Hyloscirtus hillisi, Ron, Santiago R., Caminer, Marcel A., Varela-Jaramillo, Andrea & Almeida-Reinoso, Diego, 2018

Ron, Santiago R., Caminer, Marcel A., Varela-Jaramillo, Andrea & Almeida-Reinoso, Diego, 2018, A new treefrog from Cordillera del Condor with comments on the biogeographic affinity between Cordillera del Condor and the Guianan Tepuis (Anura, Hylidae, Hyloscirtus), ZooKeys 809, pp. 97-124 : 102-111

Hyloscirtus hillisi sp. n.

Holotype.

QCAZ 68649 (Figs 5-7), field no. SC 59176, adult female from Ecuador, Provincia Morona Santiago, Caverns-cascade trail, Reserva Biológica El Quimi, on the slopes of flat-topped mountain on the eastern side of the Río Quimi valley (3.5190S, 78.3788W), 2128 m above sea level, collected by Diego Almeida, Darwin Núñez, Kunam Nucirquia, Alex Achig, and Ricardo Gavilanes on 8 July 2017.

Paratopotypes.

QCAZ 68646, 72549 subadult females, 68651-54, 72552, tadpoles, 69001, metamorphs, 72550, 72553, adult males, 2112-2134 m of elevation. Collected on 7-14 July 2017 and 12-19 April 2018 by Diego Almeida, Darwin Núñez, Kunam Nucirquia, Alex Achig, Ricardo Gavilanes, and María del Mar Moretta.

Paratypes.

All specimens from Reserva Biológica el Quimi, eastern side of the Río Quimi valley, Provincia Morona Santiago, Ecuador. Base camp surroundings, near Río Cristalino (3.5183S, 78.3914W), 1992 m, QCAZ 68647, juvenile, 68648, 68650, metamorphs, 68655-56, 71182, tadpoles collected on 4, 8-9 July 2017; second plateau, near limestone cave (3.5189S, 78.3815W), 2121 m, QCAZ 72551, adult male, collected on 19 April 2018. Collected by Diego Almeida, Darwin Núñez, Kunam Nucirquia, Alex Achig, and Ricardo Gavilanes.

Diagnosis.

The diagnosis and comparisons are based on one adult female, three adult males, and two subadult females. The new species is diagnosed by the following characters: mean SVL 70.3 mm in adult males (range 66.7-72.3; n = 3), 65.8 mm in one adult female; vomerine odontophores conic-shaped with a gap medially, each process with three to five prominent teeth; supracloacal flap ill-defined; supratympanic fold present; finger webbing formula: I basal II2--3-III 2½ -2IV, toe webbing formula: I2--2II1+-2+III 1½-2½IV2½ -1+V; forelimbs hypertrophied in males; enlarged and curved prepollex protruding as a spine in both sexes; fleshy calcar absent; dorsum, flanks, and dorsal areas of limbs dark grayish brown with tiny orange marks varying from abundant to sparse; venter dark grayish brown; iris bronze or yellowish with dark brown reticulation.

Comparisons.

Hyloscirtus hillisi is most similar to H. condor , H. diabolus , and H. tapichalaca (Figure 4). They share the presence of an enlarged claw-like prepollex. Hyloscirtus condor differs in ventral coloration (light gray to light salmon in H. condor vs. dark brown in H. hillisi ) and dorsal coloration (brown dorsum with diffuse yellow speckling in H. condor vs. dark brown dorsum with contrasting orange round marks in H. hillisi ). Hyloscirtus diabolus differs from H. hillisi by having a red iris (bronze or yellowish with brown reticulations in H. hillisi ) and a fleshy calcar (calcar absent in H. hillisi ; Rivera-Correa et al. 2016). Hyloscirtus tapichalaca differs from H. hillisi by having a brown dorsum without orange marks (orange marks present in H. hillisi ) and white disks on fingers and toes (disks are dark brown in H. hillisi ). The remaining species of the H. larinopygion group lack the enlarged claw-like prepollex ( Ardila-Robayo et al. 1993; Mueses-Cisneros and Anganoy-Criollo 2008; Mueses-Cisneros and Perdomo-Castillo 2011; Ruiz-Carranza and Lynch 1982; Rivera-Correa et al. 2016).

Description of the holotype.

An adult female (Figs 5-7), 65.78 mm SVL. Head round in dorsal view, wider than long; snout nearly truncate in lateral and dorsal views; distance from nostril to eye shorter than diameter of eye; canthus rostralis rounded; loreal region slightly concave; internarial region nearly flat; top of head slightly concave; nostrils slightly protruding anterolaterally; lips rounded, not flared; interorbital area slightly convex; eye large, protuberant; diameter of eye 1.85 times diameter of tympanic annulus; supratympanic fold thick, curved, covering posterodorsal edge of tympanum, extending from eye to posterior end of mandible and to shoulder; tympanum rounded; tympanic annulus distinct, rounded, separated from eye by ca. 1.43 times its diameter.

Forearms robust compared to upper arms but not hypertrophied; axillary membrane absent; ulnar tubercles absent; relative length of fingers I <II <IV <III; fingers bearing large, oval discs, wider than finger; subarticular tubercles prominent, round to ovoid, single; supernumerary tubercles present, small and rounded; thenar tubercle, elliptical; palmar tubercle round; prepollical tubercle large, elliptical; prepollex enlarged, claw shaped; webbing formula of fingers I basal II2--3-III 2½ -2IV (Fig. 7).

Toes bearing discs broadly expanded, rounded and slightly smaller than those of fingers; relative length of toes I <II <III <V <IV; inner metatarsal tubercle large, oval; outer metatarsal tubercle absent; subarticular tubercles single, round, large, and protuberant; supernumerary tubercles present; toes webbing formula I2--2II1+-2+III 1½-2½IV2½ -1+V (Fig. 7).

Skin on dorsum, flanks, dorsal surfaces of limbs, throat, chest, dorsal, and inner surfaces of thighs smooth; belly and ventral surfaces of thighs areolate, those of shanks smooth. Cloacal opening directed posteriorly at upper level of thighs, round tubercles below and of vent. Tongue slightly cordiform, widely attached to mouth floor; vomerine odontophores conic-shaped, separated medially, behind level of ovoid choana; each bearing 3-5 vomerine teeth. Additional measurements of the holotype are listed in Table 3.

Color of holotype in preservative.

(Figure 6). Dorsal surfaces of head, body, and limbs, including fingers, dark grayish-brown densely stippled with minute, cream flecks. Ventral surfaces of limbs and belly grayish-brown, ventral surfaces of discs, webbing, chest, and throat paler.

Color of holotype in life.

(Figure 5A). Based on digital photographs. Dorsal surfaces same as above except that flecks are bright orange. Ventral surfaces are dark grayish-brown. Ventral pads of digital discs on fingers and toes are gray. Iris is yellowish-cream.

Variation.

Dorsal and ventral variation of preserved individuals is depicted in Figure 6. Morphometric variation is shown in Table 3. In preservative, dorsum varies from dark grayish-brown (e.g., QCAZ 68646) in adults to pale grayish-brown (e.g., QCAZ 68647, 68650) or pale gray (e.g., QCAZ 68648) in juveniles and metamorphs. Scattered minutes cream flecks can be present on dorsal surfaces (e.g., QCAZ 68646, 68647). Specimen QCAZ 68647 (juvenile) has cream transverse bars on the dorsal surfaces of the limbs (two to four on the forearm and five to seven on the thigh, shank, and foot). Ventral surfaces vary from pale grayish-brown (e.g., QCAZ 68646) to pale brown or cream (e.g., QCAZ 68648, 68650). Coloration of webbing and discs vary from dark grayish-brown to pale grayish-brown or gray.

In life, (Figure 5), the adult specimens are very similar to the holotype except for the density of bright orange flecks (bright yellow in situ; Figure 11A) on the dorsal surfaces. Background dorsal coloration in juveniles and metamorphs (Figure 8) varies from mottled or uniformly brown (e.g., SC 59268, QCAZ 68650) to light brown (e.g., QCAZ 68648) with or without orange-brown transversal bars on the dorsal surfaces of the limbs. Ventral surfaces vary from dark grayish-brown to cream (e.g., SC 59268). Iris varies from bronze (e.g., SC 59268) to yellowish-cream (e.g., QCAZ 68648).

Tadpole description.

The following description is based on a tadpole of series QCAZ 68651 in Stage 25 ( Gosner 1960). The specimen was collected in a slow-moving pool along the margins of a stream (Figure 9; 3.5187S, 78.3919W; 1991 m) at the type locality on 7 July 2017. All measurements are in mm. Total length 86.7; body length 29.1 (33.6% of total length). Body ovoid and depressed; width at the level of spiracle 19.2, height at same position 14.7; head width at level of the eyes 17.9; anterior margin of snout uniformly rounded in dorsal view and sloping at level of nares in lateral view; lateral-line system evident with supraorbital, infraorbital, mandibular, angular, postorbital, dorsal body, and ventral body lines. The arrangement of the lateral-line system is symmetrical; the supra and infra orbital lines begin at the tip of the snout and join behind the eye, continuing as a single longitudinal line extending along the anterior half of the tail. The dorsal lines extend along the posterior half of the dorsum until reaching the anterior edge of the tail, at the base of the upper fin. The angular line starts behind the orbit and extends longitudinally, contouring the spiracle, to the posterior end of the body, down towards the venter and ending at the base of the vent tube. The postorbital line starts behind the intersection of the supra and infraorbital lines and continues obliquely towards the venter, joining the anteroventral line. The mandibular line originates at the lateral border of the oral disc and runs obliquely until joining the anteroventral line. The posteroventral line forms a V whose vertex is directed towards the midposterior venter ending at the lateral edge of the venter, at the base of the spiracle. The nostrils are ovoid, not protruding and directed anterolaterally, 6.8 from tip of snout; internarial distance 8.6. Eyes positioned and directed dorsolaterally; eye length 2.8, eye width 2.5; interorbital distance 9.9. Spiracle sinistral, located at midbody and oriented posterodorsally, inner wall free from body; tube length 2.8, tube width 2.6; spiracular opening directed posterodorsally, diameter 1.6; distance from tip of snout to spiracular opening 22.5. Vent tube medial, opening directed posteriorly; tube length 3.8, tube width 2.6. Tail length 57.5; caudal musculature robust, narrowing gradually until tail terminus. At tail-body junction, tail muscle width 9.6, tail muscle height 11.7; maximum height of tail 17.7. Oral disc located anteroventrally; transverse width 11.6; bordered by two rows of small and rounded papillae; upper jaw sheath forming an arch, unpigmented, transverse width including lateral processes 4.0 (34.4% of transverse width of oral disc); oral apparatus well preserved, showing complete teeth rows. Labial tooth row formula 8(8)/11(1). Only A-8 and P-1 have gaps. Tadpoles were gregarious and fled to the bottom of the pool when disturbed.

Color in preservative of tadpoles.

In dorsal view, the body is gray, lighter on the tip of snout and towards the base of the tail, grayish cream belly, mouth cream; tail musculature grayish cream with irregular gray spots, upper and lower fins transparent, light gray with irregular dark gray spots.

Color in life of tadpoles.

In dorsal view, body brown, including head and snout; in lateral view body dark-brown. Small bronze dots concentrate in the anterior edge of the eye, become diffuse at level of the base of the spiracle. Venter cream, becoming darker medially as result of intestines being dimly visible; oral disc light brown becoming dark brown posteriorly. Iris bronze. Vent tube cream. Muscle tail light brown with gray irregular spots; lower fin transparent cream with a combination of brown and gray irregular spots; upper fin transparent light brown with light brown spots and few scattered dark gray spots. The brown coloration and the pattern of dark gray and brown spots in several individuals is maintained; however, an individual kept in captivity (QCAZ 71182) during 8 months presents an evident change in its coloration, becoming much clearer with a combination of light brown on the back and greenish brown on the flanks; muscles of tail light brown with gray spots; lower fin cream with brown spots, upper fin greenish cream becoming transparent in the distal third with dark brown spots. The differences in coloration after 8 months in captivity may be due to the effects of diet.

Tadpoles variation.

Based on a series of five individuals in stage 25 and two in stages 37 and 40. Meristic variation of tadpoles in Stages 25-40 is shown in Table 4. Seven tadpoles in Stages 25-40 varied in total length, ranging from 57.4 to 101 mm; body length ranged from 20.4 to 34.2 mm; tail length ranged from 37.0 to 67.6 mm. Inter orbital distance from 6.27 to 10.43 mm. Labial tooth row formula varied from 8(8)/11(1) to 7(7)/12(1) (Figure 10).

Etymology.

The specific name is a noun in the genitive case and is a patronym for David Hillis, an evolutionary biologist who has made significant contributions to the study of the evolution of amphibians and reptiles. During the 1980s, David Hillis carried out fieldwork in Ecuador that resulted in the discovery of three undescribed species of the H. larinopygion group. In 1990, in collaboration with WE Duellman, he published the first phylogeny for the H. larinopygion group using allozyme data ( Duellman and Hillis 1990). Currently he is professor at the University of Texas in Austin.

Distribution and natural history.

Hyloscirtus hillisi is only known from two nearby sites (airline distance = 1.7 km) on the slopes of a flattop limestone mountain in the Río Quimi basin, Provincia Zamora Chinchipe, at elevations between 1991 and 2134 m (Figure 2). Biogeographic region is Eastern Montane Forest according to Ron et al. (2018) classification. Vegetation at the type locality (Figure 11B, C) was dominated by shrubs (1.5 m tall) with sparse trees (10-15 m tall). The ground had cushioned consistency and was covered by roots and bare soil. Mosses and ground-bromeliads were abundant. This type of ground cover is locally known as bamba. Two adults and one juvenile were found on shrubs next to small streams on the Río Cristalino basin, at an elevation of 2134 m. The tadpoles and juveniles were found in ponds on the margin of Río Cristalino, at an elevation of 1991 m (Figure 11D). Collections took place in July 2017 and April 2018. The site where the adults were collected is ~500 m from the border between Peru and Ecuador. Therefore, the occurrence of H. hillisi in Peru is almost certain.

Conservation status.

Hyloscirtus hillisi is only known from two nearby sites in Cordillera del Cóndor. Population size is unknown, but the scant evidence suggests low abundances. In 2017, at the site where the tadpoles and juveniles were found, five hours of nocturnal search by five experienced herpetologists yielded no adults. At the site where the adults were found, ten hours of nocturnal search, for two nights, by two experienced herpetologists, yielded two adults and one subadult. Habitat destruction and fragmentation is evident at a distance of 3.5 km from one of the collection sites (according to Ministerio de Ambiente del Ecuador 2013 map). Cordillera del Cóndor is threatened by large and small-scale mining which has already affected amphibian populations ( Valencia et al. 2017). Because of its small known distribution and nearby habitat destruction and mining activities, we suggest to assign H. hillisi to the Critically Endangered category under criteria B1a, b(iii), according to IUCN (2001) guidelines.