Bioacoustics of Platymantis quezoni

Distribution. Platymantis quezoni is known only from the type locality but may be more wide spread in scattered karst outcrops of northern portions of the Bicol Peninsula ( Restificar et al. 2006 ; MGB 2010 ), especially on limestone karst formations in the nearby Bondoc Peninsula ( Fig. 1 ). Ecology and natural history. Platymantis quezoni occurs in mature secondary-growth and mixed secondary growth combined with original forest, on the limestone karst substrates of Quezon Protected Landscape and most likely in other surrounding areas ( Fig. 1 ). Both males and females were frequently encountered climbing vertical limestone rock faces, on narrow shelves of limestone at the base of karst cliffs, perched on top of large limestone boulders, in cracks and crevices, and around the entrances to small caves ( Fig. 5 B). No specimens were observed climbing on vegetation growing from limestone, in contrast to the common scansorial habits of species of the other members of the subgenus Lupacolus ( Brown et al. 1997 a , b ; Alcala & Brown, 1999 ; Brown & Gonzales, 2007 ). Sympatric but non-syntopic anuran species include Rhinella marina ( Bufonidae , introduced), Hoplobatrachus rugulosus ( Dicroglossidae , introduced), Kaloula pulchra ( Microhylidae , introduced), K. picta , and K. conjuncta ( Microhylidae , native & endemic to the Philippines ), Limnonectes macrocephalus , L. woodworthi , Occidozyga laevis ( Dicroglossidae , native & endemic), Sanguirana luzonensis ( Ranidae , native & endemic), Rhacophorus pardalis and Polypedates leucomystax ( Rhacophoridae , native, non-endemic). Syntopic native endemic species (collected in the immediate vicinity or adjacent microhabitats) include P. ( Lupacolus ) dorsalis , P. ( Platymantis ) corrugatus , P. ( Tahananpuno ) luzonensis , Platymantis ( Lupalolus ) n. sp. 14 (Brown et al . 2015) ( Ceratobatrachidae ), Kaloula picta , and K. cf. kalingensis (Microhylidae) . Advertisement call. At the type locality, when visited in dry-season months (December and January), calling activity was heard during and following rainfall; in the rainy months of July through September, the new species called continuously in the afternoon and early evenings. Advertisement calls were recorded on two visits to the type locality, at ambient temperatures of 22.5–22.6°C on the first occasion ( 27–28 November 2001 ), and 23.1°C on our second visit. ( 9 January 2011 ). The following description is based on vouchered calls of seven collected males ( PNM 9817, holotype ; TNHC 61989–92, KU 328735, 328736, paratypes ). Neither ambient noises of wind in the canopy of mature forest in the area, nor advertisement calls of congeners ( P. dorsalis calls frequently at this locality) disrupted the activity of calling male P. quezoni . Calling activity begins in the late afternoon (16:30–17:30 hr) and typically lasts 3–5 hr. In the late afternoon, frogs call intermittently from relatively deep inside limestone crevices, or from within small caves. As the forest becomes darker, additional males begin calling and eventually can be seen on the surface of limestone, or calling from just inside crevices. As more individuals move to exposed perches, calling around limestone aggregations reaches maximal intensity. Periods of intense calling energy are separated by 30–120 s of silence, before males call again. Because all our recordings were made at the same locality, at very similar temperatures, and in almost identical atmospheric conditions (immediately following a heavy late afternoon rain), no temperature corrections were undertaken for this description. Female Male n = 4 n = 16 Snout–Vent Length 32.4–39.7 (37.8 ± 2.7) 22.1–33.9 (29.9 ± 4.9) Head Length 14.3–14.3 (15.8 ± 1.0) 9.4–15.1 (12.4 ± 2.6) Snout Length 5.3–7.3 (6.5 ± 0.9) 4.7–6.6 (5.7 ± 0.7) Interorbital Distance 3.0–3.5 (3.4 ± 0.2) 1.9–3.0 (2.6 ± 0.4) Internarial Distance 2.4–3.5 (3.0 ± 0.5) 1.9–3.7 (2.3 ± 0.4) Eye Diameter 5.0–6.0 (5.5 ± 0.4) 3.5–5.2 (4.4 ± 0.7) Tympanic Annulus Diameter 3.1–3.6 (3.3 ± 0.2) 1.9–3.1 (2.6 ± 0.5) Eye–Tympanum Distance 0.5–1.5 (0.8 ± 0.3) 0.3–1.4 (0.7 ± 0.2) Head Width 14.8–17.2 (16.4 ± 1.1) 9.2–14.3 (11.9 ± 2.4) Upper Arm Length 6.2–8.4 (7.6 ± 0.9) 4.3–6.8 (5.2 ± 0.9) Forearm Length 8.9–10.9 (10.2 ± 0.9) 5.5–9.4 (7.7 ± 1.4) Femur Length 15.4–21.7 (19.4 ± 2.7) 10.5–17.4 (14.7 ± 2.9) Tibia Length 18.3–23.4 (21.3 ± 2.4) 13.0–19.1 (16.8 ± 2.6) Tarsus Length 10.2–13.0 (12.0 ± 1.2) 7.4–11.4 (9.6 ± 1.7) Foot Length 18.2–23.9 (22.0 ± 2.6) 12.8–19.4 (16.6 ± 2.8) Hand Length 9.8–12.8 (11.5 ± 1.2) 6.7–10.0 (8.6 ± 1.4) Toe 4 Length 11.8–15.0 (14.2 ± 1.6) 8.8–12.7 (11.3 ± 1.5) Finger 1 Length 4.4–6.3 (5.6 ± 0.8) 2.8–5.2 (4.0 ± 1.1) Finger 3 Length 6.4–8.4 (7.7 ± 0.9) 4.1–6.6 (5.5 ± 1.1) Finger 1 Disc Width 0.6–1.2 (0.9 ± 0.3) 0.5–1.2 (0.8 ± 0.3) Finger 3 Disk Width 0.8–1.6 (1.2 ± 0.3) 0.1–1.2 (1.3 ± 0.2) Toe 4 Disc Width 1.0–1.6 (1.3 ± 0.2) 0.6–1.3 (0.9 ± 0.2) Penultimate Phalanx Width, Finger 3 0.4–0.6 (0.5 ± 0.1) 0.3–0.5 (0.4 ± 0.1) Penultimate Phalanx Width, Toe 4 0.5–0.8 (0.6 ± 0.1) 0.4–0.6 (0.5 ± 0.1) Males produce a largely invariant and unique advertisement call, sounding to the human ear like a long continuous series of low-frequency one-syllable barking notes ranging from: “yox, yox, yox…” to “iyohk, iyohk, iyohk …” Male calling behavior continues for up to several minutes of uninterrupted, steadily paced vocalizations. Calling begins when a previously resting male takes a more erect posture, raises the head, and takes several inhalations, buccal pumping while filling the lungs. The male then calls with a single note (described below) on expiration by contraction of body wall musculature, which fills the vocal sac. The elastic vocal sac then recoils, forcing air back into the lungs, with the process repeats over a series of up to a few minutes, with air being shuttled back and forth between the vocal sac and the lungs, and the multi-note call lasting a minute or more. Calls were separated by intervals of 12–78 ( x = 31.3 ± 22.7 SD; n = 13 x ) s. Note repetition rate ([total number of notes – 1]/ time from beginning of first note to beginning of last) ranged from 0.37–1.17 ( x = 0.80 ± 0.28 SD; n = 7) notes/s. Apart from a slightly slower initial “warm-up” of a few seconds, no modulation of note repetition rate was detected across the call, and inter-note intervals were slightly variable, but not predictably so. Individual notes have a complex structure of three main elements ( Fig. 6 A,D), some of which are so brief that the call’s complex structure is nearly indiscernible to the human ear. Each note consist of a brief prefix, a second, croaking, main syllable, and a brief suffix differing from the prefix ( Fig. 6 A). In the majority of calls, the prefix takes the form of a tonal frequency arc, which rapidly climbs from an initial frequency of approximately 2.2–2.6 ( x = 2.4 ± 0.08 SD; n = 7) kHz, reaches a maximum at 2.8–3.2 ( x = 2.9 ± 0.11 SD; n = 7) kHz, and then declines in a mirror-image fashion over a period of 30–41 ( x = 34 ± 4.3 SD; n = 7) ms. The final frequency of this variable tonal prefix (in most instances a full tonal arc, in others more of a decreasing frequency sweep) is identical in apparent range and peak frequency to the upper frequency of the call’s second syllable ( Fig. 6 D). The second element, approximately 3–3.5 x duration of the first, is a harsh croaking syllable composed of two nearly equal intensity non-modulated frequency bands ( Fig. 6 A,D). The two constant-frequency components consist of a lower fundamental frequency band spanning 0.9–1.7 kHz and an upper (dominant) frequency ranging across 2.2–2.8 kHz. Peak frequencies of these components varied from 2.25 to 1.4 ( x = 1.3 ± 0.05 SD; n = 7) kHz for the first band and 2.5 to 2.8 ( x = 2.6 ± 0.09 SD; n = 7) kHz in the second. The third note element is a highly variable tonal suffix, again typically of the same frequency as the upper frequency band of the main, second croaking syllable, and is a variable tonal ascending sweep which, like the call’s prefix, typically sweeps from ~2.4 to 2.9 kHz ( Fig. 6 D). The spectral structure of notes ( Fig. 6 A,D) consists of a pair of nearly equally emphasized frequencies (the lower, fundamental, and the upper, which is the first multiple of the fundamental). The FFT (power spectrum) demonstrates that the majority of energy in each call is found in the second frequency component (the dominant frequency, in contrast to the lower, fundamental frequency). Finally, the calls of P. quezoni have complex spectral structure ( Fig. 6 D), with two detectable harmonics in most recordings and three in at least one call (TNHC 61990).

Diagnosis. Platymantis quezoni , sp. nov. , can be distinguished from other Philippine congeners by the following suite of characters: body size 22.1–33.9 mm SVL for males, 33.8–39.7 mm for females; terminal discs of fingers and toes slightly expanded ( Fig. 2 A,B); Finger I longer than Finger II; fingers and toes lacking dermal flanges along sides of digits, subarticular tubercles large and highly protuberant ( Fig. 2 A,B); skin smooth, but with scattered and raised dermal tubercles ( Figs. 3 , 4 ); dorsolateral folds, mid-dorsal ridges, and other cephalic protuberances absent; color pattern medium to dark brown with black spots ( Fig. 3 ); advertisement call a series of invariant low-frequency stridulated one-syllable barks: “Iyohk, iyohk, iyohk…” ( Fig. 6 ) and its restriction to terrestrial microhabitats in forest covering limestone karst formations ( Fig. 5 ). Diagnostic character state differences are summarized in Table 1 and we provide detailed comparisons, emphasizing diagnostic differences between the new species and its close relatives below. Comparisons. We assign the new species to the subgenus Lupacolus Brown et al. 2015 on the basis of its placement (as “ Platymantis sp. 27”) in Clade R of the genus Platymantis (Brown et al . 2015: Fig. 2 ). The subgenus Lupacolus is largely equivalent of the former P. dorsalis Group of Brown et al. (1997a) and Alcala & Brown (1999) , and contains the named taxa P. cagayensis , P. dorsalis , P. indeprensus , P. mimulus , P. naomiae , P. paengi , P. pseudodorsalis , P. spelaeus , and P. t a y l o r i but does not include P. biak , P. levigatus , P. pygmaeus (placed in subgenus Lahatnanguri ; Clade O of Brown et al. 2015: Fig. 2 ) or P. corrugatus (subgenus Platymantis , clade name Tagomukhus; Clade N of Brown et al . 2015: Fig. 2 ). Members of the genus Platymantis , subgenus Lupacolus , all possess the following combination of characters: body size moderate (~ 25–45 mm SVL in males); digital discs non-expanded to minimally expanded; first finger longer than second; fingers and toes lacking dermal flanges along sides of digits; subarticular tubercles large and highly protuberant ( Brown et al. 1997 a , c ; Alcala & Brown 1999 ; Fig. 3 ). In overall phenotypic similarity Platymantis quezoni most resembles the related species P. paengi , P. spelaeus , (all three belong to the subgenus Lupacolus ), the unrelated P. biak , P. insulatus (both of the subgenus Lahatnanguri ), and P. bayani (subgenus Tahananpuno ). All six taxa share the general mottled limestonecamouflaged color pattern and all exclusively inhabit limestone karst microhabitats. Platymantis quezoni shares with the other members of the subgenus Lupacolus ( P. paengi , P. spelaeus ) minimally expanded terminal digital discs, whereas these two species of subgenus Lahatnanguri ( P. biak , P. insulatus ), and all members of the subgenus Tahananpuno (including P. bayani ) have widely expanded terminal discs of the fingers and toes ( Brown & Alcala, 1970 ; Brown et al . 1997a , c ; Siler et al. 2009 , 2010). Additionally, P. bayani , P. insulatus , and P. spel aeus further differ by their much larger body sizes, which do not overlap the size range of P. quezoni ( Table 1 ). Finally, the advertisement call of the new species (a rapid series of loud, harsh, single-syllable barks) differs from that of P. biak (a much slower, low amplitude series of tonal notes), P. insulatus (a long clicking train of brief atonal pulses), P. spelaeus (a four-syllable, multinote complex call) and P. paengi (tonal, frequency sweep, amplitude modulated call). Platymantis quezoni is distinguished from the remaining members of the subgenus Tahananpuno ( P. diesmosi , P. luzonensis , P. negrosensis , P. guentheri , and P. rabori ) by the presence of minimally expanded (vs. widely expanded) terminal digital discs of the fingers and toes. The terrestrial limestone karst microhabitat of P. quezoni further distinguishes the new species from all of these arboreal tree frog taxa except P. d i e s m o s i (a terrestrial species calling exclusively from cliff ledges on Mt. Malino; Brown & Gonzales 2007 ) and its advertisement call likewise distinguishes P. quezoni from the tree frogs with amplitude modulated calls ( P. luzonensis , P. negrosensis , and P. rabori ) and P. guentheri , an arboreal species with a tonal, frequency sweep call. The new species is distinguished from all species of Philippine cloud frogs (formerly the P. ha z e l a e Group species) of the subgenus Tirahanulap ( P. hazelae , P. isarog , P. lawtoni , P. montanus , P. panayensis , P. polillensis , P. sierramadrensis , and P. subterrestris ) by its larger body size (vs. much smaller in these species, typically ~ 20–28 mm in males), by unadorned digits (vs. digits with wide dermal fringes), by strongly protuberant (vs. ventrally flattened) subarticular tubercles, by possessing a longer first finger than the second (vs. second longest) and its terrestrial limestone karst microhabitat (vs. shrub-layer vegetation of montane forests). Species of the subgenus Tirahanulap all possess tonal, constant frequency calls with complex harmonic structure, contrasting sharply with the loud, harsh barking calls of P. quezoni . From remaining members of the subgenus Lupacolus (previously referred to as the Platymantis dorsalis Group) ( P. cagayensis , P. dorsalis , P. indeprensus , P. mimulus , P. naomiae , P. pseudodorsalis , and P. tayl ori ), P. quezoni is distinguished by from all species except P. levigatus by the absence of dorsal folds and/or ridges, and limitation of dermal tubercles to its eyelids (vs. presence dermal folds/ridges and widely distributed tubercles over most dorsal body surfaces), and from all Lupacolus except P. paengi and P. s p e l a e us, by its terrestrial limestone forest microhabitat (vs. much more generalist inhabitant of leaf litter of forest floor and/or herb-layer vegetation in P. cagayensis , P. dorsalis , P. indeprensus , P. mimulus , P. naomiae , P. pseudodorsalis , and P. t a yl or i ). Other than P. dorsalis and P. pseudodorsalis (which possess frequency sweep calls), these species possess complex, multisyllable call structure, which contrasts markedly with the simpler, single-syllable barking calls of P. quezoni . The new species differs from Platymantis corrugatus (subgenus Platymantis , clade name Tagomukhus) by its smooth to shagreened skin texture (vs. dorsal skin with elongate dermal folds), by its lateral head coloration similar to other dorsolateral surfaces (vs. presence of a dark “mask” coloration on the lateral side of the head of P. corrugatus ) and by its exclusive limestone karst microhabitat (vs. a variety of terrestrial forest types ). The advertisement call of P. quezoni is surprisingly quite similar to that of P. corrugatus (a loud series of single “quacks”) except that P. corrugatus is generally crepuscular whereas P. qu e z o ni calls beyond sunset and well into night-time hours if precipitation is sufficient. The final set of comparisons for the recognition of P. quezoni is to the group of species comprising a recently discovered clade for which the subgenus Lahatnanguri was established (Brown et al. 2015). The new species differs from tree frogs of this clade by its terrestrial limestone karst microhabitat and possession of minimallyexpanded terminal discs of the fingers and toes (vs. widely expanded discs in the arboreal species P. banahao , P. cornutus ), from the forest floor leaf litter-inhabiting, miniature species P. pygmaeus (SVL 13–16 mm in males) by its much larger body size ( 22–34 mm ) and limestone karst microhabitat, and from the semi-aquatic species P. levigatus by its light brown, mottled dorsal coloration (vs. dark, more uniformly colored dorsum), by its drier, limestone karst microhabitats (vs. moist, riparian environments). Finally, P. quezoni differs from the limestone karst frogs of the subgenus Lahatnanguri by its minimally-expanded terminal discs of the fingers and toes (vs. markedly expanded in P. biak , and widely expanded in P. insulatus ), the presence of distinct transverse banding patterns of the thigh and tibia (vs. absent or vague in P. insulatus ), and its simple, single-syllable barking calls advertisement call (vs. atonal clicking pulses in P. insulatus and the slow series of low, tonal notes in P. biak .)