticular tubercles; inner and outer metacarpal tubercles recognizable; fingers without webbing; relative length of fingers 1<2<4<3, fourth finger longer than second finger; first finger almost as long as second finger finger disks distinctly enlarged; nuptial pads absent. Hindlimbs slender; tibiotarsal articulation reaches the snout tip when the hindlimb is adpressed along the body; lateral metatarsalia strongly connected; inner and outer metatarsal tubercles distinct; traces of webbing between toes; relative length of toes 1<2<5<3<4; fifth toe shorter than third toe. Skin on the dorsal surface smooth, with a discontinuous, very weakly developed and interrupted dorsolateral ridges in the middle section of the dorsum. Very weak, interrupted ridges on the lateral sides with the appearance of tubercles. Ventral skin smooth on throat, chest and limbs, granular on central and posterior belly. The subgular vocal sac is laterally black, probably indicating a paired or bilobed shape when inflated, femoral glands are well developed with a smooth surface, indistinct in external view.

After almost three years in preservative, dark brown with a lighter snout region and few dark markings on dorsum. Color on snout distinctly lighter, with a sharp transversal transition between light anterior and dark posterior color between the eyes ( Fig. 4 g). On the flanks, the dorsal color gradually fades into the light ventral coloration. The tympanic area is light brown; dark brown black stripe runs along the supratympanic fold; weak white mottling along the upper lip; dark markings around the forelimb insertion. Well-defined dark brown crossbands are present on the legs. Ventrally, the color is dirty white, with some brown mottling extending from the dorsal side to the ventral side of shanks and thighs. A white median band (broken twice), bordered by tan coloration and some additional white blotches, runs along the throat and chest, which also has some additional white markings on tan ground. The lower lip shows ventrally a distinct alternating brown-white pattern (three and four white spots on each side). The anterior belly has some white pigment on tan background.

Variation. For differences in measurements see Table 1. ZSM 490/2007 (ZCMV 5422) has a much lighter dorsum, with dark brown spots along the dorsolateral ridge lines. Femoral gland patches are much larger in ZSM 2489/2007 (ZCMV 5421) and ZSM 2491/2007 (ZCMV 5424) than in the reference specimen, and in ZSM 2490/ 2007 (ZCMV 5422) these are equally developed as in the reference specimen. In life ( Fig. 4 g–h) specimens were dorsally light brown with indistinct yellowish brown markings. The belly was centrally silvery white with yellowish sides posteriorly, in the ventral parts of the inguinal region. Femoral glands dark yellow. Iris light brown, with a small dark brown spot centrally in the lower part, and some dark color at the lateral edges.

Natural history. Specimens were observed in a pineapple plantation with relatively large shadow trees within a largely urban area with huts, gardens, ricefields, and next to a road, near the center of the town of Manakara. We discovered this population by coincidence, noting the loud calls which were emitted in the late afternoon during a cyclone period with very heavy rains. We collected specimens during a short interval with only weak rain, but specimens were also calling during rainfall. They were highly motivated, sometimes calling from largely exposed perches between 10–100 cm above the ground, and continued calling while the observers approached. Calling specimens were not close to any water body, suggesting a possible nidicolous reproduction as in other species of the subgenus Gephyromantis .

Advertisement calls. Three recorded calls consisted of 50, 65 and 67 notes, respectively. Note repetition rate was 3.6/s. Notes were distinctly shorter than those of all other species of the G. d e c a r y i complex studied here (see Table 2 for temporal measurements). Only 2–4 intensity maxima (pulses) could be recognized per note. Fundamental frequency was 2000–2200 Hz, dominant frequency was 3800–5000 Hz. A further weak frequency component was recognizable between 6000–7000 Hz.

Distribution. Only known from one site in the coastal town of Manakara. Since the species was found in secondary vegetation it is likely that it also is common in other plantations and in remains of secondary forest around Manakara.

Figures

FIGURE 4. Comparative dorsolateral and ventral views of males of the four species respectively candidate species in the Gephyromantis decaryi complex. (a, b) Gephyromantis decaryi from Ranomafana, specimen photographed in 2007 and preserved in the UADBA collection; (c, d) Gephyromantis verrucosus from Manombo, specimen ZSM 2508 / 2007 (field number ZCMV 5495); (e, f) Gephyromantis hintelmannae from Ambohitsara, holotype specimen ZSM 2500 / 2007 (field number ZCMV 5230); (g, h) Gephyromantis sp. 7, specimen preserved in UADBA (field number ZCMV 5484).

FIGURE 6. Photographs of dorsal skin structure in preserved specimens of (a) Gephyromantis decaryi (ZSM 2497 / 2007; field number ZCMV 5223), (b) G. verrucosus (ZSM 2462 / 2007; ZCMV 5459), (c) G. hintelmannae (holotype ZSM 2500 / 2007; ZCMV 5230), and (d) G. sp. 7 (ZSM 2492 / 2007; ZCMV 5485). Note continuous dorsolateral ridges in G. decaryi, discontinuous ridges and elongated tubercles in G. verrucosus, and relatively smooth skin with weakly expressed ridges in G. hintelmannae and G. sp. 7. Scale bars represent 1 mm.

FIGURE 11. Preserved specimens of the species and candidate species in the Gephyromantis decaryi complex; left—dorsal, right—ventral view. A— G. d e c a r y i (ZSM 2597 / 2007; field number ZCMV 5223); B— G. hintelmannae (holotype 2500 / 2007; ZCMV 5230); C— G. sp. 7 (ZSM 2492 / 2007; ZCMV 5485); D— G. verrucosus (ZSM 2462 / 2007; ZCMV 5495). Not to scale (see Table 1 for precise measurements of the specimens).