Platymantis biak, Siler, Cameron D., Diesmos, Arvin C., Linkem, Charles W., Diesmos, Mae L. & Brown, Rafe M., 2010

Siler, Cameron D., Diesmos, Arvin C., Linkem, Charles W., Diesmos, Mae L. & Brown, Rafe M., 2010, A new species of limestone-forest frog, genus Platymantis (Amphibia: Anura: Ceratobatrachidae) from central Luzon Island, Philippines, Zootaxa 2482, pp. 49-63 : 51-59

Platymantis biak sp. nov.

Figs. 2–4

Holotype. PNM 9679 ( ACD Field No. 4543; KU 319973), adult male, collected on limestone outcrop in secondary-growth forest (20:00 hr) on 17 January 2009 in Barangay Biak na Bato, Municipality of San Miguel and Doña Remedios Trinidad, Bulacan Province, Luzon Island, Philippines (N 15.1084, E 121.0724; 190 m elevation), by ACD

Paratopotypes. Twenty-three males (KU 319977–78, 319981–82, 319987, PNM 9680, 9681, 9682–83, 9684–9697), eight females (KU 319974–75, 319979, PNM 9674–75, 9676, 9677–78), and seven juveniles (KU 319976, 319980, 319983, PNM 9698–9701) collected on karst formations in secondary-growth forest (18:00–23:00), January–March and November 2009, in Barangay Biak na Bato, Municipality of San Miguel and Doña Remedios Trinidad, Bulacan Province, Luzon Island, Philippines; collected by ACD, CDS, CWL, and. MLD.

Diagnosis. We assign the new species to the genus Platymantis on the basis of (1) its moderate body size, (2) absence of interdigital webbing, (3) the presence of a forked omosternum, (4) directly developing reproductive mode, and (5) terrestrial microhabitat preference (Brown and Alcala 1980; Brown et al., 1997; Brown, 2004). Platymantis biak can be distinguished from other Philippine congeners by the following combination of characters: body size 32.3–39.9 mm SVL for males, 37.4–42.4 mm SVL for females; digital disc of Finger III 1.9–2.2 × width of penultimate phalanx in males and 1.4–2.4 in females (Fig. 3); Finger I slightly longer than Finger II; finger discs larger than toe discs; smooth skin; spotted flanks absent; supratympanic fold smooth, less protuberant; tympanum completely visible; dorsolateral stripes absent; dorsal folds, ridges, dermal tubercles absent; and a preference for terrestrial microhabitat in karst forest. Mensural and diagnostic differences are provided in Tables 1 and 2.

Description of holotype. A mature male; habitus robust; head broader than body, head length 35.5% snout–vent length, 90.4% head width; snout protruding moderately beyond lower jaw, snout tip comes to moderately sharp point in dorsal and lateral aspects; eyes moderate and protruding anterolaterally, eye diameter 12.7% snout–vent length, 35.9% head length; lips slightly flared and swollen (Fig. 2); interorbital region slightly convex; eye diameter 80.9% snout length, 134.2% eye–narial distance; pupil horizontally elliptical; canthus rostralis anteriorly concave in dorsal aspect; loreal region moderately concave, sloping ventrolaterally to labium; nostrils oriented posterolaterally; eye–narial distance 60.3% snout length; internarial region slightly concave; tympanic annulus distinct 56.8% eye diameter; supratympanic fold slightly protuberant, extending from posterior corner of eye across dorsal margin of tympanum to supraaxillary region.

Tongue elongate, wider posteriorly, with deep posterior notch and narrow anterior attachment; choanae situated at anterolateral edge of palate, oval, separated by distance two times greater than diameter of single choana; dentigerous process of vomer distinct, with no teeth visible on process; dentigerous process angled slightly anterolaterally, approximately at 20–30º incline with closest (posterior) points separated by distance equal to 2.0 × diameter of single choana, their most distant (anterior) ends separated by distance equal to 3.0 × diameter of single choana.

Hand length 54.6% foot length; tibia length 113.0% foot length, 54.3% snout–vent length; fingers slender, long; terminal discs moderately expanded (Fig. 3A) with pronounced distal, circum-marginal groove; dorsal surfaces of terminal phalanges with small, cutaneous supra-articular flaps between ultimate and penultimate phalanges; relative lengths of fingers II <I <IV <III; subarticular tubercles prominent, convex, smooth; one subarticular tubercle below Digits I and II, two tubercles under Digits III and IV; supernumerary tubercles present at bases of Digits I–IV, distinct, round, prominent for Digits II–IV; inner metacarpal tubercle enlarged, elongate, oval shaped; outer metacarpal tubercle fully divided into round, slightly raised postaxial tubercle equal in size to supernumerary tubercle, and oval preaxial tubercle equal in size to preaxial metacarpal tubercle; nuptial pads absent; forearms slender, not hypertrophied.

FIGURE. 2. Photographs in life of Platymantis biak paratopotypes exhibiting (A) typical limestone-forest frog mottled color pattern, PNM 9678, female, SVL = 40.7 mm, and (B, C) perching behavior observed at type locality, PNM 9674, female, SVL = 40.8 mm. Photographs by A. Diesmos and C. Linkem.

Skin of dorsal and ventral surfaces of head, trunk, and limbs smooth. Terminal discs of toes slightly expanded, with circum-marginal grooves; supra-articular cutaneous flaps above ultimate-penultimate phalangeal articulations; plantar surface of foot smooth, with well-developed, prominently rounded subarticular tubercles (Fig. 3B); supernumerary tubercles absent; relative lengths of toes I <II <V <III <IV; outer metatarsal tubercle small, round; inner metatarsal tubercle moderately prominent, elongate, length 1.7 x length of round, pointed, outer, metatarsal tubercle.

Measurements of holotype (in mm). Snout–vent length 39.9; head length 14.2; head width 15.7; snout length 6.3; upper arm length 9.0; forearm length 9.3; tibia length 21.7; femur length 20.4; tarsus length 9.4; foot length 19.2; hand length 10.5; Finger I length 7.6; Finger III length 7.6; Toe IV length 10.4; eye–narial distance 3.8; snout–narial distance 2.0; interorbital distance 3.3; internarial distance 3.2; eye–tympanum distance 0.8; eye diameter 5.1; horizontal tympanic annulus diameter 2.9; Finger I disc width 1.2; Finger III disc width 1.8; Toe IV disc width 1.2; Finger III penultimate phalange width 0.6; Toe IV penultimate phalange width 0.5.

FIGURE. 3. Ventral views of hand (A) and foot (B) of female paratopotype of Platymantis biak (KU 319974), hand (C) and foot (D) of male Platymantis dorsalis (KU 300356), and hand (E) and foot (F) of male Platymantis guentheri (KU 306324). Scale bar = 2 mm.

Coloration of holotype in preservative. The dominant dorsal color pattern on the head and body consists of dark mottled blotches of black interspersed with blotches of dark shades of brownish green. The dorsal surfaces of the limbs are banded with alternating black and dark green bars, separated by thin tan bands. An interorbital bar is present consisting of a thin, irregular, light-brown line. The head and snout region are darker than the dorsum, and nearly uniform black. A black bar extends across the dorsal half of the canthus rostralis to the anterior edge of eye. The tympanum is medium brownish-green with a dark blotch extending posterodorsally from the center. The temporal region is predominantly black with several small blotches of dark green. Lip coloration consists of alternating dark green and black vertical labial bars, bordered anteriorly by black lower edge of canthal and subocular regions. The transverse bars on the limbs have irregular widths, with an overall lighter coloration when compared to the dorsum due to the greater proportion of skin covered by tan and dark green bands. Arm banding patterns coalesce into mottled patterns on the elbows. Four black bars are present on the forearms, thighs, and tibia, with three bars present on the tarsus. Anterior flank coloration is predominantly black, progressively fading to lighter grayish-tan with dark brown blotches and spots, blending into a black, dark brown, and tan mottled pattern posteriorly. The dorsal surfaces of the hands are light brown, with alternating bands of light brown and grayish-tan on Fingers I–III, and dark brown and grayish-tan on Finger IV. The dorsal surfaces of the feet are colored with alternating bands of light brown and grayish-tan.

The throat and chest are marbled light cream with several small tan speckles, while the periphery of the throat and lower lips are darker, with the anterior edge of the lower lip possessing an irregular outline of dark green blotches. The belly is homogeneous light tan bordered by light cream spots laterally. Ventral coloration on the arms consists of light tan coloration present on the upper arm and interior portions of the forearm, and dark green coloration present on the outer portions of the forearm and hand. Ventral surfaces of the thighs uniformly mottled cream anteriorly and light green-brown posteriorly. This coloration blends gradually down the legs into a homogenous dark brown color pattern on the tarsus and foot, similar to the dark coloration observed on the forearms. The subarticular tubercles of the hands and feet are light cream, and the iris is dark blue-gray around the pupil.

FIGURE. 4. Photographs in preservative of Platymantis biak holotype ( PNM 9679) in dorsal and lateral views of head. Scale bar = 5 mm.

Table 1 . continued.

Coloration in life. Dorsum and head mottled light green, dark green, and black (Fig. 4); interorbital bar distinct, black, and bordered anteriorly by lighter, green-brown border; lower surfaces of supratympanic fold black; black canthal blotch located just anterior to eye; black labial blotch located below eye, anterior to tympanic annulus; dorsal surfaces of limbs with alternating dark brown and green transverse bars, each bordered by thin cream transverse bars; dorsal surface of body with several large black blotches, irregularly distributed; area of black blotches and cream speckles on anterior portion of flanks; pupil bordered by copper ciliary ring of iris, sharply blending into predominant mottled gold and brown color pattern of iris.

biak sp. nov. bayani insulatus spelaeus paengi

(12m, 4f) (9m, 9f) (8m, 6f) (4m, 3f) (15m) SVL (m) 32.3–39.9 34.2–39.1 34.3–38.0 37.1–44.3 27.7–34.3 SVL (f) 37.4–42.4 44.3–49.8 40.2–42.9 53.5– 57.5 N/A

Range Central Luzon Samar Island Gigantes Islands SW Negros NW Panay

Island Island Island Species Group guentheri guentheri guentheri dorsalis dorsalis

Digital disks Moderately Widely Widely Non-expanded Non-expanded

expanded expanded expanded

Dorsal skin rugosity – – to granular – +, – +

Dorsal dermal tubercles – +, sparse – +, small +

Flanks Blotches anteriorly Spotted Spotted Immaculate Spotted Variation. Dominant color pattern consistently mottled in all observed specimens. Variation exists in the w-shaped pattern of pigmentation on the dorsal surface of the body in line with the forearms. Some individuals possess a sharply defined w-shaped pattern (KU 319976, 319980, 319982–83, 319987, PNM 9684–86, 9688–89, 9691, 9693, 9695, 9697, 9700), while the pattern on many other specimens is either obscured by the background body coloration or is vaguely defined (KU 319973–75, 319977–79, 319981, PNM 9698–99, 9680–83, 9674–76, 9687, 9690, 9692, 9694, 9696, 9677–78, 9701, 9704–14). The outer metacarpal tubercle was fully divided in most individuals with the exception of a few individuals showing a single, large, connected outer metacarpal tubercle (KU 319974, 319980, 319981, 319983, 319987). Females are considerably larger and more robust. Summaries of univariate morphological variation in the series are presented in Table 3 .

Distribution. Platymantis biak is known only from the type locality (Fig. 1).

Ecology and natural history. Platymantis biak occurs in secondary-growth forest on karst substrate. Both males and females were observed perched on top of limestone rocks within large rock formations in the forest and around the entrances to cave systems. Additionally, males were observed up to 5 meters inside caves, some perched above the ground within depressions and holes in the karst rock walls (Fig. 2B, C). No specimens were observed perching in trees or shrubs, in contrast to the common behavior of most species in the P. guentheri Group ( Brown and Gonzales, 2007).

Some individuals of Platymantis biak were well camouflaged against the limestone (much like P. bayani , P. insulatus , P. speleaus , and P. paengi ; Fig. 2B, C), and field workers found it difficult to locate and capture individuals against the limestone substrate. This was especially true for many of the females. However, males were often more conspicuous while calling atop rocky outcrops. When disturbed, the new species immediately jumped back into the rocks and escaped into limestone crevices. No egg masses or juveniles were found; other species of Platymantis have direct development ( Brown and Alcala, 1982 a, b). Platymantis spelaeus has been observed by one of us (CDS) to deposit direct-developing eggs in limestone crevices and the same is suspected for P. insulatus ( Brown and Alcala, 2000) . We assume that this species also breeds in limestone crevices and small caves ( Brown and Alcala, 2000; Brown et al., 2003).

Sympatric anuran species include Rhinella marina (introduced), Hoplobatrachus rugulosus (introduced), Kaloula picta , K. pulchra (introduced), Limnonectes macrocephalus , L. woodworthi, Occidozyga laevis, Platymantis cf. mimulus, Polypedates leucomystax, Rana erythraea (introduced), and R. similis .

Etymology. We derive the specific epithet from the Tagalog term biak , meaning "crevice" or "crack," in reference to the preferred limestone karst habitat at the type locality, Biak na Bato (meaning "cracked rock" or "fragmented stone"), Bulacan Province.

Comparisons. The new species is assignable to the P. g u e n t h e r i Group ( P. banahao , P. bayani , P. cornutus , P. diesmosi , P. guentheri , P. insulatus , P. luzonensis , P. negrosensis , and P. rabori ) based on the following combination of characters: digital discs moderately expanded and larger in fingers than in toes, proximal portions of digits with narrow dermal folds in cross section, and subarticular tubercles large and highly protuberant ( Brown et al., 1997 c; Fig. 3).

The new species is morphologically most similar to Platymantis bayani and Platymantis insulatus , the other two members of the P. g u e n t h e r i Group with similar morphology and preference for karst forest microhabitats ( Tables 1 and 2). Platymantis biak is distinguished from P. bayani and P. insulatus by the presence of moderately (vs. widely) expanded digital discs and the absence of fully spotted flanks (vs. spotted). From Platymantis bayani , the new species differs by its smaller female body size (maximum SVL 42.4 mm for P. biak vs. 49.8 mm for P. bayani ), smaller eye diameter (maximum ED 5.2 mm for P. b i a k vs. 6.8 mm for P. bayani ), and the absence of granular skin (vs. absence or presence) and dorsal dermal tubercles (vs. presence). The new species further differs from Platymantis insulatus by the presence of well-defined limb banding patterns (vs. absence or presence and poorly defined). Additional characters for distinguishing the new species from all species of the P. guentheri Group are summarized in Tables 1 and 2.

From all members of the P. d o r s a l i s Group ( P. cagayensis , P. corrugatus , P. dorsalis , P. indeprensus , P. levigatus , P. mimulus , P. naomiae , P. paengi , P. pseudodorsalis , P. pygmaeus , P. spelaeus , and P. t a y l o r i), Platymantis biak is distinguished by the presence (vs. absence) of moderately expanded digital discs (Fig. 3) and larger finger discs than toe discs. Platymantis biak is further distinguished from all members of the P. dorsalis Group, except P. levigata by the absence of dorsal folds and ridges, dermal tubercles, and rugose skin (vs. presence of one, two, or all characters), and from all members except P. paengi and P. spelaeus , by its microhabitat preference (terrestrial substrates in limestone forest vs. leaf litter of forest floor and/or herb-layer vegetation in P. cagayensis , P. corrugatus , P. dorsalis , P. indeprensus , P. mimulus , P. naomiae , P. pseudodorsalis , P. pygmaeus and P. t a y l o r i, or river banks and rocks in P. levigatus ). From P. cagayensis , P. corrugatus , P. dorsalis , P. indeprensus , P. mimulus , P. naomiae , P. pygmaeus and P. t a y l o r i, the new species is distinguished by the absence (vs. presence) of dorsal folds and ridges.

The new species is distinguished from all P. hazelae Group species ( P. hazelae , P. isarog , P. lawtoni , P. montanus , P. panayensis , P. polillensis , P. sierramadrensis , P. subterrestris ) by its larger body size; the first finger slightly longer than the second; narrow dermal phalanges on the digits; protuberant (vs. flattened) subarticular tubercles, and a preferred microhabitat of terrestrial substrates in limestone forest (vs. arboreal habitat, and/or shrub-layer vegetation).

Tables

TABLE 1. Summary of qualitative diagnostic characters (present, absent) in Platymantis biak and specimens of other members of the P. guentheri Species Group. Sample size for each sex, body size, eye diameter, digit disk proportions, and general geographical distribution (PAIC = Pleistocene Aggregate Island Complexes, sensu Brown and Diesmos, 2002) are included for reference (SVL and ED given as range over mean ± standard deviation; digit disk proportions given as percentage over mean ± standard deviation). Only adult specimens in good preservation condition were used for morphometric analyses.

	biak sp. nov. (24m, 8f)	bayani (9m, 9f)	insulatus (8m, 6f)	negrosensis (3m, 2f)	luzonensis (9m, 2f)
Range	Central Luzon Island	Samar Island	Gigantes Islands	Negros and Panay Islands	Luzon PAIC
SVL (m) SVL (f)	32.3–39.9 (35.9 ± 1.8) 37.4–42.4 (40.1 ± 1.5)	34.2–39.1 (37.1 ± 1.8) 44.3–49.8 (46.4 ± 2.1)	34.3–38.0 (36.7 ± 1.3) 40.2–42.9 (41.8 ± 1.0)	28.3–35.7 (31.1 ± 4.0) 41.7–42.2 (42.0 ± 0.3)	24.1–32.5 (29.7 ± 2.4) 32.6–33.8 (33.2 ± 0.8)
ED (m) ED (f)	3.3–5.2 (4.3 ± 0.5) 4.3–5.2 (4.9 ± 0.3)	4.8–6.1 (5.5 ± 0.5) 5.4–6.8 (6.1 ± 0.4)	3.7–4.9 (4.2 ± 0.4) 5.1–5.7 (5.3 ± 0.2)	3.1–4.1 (3.7 ± 0.6) 4.4–4.7 (4.6 ± 0.2)	2.7–3.9 (3.4 ± 0.4) 3.6–3.9 (3.7 ± 0.2)
Fin3DW/PpFin3 (m) Fin3DW/PpFin3 (f)	1.4–3.4 (2.1 ± 0.5) 1.4–2.7 (2.2 ± 0.4)	2.7–4.0 (3.3 ± 0.4) 2.8–4.5 (3.9 ± 0.5)	2.7–3.1 (2.9 ± 0.1) 2.3–2.8 (2.7 ± 0.2)	2.6–2.8 (2.7 ± 0.1) 3.5–4.7 (4.1 ± 0.8)	2.2–3.3 (2.8 ± 0.4) 3.0–3.2 (3.1 ± 0.2)
Toe4DW/PpToe4 (m) Toe4DW/PpToe4 (f)	1.3–2.4 (1.7 ± 0.3) 1.6–3.1 (2.1 ± 0.5)	2.1–3.3 (2.8 ± 0.4) 2.9–3.7 (3.1 ± 0.3)	1.9–3.4 (2.6 ± 0.4) 2.0–2.6 (2.3 ± 0.3)	1.8–1.9 (1.8 ± 0.1) 1.8–1.8 (1.8 ± 0.0)	1.6–2.2 (1.9 ± 0.2) 1.8–1.9 (1.8 ± 0.1)
Fin3DW/ Toe4DW (m) Fin3DW/Toe4DW (f)	0.9–1.7 (1.2 ± 0.2) 0.9–1.4 (1.2 ± 0.2)	1.1–1.5 (1.3 ± 0.1) 1.2–1.5 (1.3 ± 0.1)	1.1–1.5 (1.3 ± 0.1) 1.2–1.6 (1.4 ± 0.1)	1.8–2.0 (1.9 ± 0.1) 1.7–2.0 (1.9 ± 0.3)	1.6–2.0 (1.7 ± 0.1) 2.0–2.1 (2.1 ± 0.1)
Greatly expanded digital disks	+, moderate	+	+	+	+
Dorsal skin rugosity	–	– to granular	–	+	+
Dorsal dermal tubercles	–	+, sparse	–	+	+
Tubercle color	N/A	Salmon	N/A	Cream	Dominant dorsal color
Dorsal folds/ridges	–	–	–	+	+
Tympanum hidden	No	No	No	Posterodorsal edge	Posteroventral edge
Supratympanic fold	Smooth, less prominent	Smooth, less prominent	Smooth, not prominent	Rugose, prominent	Rugose, prominent
Dorsolateral stripes	–	–	–	+	+ or –
Spotted flanks	–, blotches anteriorly	+	+	–	–
Limb bands	+, well defined	+, well defined	+ or –, poorly defined	+, well defined	+, well defined
Microhabitat preference	Ground, karst habitat	Ground; karst habitat	Ground; karst habitat	Arboreal	Arboreal

TABLE 3. Summary of univariate morphological variation among mensural characters in the type series of Platymantis biak.

	Female n = 8	Male n = 24
SVL	37.4–42.4 (40.1 ± 1.5)	32.3–39.9 (35.9 ± 1.8)
HL END	14.9–17.3 (15.7 ± 0.7) 3.8–4.4 (4.1 ± 0.2)	11.8–16.0 (13.6 ± 0.9) 3.2–3.9 (3.6 ± 0.2)
SNL	5.9–7.2 (6.6 ± 0.6)	5.1–6.4 (5.9 ± 0.4)
IOD IND	3.1–4.3 (3.6 ± 0.4) 3.0–4.0 (3.6 ± 0.4)	2.6–4.2 (3.4 ± 0.4) 2.6–3.6 (3.2 ± 0.3)
ED	4.3–5.2 (4.9 ± 0.3)	3.3–5.2 (4.3 ± 0.5)
TAD ETD	3.3–4.3 (3.8 ± 0.3) 0.5–1.5 (0.8 ± 0.3)	2.7–4.0 (3.4 ± 0.3) 0.3–1.4 (0.7 ± 0.2)
HW	15.1–17.2 (16.1 ± 0.7)	12.5–15.7 (14.1 ± 0.9)
UA FAL	7.9–9.6 (8.6 ± 0.6) 9.4–11.2 (10.0 ± 0.6)	7.2–9.7 (8.5 ± 0.7) 7.9–10.3 (9.2 ± 0.7)
FL	18.8–22.0 (20.7 ± 0.9)	16.7–21.0 (18.8 ± 1.2)
TBL TSL	20.0–23.6 (21.0 ± 1.1) 10.3–18.6 (12.3 ± 2.7)	16.7–21.7 (19.0 ± 1.4) 9.4–12.5 (10.8 ± 0.9)
PL	11.3–19.4 (17.8 ± 2.7)	14.7–20.4 (17.5 ± 1.5)
ML Toe4 L	10.3–12.1 (11.1 ± 0.6) 10.8–13.4 (12.1 ± 0.8)	7.8–12.4 (10.2 ± 1.1) 9.6–12.8 (11.4 ± 1.0)
Fin1L	5.4–7.3 (6.3 ± 0.8)	4.1–7.6 (5.5 ± 0.9)
Fin3L Fin1DW	7.6–8.8 (8.1 ± 0.5) 0.8–1.2 (1.1 ± 0.1)	6.5–8.6 (7.6 ± 0.5) 0.8–1.2 (0.9 ± 0.1)
Fin3DW	1.3–1.9 (1.6 ± 0.2)	0.1–1.2 (1.3 ± 0.2)
Toe4 DW PpFin3	1.0–1.5 (1.3 ± 0.2) 0.5–0.9 (0.7 ± 0.1)	0.7–1.3 (1.1 ± 0.2) 0.4–0.9 (0.7 ± 0.1)
PpToe4	0.4–0.9 (0.7 ± 0.2)	0.5–0.8 (0.7 ± 0.1)