Pristimantis similaris, Herrera-Alva & Catenazzi & Aguilar-Puntriano, 2023

Herrera-Alva, Valia, Catenazzi, Alessandro & Aguilar-Puntriano, Cesar, 2023, A new cryptic species of terrestrial breeding frog of the Pristimantis danae Group (Anura, Strabomantidae) from montane forests in Ayacucho, Peru, ZooKeys 1187, pp. 1-29 : 1

Pristimantis similaris sp. nov.

Figs 4 , 5 , 6

Common name.

English: Similar Rubber Frog. Spanish: Rana cutín similar.

Generic placement.

We assign this species to the genus Pristimantis , based on morphology and molecular data (Figs 2 , 4 , 6 ).

Type material.

Holotype. MUSM 41030, adult male (Figs 4 , 5 ) from Comunidad Cajadela (12°57'16.50"S, 73°35'0.70 ”’ W, 1460 m a.s.l.), Distrito Anco, Provincia La Mar, Departamento Ayacucho, Peru, collected on 15 November 2018 by V. Herrera-Alva, E. Castillo-Urbina, V. Díaz, M. Fernandez, and J. Gamboa.

Paratypes. Nine specimens. Five adult females (MUSM 41031, 41032, 41035, 41036 and MUSM 41037). Four adult males (MUSM 41029, 41028, 41033 and MUSM 41034). All the specimens were collected at the type locality, except MUSM 41037, which was collected in Comunidad Machente (12°41'31.70"S, 73°51'0.30"W, 1640 m a.s.l.), Distrito Ayna, Provincia La Mar, Departamento Ayacucho, Peru, on 11 November 2021 by V. Herrera-Alva, E. Castillo-Urbina, V. Díaz and K. Ñaccha.

Diagnosis.

A new species of Pristimantis assigned to the P. danae species Group having the following combination of characters: (1) Skin on dorsum shagreen, skin on venter areolate; discoidal and dorsolateral folds present, weak; thoracic fold present; (2) tympanic membrane and tympanic annulus present, distinct, visible externally; (3) snout subaccuminated in dorsal view, round in lateral view; (4) upper eyelid lacking tubercles; EW smaller than IOD; cranial crest absent; two small and flat tubercles above the snout near the eyes; (5) dentigerous processes of vomers low, oblique in five of the paratypes, absent in four paratypes and the holotype; (6) males with vocal slits, subgular vocal sac large extending on to chest and without nuptial pads; (7) Finger I slightly shorter than Finger II; discs of digits expanded, flat and truncated; (8) fingers without lateral fringes; (9) ulnar tubercles present, but diffuse; (10) heel with two to three small and flat tubercles; inner tarsal fold present, small; (11) inner metatarsal tubercle ovoid, 2-3 times larger than outer one; outer metatarsal tubercle small, ovoid; numerous and flat supernumerary tubercles; (12) toes without lateral fringes; basal toe webbing absent; toe V is slightly longer than toe III; toe discs about as large as those on fingers; (13) in life, dorsum varies from blackish to dark brown with three conspicuous chevrons (not very visible in some cases) (Fig. 6 ); in most of the adults, the anterior surfaces of thighs reddish-orange, posterior surfaces of thighs brown; flanks cream without tubercles; groin same pattern as flanks mostly, some specimens with orange-reddish colouration (Figs 4 , 6 ); venter cream to yellow with black conspicuous reticulations in the throat and black marks in the chest, males present yellow throat with black or white longitudinal reticulations not as conspicuous as in females (Figs 4 , 6 ); iris dark copper-coloured with fine black vermiculations; (14) SVL in adult females 20.8-25.2 mm (mean = 23.4 ± 1.8 SE, n = 5), in adult males 17.0-18.6 mm (mean = 18.1 mm ± 0.7 SE, n = 5).

Comparisons.

Pristimantis similaris is distinguished from its congeners in Peru and Bolivia by the following combination of characters: skin on dorsum areolate, tympanum and tympanic annulus distinct, weakly-defined discoidal and dorsolateral folds, two small and flat tubercles above the snout near the eyes (not conspicuous in preservative), dorsum dark brown with three darker chevrons, anterior surface of thighs usually orange-reddish and posterior surface of thighs dark brown. Pristimantis similaris can be distinguished from P. rhabdolaemus and P. pharangobates by the following characters (characters in parenthesis): smaller SVL of 20.8-25.8 mm in ten females and 15.2-18.9 mm in eight males ( P. pharangobates 23.1-27.8 mm in females and 15.2-18.2 mm in males; P. rhabdolaemus 25.5-31.9 mm in females and 24.1-26.3 mm in males); absence of scapular tubercles (present in both species); presence of conspicuous longitudinal black and white or yellow marks on the throat and chest (less conspicuous in P. pharangobates and P. rhabdolaemus ).

Other species in the Pristimantis danae species Group that are similar to P. similaris include P. danae , P. reichlei , P. scitulus and P. toftae . Pristimantis danae and Pristimantis reichlei also have brown chevrons in the dorsum and differ from the new species by the combination of the following characters: males nuptial pads absent (present in P. danae and P. reichlei ), dorsolateral folds present (weak in P. danae and absent P. reichlei ), small pale spots in the posterior surfaces of the thighs absent (present in P. danae and P. reichlei ) and smaller size in P. similaris . Pristimantis scitulus is morphologically similar to P. similaris and has a parapatric distribution (Yuraccyacu, in the Piene Valley, Ayacucho Region). Pristimantis similaris can be distinguished by lacking a conical tubercle in the upper eyelid and heels (present in P. scitulus ), mid-ventral line absent (present in P. scitulus ) and absence of marks in the groin or thighs (conspicuous dark spots in the groin that is continuous as marks on the posterior surfaces of the thighs in P. scitulus ). Pristimantis toftae is a smaller species that is superficially similar to P. similaris . The new species can be distinghished by the absence of coloured marks or spots in the groin or other parts of its body (yellow spot in the groins of P. toftae ), absence of labial bar (presence of a white labial bar in P. toftae ).

Pristimantis similaris is also similar to some species in the Pristimantis conspicillatus species Group, which includes P. bipunctatus , P. skydmainos and P. iiap . The parapatric Pristimantis bipunctatus (found in Calicanto at 1940 m. a.s.l. in the Piene Valley, Ayacucho Region), has dorsum and ventral skin shagreen and areolate, snout long, upper eyelids without tubercules similar to P. similaris , but the latter differs by having finger I slightly shorter than finger II (finger I and finger II about equal length in P. bipunctatus ), discs on outer fingers truncated (broadly rounded in P. bipunctatus ), scapular tubercules absent (present in P. bipunctatus ) and by its smaller size (22.6-28.8 mm in males and 32.4-41.5 mm in females in P. bipunctatus ). P. similaris can be distinguished from P. skydmainos by the absence of a mid-dorsal tubercle (present in P. skydmainos ), absence of nuptial pads (present in P. skydmainos ), finger I smaller than finger II (finger I longer than finger II in P. skydmainos ), absence of spots or marks in the posterior surfaces of the thighs (minute cream flecks on the posterior surfaces of the thighs in P. skydmainos ) and the absence of W-shaped marks (present in the scapular region in P. skydmainos ). Pristimantis similaris differs from P. iiap from the lowland Amazon of the Ucayali Region by lacking large granules on flanks (present in P. iiap ), lacking granules on the upper eyelids (present in P. iiap ) and by having finger I shorter than finger II (finger I and II about the same length in P. iiap ).

Another species with some resemblance (mainly on the throat in ventral view) to the new species is Pristimantis tanyrhynchus . Pristimantis similaris can be distinguished from P. tanyrhynchus by the absence of nuptial pads in males (present in P. tanyrhynchus ) and absence of tubercles on the heel (heel with a conical and large tubercle in P. tanyrhynchus ).

Description of the holotype.

Head longer than wide; head length 43% of SVL; head width 35% of SVL; cranial crests absent; snout subaccuminated in dorsal view and in lateral view (Fig. 4A, B, D ); eye-nostril distance same as the eye diameter; nostrils slightly protuberant, directed dorsolaterally; canthus rostralis long, straight in lateral and in dorsal views; loreal region concave; upper eyelid without tubercles, width 90% of IOD (see photo in life Fig. 4 ); supratympanic fold short and narrow, extending from posterior margin of upper eyelid slightly curved to insertion of arm; tympanic membrane and annulus present; distinct conical postrictal tubercles present bilaterally. Choanae small, ovoid, not concealed by palatal shelf of maxilla; dentigerous processes of vomers absent; vocal slits present; tongue longer than short, oval, about a quarter times as long as wide, notched posteriorly, half of the tongue posteriorly free; one large vocal sac extending on to chest.

Skin on dorsum and flanks shagreen, continuous dorsolateral folds present extending from posterior level of tympanic area to level of hind limb insertion; skin on throat, chest and belly areolate; discoidal fold present; thoracic fold present.

Outer ulnar surface without tubercles; palmar tubercle bifid; thenar tubercle ovoid; subarticular tubercles well defined, most prominent on base of fingers, ovoid in ventral view, subconical in lateral view; supernumerary tubercles indistinct; fingers long and thin lacking lateral fringes, Finger I shorter than Finger II; tips of digits of fingers expanded, truncated, with circumferential grooves; nuptial pads absent (Fig. 5A ).

Hind limbs long, slender, tibia length 58% of SVL; foot length 49% of SVL; dorsal surfaces of hind limbs tuberculate; inner surface of thighs smooth, posterior surfaces of thighs shagreen, ventral surfaces of thighs smooth; heels each with three small conical tubercles; outer surface of tarsus with one minute low tubercle; inner tarsal fold present; inner metatarsal tubercle ovoid, two times the size of round outer metatarsal tubercle; subarticular tubercles well defined, ovoid in ventral view, subconical in lateral view; few plantar supernumerary tubercles, about one quarter the size of subarticular tubercles; toes without lateral fringes; basal webbing absent; tips of digits expanded, truncated, less expanded than those on fingers, with circumferential grooves; relative length of toes: 1 <2 <3 <5 <4; Toe V slightly longer than Toe III (tip of digit of Toe III and Toe V not reaching distal subarticular tubercle on Toe IV; Fig. 5B ).

Measurements (in mm) of the holotype.

SVL 17.0; tibia length 9.9; foot length 8.4; head length 7.3; head width 5.9; eye diameter 2.3; inter orbital distance 1.9; upper eyelid width 1.7; internarial distance 2.0; eye-nostril distance 2.3; tympanum length 1.0; tympanum height 1.1; forearm length 4.3.

Colouration of the holotype in life

(Fig. 4 ). In life, dorsum dark brown with three conspicuous chevrons; flanks cream without tubercles, groin same pattern as flanks with orange-reddish colouration; anterior surfaces of thighs reddish-orange, posterior surfaces of thighs brown; venter cream to yellow with black conspicuous reticulations in the throat and black marks in the chest; iris dark copper-coloured with fine black vermiculations (Fig. 4 ).

Colouration of the holotype in preservative.

The dorsal ground colouration is pale brown with three browner chevrons; narrow blackish canthal and supratympanic stripes; flanks pale brown with dark brown and cream flecks forming irregularly-shaped diagonal bars; groin and anterior surfaces of thighs brown with dark brown flecks; chest, belly and ventral surfaces of thighs pale cream, throat pale cream and grey-striped; palmar and plantar surfaces and fingers and toes dark brown; iris pale grey.

Variation.

All specimens have the same general appearance, with three chevrons on the dorsum. MUSM 41029 is completely yellow and lacks marks on the chest or throat. MUSM 41032 has two brown-yellowish longitudinal bars on the dorsolateral folds. MUSM 41341 is blackish-brown and the three chevrons are not very visible (Fig. 6 ). Some individuals (MUSM 41030-2, 41036-7) lack the dentigerous processes of vomers. Morphological measurements ranges and proportions of types are included in Tables 2 , 3 .

Etymology.

The specific name corresponds to the Latin word “similar”. This refers to the similarity of the new species and its close phylogenetic relationship with P. rhabdolaemus and P. pharangobates .

Distribution and natural history.

The new species is only known from montane forests of Ayna and Anco in Departamento Ayacucho at elevations from 1200-2000 m a.s.l. in secondary forests (Figs 1 , 3 ). This species was found only at night after 18:00 hours, usually perching on wet leaves 0.5-1.5 m above the ground. Males call rarely and their calls are overshadowed by other male species ( Pristimantis lacrimosus species Group) calling louder. The species is common and appears to tolerate some human disturbance, because it was found near abandoned farms, less frequented roads and in the sourroudings of abandoned houses. Syntopic species included candidate new species in the Pristimantis lacrimosus species Group and candidate new species in the Pristimantis platydactylus species Group, which were more abundant than the new species. Sympatric species included frogs and toads Gastrotheca pacchamama , Nymphargus pluvialis , Boana palaestes , Rhinella inca , Dendropsophus vraemi and Hyalinobactrachium aff. bergeri ; lizards Cercosaura manicata , Stenocercus crassicaudatus and Potamites montanicola ; and snakes Dipsas cf. peruana , Leptodeira annulata and Epictia cf. peruviana .

Figures

Figure 1. Montane forest of Cajadela (A) and Machente (B), Ayacucho Department. Type locality of Pristimantis similaris sp. nov. in Cajadela (A). Note the presence of secondary forest in both localities. Photo A taken on 8 November 2021 and B, on 24 October 2022. Arrow marks the type locality.

Figure 2. Maximum Likelihood tree of concatenated genes 16 S rRNA, COI, RAG 1 and TYR taken from GenBank and novel sequences. Numbers on nodes are bootstrap values (see Materials and Methods section for details). Green shadow corresponds to the ingroup. Pristimantis similaris sp. nov. in red, Pristimantis sp. 3 from Bolivia in purple and Pristimantis sp. from Cusco in blue. Maximum Likelihood optimal tree with bootstrap node values from the analysis of a concatenated dataset of 591 bp (16 S), 685 bp (COI), 624 bp (RAG 1) and 545 bp (TYR) of 128 species aligned by MAFFT and node support assessed using 10,000 replicates in IQTREE.

Figure 3. Distribution map of some species of the P. danae species Group in Ayacucho and Cusco Departments. Raster of altitude from 500 to 4500 m. a. s. l. (white to black). Locality of new species in red circles.

Figure 4. Pristimantis similaris sp. nov. (A-D) male. SVL: 17.0 mm. Holotype. MUSM 41030. Photos by Vladimir Diaz-Vargas.

Figure 5. Pristimantis similaris sp. nov. A hand B toe. Male. Holotype. MUSM 41030. Photos by VHA.

Figure 6. A-H colour and pattern variation of Pristimantis similaris sp. nov. Specimen from A-F collected in Cajadela: A, B male MUSM 41029 C, D female MUSM 41031 E, F female MUSM 41032. Specimen G, H male MUSM 41326 collected in Machente. Photos by V. Diaz-Vargas and E. Castillo-Urbina.