Rhacophorus bengkuluensis, Streicher, Jeffrey W., Hamidy, Amir, Harvey, Michael B., Anders, Ben, Shaney, Kyle J., Kurniawan, Nia & Smith, Eric N., 2014

Streicher, Jeffrey W., Hamidy, Amir, Harvey, Michael B., Anders, Ben, Shaney, Kyle J., Kurniawan, Nia & Smith, Eric N., 2014, Mitochondrial DNA reveals a new species of parachuting frog (Rhacophoridae: Rhacophorus) from Sumatra, Zootaxa 3878 (4), pp. 351-365 : 356-361

Rhacophorus bengkuluensis sp. nov.

( Figs. 3–6 )

Rhacophorus catamitus ( Harvey et al. 2002: 68, Fig. 11, in part, referred specimen)

Holotype. Museum Zoologicum Bogoriense Amphibian Collection, MZB.Amph.21194 (previously University of Texas at Arlington Amphibian Collection, UTA A- 54001; field no. MBH 5376), an adult female collected from southwest slope of Bukit Barisan range near Kepahiang, Kecamatan Taba Pananjung, Kabupaten Bengkulu Tengah, Provinsi Bengkulu, Sumatra, Indonesia (S 3.685556, E 102.538611, 600–650 m asl) on 30 May 1996 by Michael B. Harvey and Eric N. Smith (Harvey et al. 2002). The specimen was collected while inactive on a leaf, 2 m above the ground. The ambient temperature was 23°C at approximately 1930 h when the specimen was collected. Holotype GenBank 16S sequence KC701717 .

Paratypes (5). MZB.Amph.16308 (field number S40), an adult female collected near the type locality in Kecamatan Taba Pananjung, Kabupaten Bengkulu Tengah, Provinsi Bengkulu, Sumatra, Indonesia (ca. S 3.685556, E 102.538611, 600–650 m asl) on 19 July 2010 by A. Hamidy and Nurrohim. MZB.Amph.3449, an adult female collected near Dirgahayu Rimba, Kecamatan Napal Putih, Kabupaten Bengkulu Utara, Taman Nasional Bukit Barisan Selatan, Provinsi Bengkulu, Sumatra, Indonesia (ca. S 3.021965, E 101.926738, between 100–500 m asl) in July 1997 by Uni Eropa. MZB.Amph.3482, an adult female collected near Rata Agung, Kecamatan Lemong, Kabupaten Lampung Barat, Bukit Barisan Selatan National Park, Provinsi Lampung, Sumatra, Indonesia (ca. S 4.866696, E 103.704993, between 500–750 m asl) on 28 March 1998 by Andiek F. MZB.Amph.14628, an adult male collected from Way Sepuntih, Desa Kabu Perahu, Kecamatan Balik Bukit, Kabupaten Lampung Barat, Bukit Barisan Selatan National Park, Provinsi Lampung, Sumatra, Indonesia (ca. S 4.866696, E 103.704993, ca. 690 m asl) on 15 November 2005 by Adininggar Ul-Hasanah; with small ovarian eggs and a distended oviduct. UTA A- 62770 (field number ENS 14834), an adult male collected from Desa Kubu Perahu, Kecamatan Balik Bukit, Kabupaten Lampung Barat, Bukit Barisan Selatan National Park, Provinsi Lampung, Sumatra, Indonesia (S 5.06011, E 104.03222, 894 m asl) on 14 June 2013 by Kyle A. O'Connell, Amir Hamidy and E. N. Smith; weight 4 g; 1 m above stream on leaf.

Diagnosis. We place this species in the genus Rhacophorus based on the following characters: tips of digits expanded into large discs bearing circum-marginal grooves; webbed fingers, vomerine teeth present, and a supracloacal dermal ridge ( Rowley et al. 2010). The following combination of characters distinguishes Rhacophorus bengkuluensis from all congeners: (1) The SVL of males is 40.5–46.7 mm and that of females 50.4–57.6 mm. (2) In profile, the snout is rounded in females and slightly sloping towards a low rostral tubercle then sloping back toward the mouth in males; in dorsal view, the snout is round in females and subacuminate in males. (3) The nares are closer to the tip of snout than to the eye. (4) Webbing of the hands is moderate: between fingers I and II reaches proximal subarticular tubercles in females and proximal supernumerary tubercles in males; between fingers II and III reaches base of disk of finger II and distal subarticular tubercle of finger III in both sexes; between fingers III and IV reaches discs in females and more than half way of penultimate phalanges in males. (5) Tubercles or crenulated folds extend along the postaxial margin of the antebrachium and tarsus. (6) One small and conical tubercle is present at each tibio-tarsal articulation, folds absent at this articulation. (7) Dorsum shagreened with few very small and low tubercles; the head and eyelids without tubercles. (8) Supratympanic fold thick and conspicuous extending slightly onto flanks; it overlaps the upper edge of the tympanum and its annulus. (9) The supracloacal ridge is crenulated, low, and white; with white conical tubercles below vent, more numerous and prominent in males. (10) The dorsal ground coloration is brown with darker cross bands; flanks are cream in females and yellow in males, with dark spots present, more prominent in the inguinal area; area below eyes with no prominent spots; males with orange posterior thigh surfaces. The hand and foot webbing is brown, darker postaxially. (11) Peritonea are mostly transparent, with some white coloration on the lower pericardial cavity and transverse septum. (12) Mitochondrial DNA 16S gene sequences (GenBank Nos.: KC701717 and KM212948 ).

Comparisons. The new taxon is most similar to Rhacophorus baluensis , R. harrisoni , R. margaritifer , and R. rufipes . Unlike R. baluensis (character condition in parentheses), females of R. bengkuluensis have full webbing between fingers III and IV (hands half-webbed at most). Unlike R. harrisoni and R. rufipes , R. bengkuluensis has a tibio-tarsal calcar (calcar absent). Our molecular analysis recovered R. bengkuluensis and R. margaritifer as sister taxa ( Fig. 2 ). The 16S sequence is 4.58% divergent from R. margaritifer using uncorrected “p” distances ( Table 2). Unlike R. margaritifer , webbing between fingers III and IV reaches the disk of finger III in females of R. bengkuluensis (webbing only reaches the distal subarticular tubercle). Additionally, female specimens of R. bengkuluensis have a more slender habitus than female specimens of R. margaritifer .

As a medium-size tree frog with extensive light brown hand and foot webbing, R. bengkuluensis is unlikely to be confused with other parachuting frog species found in Sumatra. Unlike R. achantharrhena and R. prominanus , R. bengkuluensis has a reddish brown body and light brown foot webbing (bright green body with red foot webbing). Unlike R. nigropalmatus , R. norhayatiae , R. pardalis , and R. reinwardtii , R. bengkuluensis has light brown hand and foot webbing in life (brightly or distinctly colored hand and foot webbing in life [black, blue, red/ orange, blue/yellow, respectively]) and lacks extremely prominent and scalloped fringes on the outer margins of the hands, forearms, feet and tarsus (highly scalloped margins present). From R. barisani , R. poecilonotus , and R. bifasciatus , R. bengkuluensis differs in lacking a sharply pointed snout in both males and females (pointed in males) and having more webbing between fingers III and IV, reaching close to the base of discs (not past middle of penultimate phalanx of finger III and only reaching near level of distal subarticular tubercle of finger IV). Unlike R. angulirostris , R. catamitus , R. modestus , and R. pseudacutirostris , R. bengkuluensis has extensive hand webbing (moderate hand webbing).

Pairwise comparison % 16S Divergence R. bengkuluensis sp. nov. (MZB.Amph.21194 to UTA A-62770) 1.94

R. bengkuluensis sp. nov. to R. margaritifer 4.93

R. bengkuluensis sp. nov. to R. catamitus 8.82

R. barisani (G. Dempo to G. Kaba; Figs. 1–2 ) 2.64

R. catamitus (G. Dempo to G. Kaba; Figs. 1–2 ) 1.76

R. margaritifer (UTA A-54009 to UTA A-54010) 0.00

R. catamitus to R. gauni 11.06 R. catamitus to R. angulirostris 9.42

Etymology. The specific epithet is an adjective derived from Bengkulu, the origin of the holotype and two paratype specimens, and the Latin suffix – ensis, meaning from that place.

Description of holotype and variation. A brief description of the holotype is included in Harvey et al. (2002) who suspected that the specimen was a female R. catamitus . In addition to reiterating the report of these authors (in brackets) we present our own data and expand on the previous description. Data for the paratypes is presented in parentheses after that of the holotype (variation of males followed by that of females). The specimen has a SVL of 50.4 mm [50.56 reported by Harvey et al.] (40.5–46.7, 50.2–57.6), head length 21.1 mm (13.9–17.2, 17.4–19.2), head width 16.5 mm (14.4–16.5, 17.0–19.0), snout length 7.5 mm (6.8–7.4, 7.8–8.9), internarial distance 4.6 mm (3.2–4.8, 5.0–5.5), eye width 6.7 mm (5.0–5.2, 5.8–7.4), tympanum width 3.2 mm (2.6–3.5, 3.1–3.8), antebrachium length 10.6 mm (7.5–8.1, 10.0–11.9), hand length 17.0 mm (12.9–13.9, 15.6–17.5), thigh length 28.9 mm (21.0–24.1, 26.5–27.8), shank length 31.1 mm (23.6–26.8, 30.0–30.8), foot length 24.3 mm (17.8–19.7, 22.3–24.8).

Body slender; head slightly longer than wide and wider than body; head length 41.8% of SVL (34.3–36.8%, 33.3–36.5%); head width 32.7% of SVL (35.2–35.6%, 32.7–34.1%); snout rounded in profile, without rostral keel; canthus rostralis distinct, elevated and ridge-like; loreal region concave; lips not flared; nostrils ovoid; internarial region concave; top of head mostly flat; diameter of eye 40.3% of head width (31.6–34.9%, 31.6–43.4%); pupil horizontal; palpebral membrane unpigmented; supratympanic fold raised and distinct, extending from posterior portion or orbit ( Fig. 4 ), obscuring upper edge of tympanum, becoming indistinct on posterior side of insertion of forelimb; tympanum distinct and round; tympanum width 48.1% eye width (50.0–69.4%, 41.9–63.3%); axillary membrane present; thoracic fold absent; dermal flap present on postaxial edge of antebrachium; antebrachium slender, fingers slender and bearing expanded, emarginate, and truncate discs; digital grooves ‘V’ shaped and on dorsal surfaces of all fingers, deepest on fingers II–IV; relative length of fingers: I <II <IV <III; relative width of finger discs: I <II <IV <III; palmar tubercle partially divided, about half as large as oval thenar tubercle; subarticular tubercles round, present on all fingers; fingers I–IV respectively with 0, 1, 3, and 4 supernumerary tubercles; heels of adpressed hindlimbs strongly overlapping; small calcar present at tibiotarsal articulation; tarsal fold small, extending entire length of tarsus; thigh length 57.3% of SVL (51.6–51.9%, 48.3–52.8%); shank length 61.7% of SVL (57.3–58.3%, 53.6–60.1%); foot length 48.2% of SVL (42.2–44.0%, 43.1–44.4%); inner metatarsal tubercle, raised, ovoid; outer metatarsal tubercle absent; subarticular tubercles round, present on all toes; supernumerary tubercles barely visible, most visible on Toe IV; toes slender, bearing expanded, emarginated, and truncate discs; digital grooves resembling those on finger discs; relative length of toes: I <II <III <V <IV; relative width of toe discs: I <II <III <IV <V. Webbing between digits extensive on foot [reaching all toe discs] and between certain fingers [reaching discs on preaxial [sic] side of finger II and postaxial [sic] side of finger IV]; full hand webbing formula: I 2–2 ¼ II 1– 2 III 1– 1 IV (males I [2–2½]–[2–2¼] II 1– 2 III 1½– [1–1½] IV; females I [2–2½]–[2–2½] II [1–1¼]– 2 III [1¼–1½]– [1¼ –1½] IV); full foot webbing formula: I 1– 1 II 1– 1 III 1–1¼ IV 1 ¼– 1 V (males I 1 –[1–1½] II 1 –[1½–2] III 1 –[1½–2] IV [1¼–1½]– 1 V; females I 1 –[1–1½] II 1 –[1¼–1½] III 1 –[1½–2] IV 1 ¼– 1 V); anal opening at upper level of thighs, directed posteriorly; cloacal sheath short; ring of small unevenly spaced tubercles surrounding vent; dorsal surface of body and limbs covered in small (0.4–0.8 mm) [scattered, flat, round] tubercles; dorsal skin relatively smooth; skin on venter coarsely granular to smooth (notably smooth in gular region); skin on ventral surfaces of limbs smooth; tongue strongly bifurcated at posterior end, about ⅔ free posteriorly; dentigerous processes of vomer with ten teeth on damaged left side, nine on right side; dentigerous processes transverse, situated at anterior-most position between choanae, widely separated medially; choanae ovoid, widely separated.

Peritonea are mostly transparent with some white coloration on the lower pericardial cavity and transverse septum (slightly more white coloration observed in a male paratype, UTA A-62770).

Coloration of holotype in preservative. Following preservation, all dorsal surfaces are light brown with darker brown transverse bars and blotches. There are two distinct transverse bars on the head, one just behind the nostrils and one more distinct that spans the interocular region ending at the edge of each eyelid. A third line, somewhat faint and broken, lies behind the eyes. All limbs have large dark crossbars with 2, 6, 3, and 2 on the right arm, thigh, shank, and tarsus respectively, and 3, 4, 3, and 1 for the corresponding limb segments on the left side of the body. The scattered small round tubercles covering the dorsum are often black. The venter is a pale cream, speckled with many light brown marks on the limbs and gular region. Above the vent is an amorphous white patch measuring 7.3 mm in width with smaller patches appearing on the posterior surfaces of the dorsum. The posterior lateral surfaces have a notable white reticulated pattern ( Fig. 6 ; A).

Coloration of holotype in life (based on field notes of M.B. Harvey and images UTADC 4031–4032). Holotype ( Fig. 3 ; D and E) clay-brown dorsally with indistinct transverse bands; relatively sharp transition to white on flanks; faint grey blotches on flanks becoming darker in inguinal region; inguinal region reticulated charcoal and cream; venter cream; prominent transverse bars on head dark brown; tympanic membrane nearly same color as dorsal surface; supratympanic fold dark brown; canthus rostralis light tan to orange; limbs light tan to orange with brown bands; calcar and fringes of digits same color as adjacent skin covering limbs; interdigital webbing light gray, without distinctive pattern; each sacral hump with irregular black spots; supracloacal ridge between cloaca and tip of urostyle vibrant orange; dorsal half of the iris pale gold and lower half reddish brown; ciliary ring pale gold.

Intraspecific variation. Several specimens have a thin transverse bar on the snout in addition to the interocular bar. As is typical of many Rhacophorus species, we observed substantial variation in color pattern and head shape among specimens of R. bengkuluensis . In preservative, the dorsal coloration varies from slate grey to dark brown. Males and small adult females, including the holotype, have a truncate snout in dorsal view (based on the terminology of Savage [2002]). In contrast, larger female specimens (MZB.Amph.3449 and 3482) have more flared canthal ridges giving the snout a subovoid appearance in dorsal view. This may indicate that there are shifts in female head shape after a certain body size is reached. Several specimens have similar white reticulations on their posterior lateral surfaces ( Fig. 6 ), similar to the holotype. All specimens possess a white supracloacal ridge in preservative; however, its thickness varies.

Sexual dimorphism. Males are smaller (39–41 mm) in SVL than females (51–62 mm). The ratio of male to female size (ca. ¾) is similar to that observed in R. margaritifer ( Harvey et al. 2002) . Males possess less extensive hand webbing than females, while the extent of foot webbing is comparable. Female specimens have dark flecking on the ventral surface (notably on the gular region), whereas the two males we examined have more or less immaculate ventral surfaces.

Distribution and habitat. Harvey and Smith collected the holotype in rainforest along a stream adjacent to the main highway connecting Kepahiang to Bengkulu, southwestern Sumatra. This mid-elevational locality (600–650 m asl) lies within the Sumatran lowland rainforest ecoregion (Olsen et al. 2001), comprised of tropical and subtropical moist broadleaf forest with higher portions of the ecoregion containing primarily dipterocarps, oaks, and laurels as the habitat transitions into montane rainforest. While we do not possess high resolution georeferences for many of the paratype specimens, the collection localities suggest that R. bengkuluensis occurs throughout most of southwestern Sumatra ( Fig. 1 ). We suspect that the species occurs at low to intermediate elevations (probably between 250 and 900 m asl).

At the time of collection, the holotype appeared to be inactive and was perched on a leaf, 2 m above a stream in the understory of forest. There had been no precipitation on the day the specimen was collected. The recently collected male paratype (UTA A-62770) was perched on a leaf at about one meter above a stream in the forest.

Figures

FIGURE 1. Geographic origin of focal Rhacophorus species examined in this study. Localities for R. catamitus include those reported by Harvey et al. (2002), Inger & Iskandar (2005), and for R. margaritifer those of van Kampen (1923; as R. javanus), Iskandar (1998; as R. javanus; Goa Ngerong records not verified and included), Kurniati (2003; Ujung Kulon records not verified and included), Riyanto (2011), Kusrini (2014) and recent observations by our field parties.

FIGURE 2. Maximum likelihood phylogram generated from a fragment of 16 S mitochondrial DNA. Unless otherwise noted, support values appear above branches and correspond to posterior probabilities (BAYES), maximum likelihood bootstrapping (ML), parsimony bootstrapping (MP), and minimum evolution bootstrapping (ME), respectively. Nodes not receiving topological support are indicated with “ NS ”.

FIGURE 3. Adult male paratype from Lampung (UTA A- 62770; A – C, F and G) and the adult female holotype of Rhacophorus bengkuluensis from Bengkulu province (MZB. Amph. 21194; D and E).

FIGURE 4. Head shape of Rhacophorus bengkuluensis (female holotype, MZB. Amph. 21194).

FIGURE 5. Palmar (left) and plantar (right) surfaces of Rhacophorus bengkuluensis (female holotype, MZB. Amph. 21194). Arrows indicate distinctive features of the hand including extensive webbing between fingers III and IV (A) and a divided palmar tubercle (B).

FIGURE 6. Posterior lateral surfaces of the trunk of Rhacophorus bengkuluensis; female holotype (MZB. Amph. 21194 [left side]; A) and two female paratypes (MZB. Amph. 16308 [left side] and MZB. Amph. 3482 [right side]; B and C, respectively).