Pristimantis gralarias, Guayasamin & Arteaga & Hutter, 2018

Guayasamin, Juan M., Arteaga, Alejandro & Hutter, Carl R., 2018, A new (singleton) rainfrog of the Pristimantis myersi Group (Amphibia: Craugastoridae) from the northern Andes of Ecuador, Zootaxa 4527 (3), pp. 323-334 : 325-328

Pristimantis gralarias sp. nov. Guayasamin, Arteaga & Hutter

Holotype: MZUTI 1466 ( Figs. 1–3 ), adult female from TKA trail (0.0275° S, 78.70477° W; 2192 m), Reserva Las Gralarias , Pichincha province, Ecuador, collected on February 29 th, 2012, by Italo Tapia and Henry Imba. Genbank accession numbers: MH 306193 , MH 306194 .

Diagnosis: Pristimantis gralarias is characterized by the following combination of characters: (1) skin on dorsum and flanks shagreen with numerous, scattered, low tubercles; venter areolate; discoidal fold absent; (2) tympanic membrane and tympanic annulus evident; (3) snout short, rounded in dorsal and lateral profiles; (4) upper eyelid with several low tubercles; (5) dentigerous process of the vomer present, bearing teeth; (6) male sexual traits (e.g., vocal slits, nuptial pads) unknown; (7) first finger shorter than second; (8) fingers with narrow lateral fringes; (9) low ulnar tubercles present; (10) heel and tarsus with small, non-conical tubercles; (11) inner metatarsal tubercle conspicuous, oval, 4– 5x round outer metatarsal tubercle; (12) toes bearing narrow lateral fringes, webbing absent, discs not expanded laterally, fifth toe about same length as third; (13) in life, dorsum grayish brown, with black marks, flanks pale brown with an olive blotch and black marks, venter black with minute white spots, iris black with minute golden and silver spots; and (14) SVL in adult female 21.0 mm (n = 1), males unknown.

Comparison with similar species: Pristimantis gralarias sp. nov. is most similar to species placed in the phenetic Pristimantis myersi Group, which was initially defined by Lynch (1981) as the Eleutherodactylus myersi assembly. The new species shares the following diagnostic traits of the myersi Group (as defined by Hedges et al. 2008): small body size (females less than 28 mm), short snout, robust body, Finger I shorter than II, Toe V slightly longer than Toe III and does not extend to the proximal edge of the distal subarticular tubercle of Toe IV, digital discs narrow and rounded, tympanic membrane differentiated, cranial crests absent. Below we provide a comparison with species that form part of the P. myersi Group and that are found on the Pacific versant of the Andes; these species are: P. floridus ( Lynch & Duellman 1997) , P. hectus Lynch & Burrowes 1990 , P. leoni Lynch 1976 , P. lucidosignatus Rödder & Schimtz 2009 , P. munozi Rojas-Runjaic, Delgado, Guayasamin 2014 , P. mutabilis Guayasamin 2015 , P. onorei Rödder & Schimtz 2009 , P. pyrrhomerus Lynch 1976 , and P. sirnigeli Yánez-Muñoz, Meza-Ramos, Cisneros-Heredia & Reyes 2011 . The most conspicuous trait that distinguishes Pristimantis gralarias sp. nov. from other species in the P. myersi Group is that the new species has fingers and toes that are slender and lack a distal lateral expansion; all the other species mentioned above (except P. sirnigeli ) have some degree of distal lateral expansion ( Figs. 2 , 3 ). Pristimantis gralarias sp. nov. is further differentiated from P. hectus , P. leoni , P. lucidosignatus , P. munozi , P. mutabilis , P. onorei , P. pyrrhomerus , and P. sirnigeli by lacking a conical tubercle on the upper eyelid ( Fig. 4 ). Furthermore, the closest uncorrected pair-wise genetic distance to P. gralarias is 6.5–6.7% from P. myersi and P. ocreatus . An unpublished thesis focusing on the Pristimantis myersi Group ( Rojas-Runjaic 2012), which includes several other species of the myersi group (i.e., P. gralarias sp nov, P. hectus , P. leoni , P. sirnigeli ) also supports the lineage differentiation between P. gralarias sp nov and all other sampled Pristimantis .

Description of holotype ( Figs. 1–3 ): Adult female, with relatively robust body ( Fig. 1 ). Skin of dorsum and flanks shagreen, with numerous scattered low tubercles; skin on venter areolate. Head slightly longer than wide (Head Length = 37% of SVL; Head Width = 35% of SVL). Snout rounded in dorsal and lateral views, with very small papilla at tip; canthus rostralis distinct, slightly concave; lips rounded, not flared. Black canthal stripe present. Nostrils slightly protuberant, directed laterally. Internarial region and top of head flat. Eye of moderate size, its diameter 13% of SVL. Tympanic membrane differentiated, but pigmented as surrounding skin; tympanum conspicuous, oval, diameter 5.7% of SVL. Supratympanic fold low, obscuring upper margin of tympanum; black supratympanic stripe present. Dentigerous processes of vomers conspicuous, having triangular shape, wellseparated from each other; each process bears 3 (right) and 4 (left) teeth. Choanae of moderate size, elliptical, not concealed by palatal shelf of maxillary arch. Tongue large, cordiform, with its anterior third attached to the floor of mouth. Forearm with three low ulnar tubercles. Fingers slender; discs not expanded laterally, and with clearly defined circumferential groove; disc on Finger III narrower than tympanum diameter. Relative lengths of fingers I <II <IV <III. Fingers with narrow dermal fringes; webbing absent. Subarticular tubercles round, simple, moderate-sized. Supernumerary tubercles present, numerous, fleshy and small. Palmar tubercle well-differentiated, bifid distally. Inner metacarpal tubercle large, elliptical.

Hind limbs moderately robust; tibia length 49% SVL; foot length 47% SVL. Heel with small, non-conical tubercle; four low, non-conical tarsal tubercles present. Inner metatarsal tubercle ovoid, 4–5 times size of round outer metatarsal tubercle; planar surface with numerous small supernumerary tubercles; subarticular tubercles single, round, moderate-sized. Toes with narrow lateral fringes; toe discs not expanded laterally; pads with clearly defined circumferential groove. Relative length of toes I <II <III = V <IV; toe webbing absent.

Color in life: Dorsum grayish brown, with black marks; flanks pale brown with an olive blotch and black marks; dark red groin. Lip with black stripes; black canthal and supratympanic stripes. Venter black with minute white spots; iris black with minute golden and silver spots and orange circunpupillary ring ( Fig. 1 ).

Color in preservative: Dorsum and flanks grayish brown, with black marks; cream groin. Black canthal and supratympanic stripes. Venter dark brown, with minute cream spots.

Measurements of the holotype (in mm): MZUTI 1466, adult female. SVL 21.0; Femur length 9.6; Tibia length 10.3; Foot length 9.8; Head length 7.7; Head width 7.4; Snout-to-eye distance 1.7; Tympanum 1.2; Radioulna length 5.1; Hand length 5.4; Eye diameter 2.7; Interorbital distance 2.0; Finger I length 3.5; Finger II length 3.9; Finger III Disc Diameter 0.4; Toe IV length 9.9; Toe V length 6.4; Toe IV Disc Diameter 0.4.

Distribution: Pristimantis gralarias is only known from its type locality, Reserva Las Gralarias (0.0275° S, 78.70477° W; 2192 m; Fig. 5 ), Pichincha Province, Ecuador.

Natural History: During the night, the holotype was found on a leaf 90 cm above ground in a primary forest.

Conservation: Pristimantis gralarias is only known from its type locality, Reserva Las Gralarias ( Fig. 1 ), Pichincha Province, Ecuador. Given that the cloud forests of northwestern Ecuador are relatively well-known in terms of Pristimantis diversity (see Lynch & Duellman, 1997; Arteaga et al. 2013) and that the new species is extremely rare at its type locality—despite intensive fieldwork ( Guayasamin et al. 2014, 2015; Hutter & Guayasamin 2015)—we consider Pristimantis gralarias as Critically Endangered, following IUCN (2001) criteria B2a (known to exist from a single locality) and B2biii (continuing decline, observed, inferred or projected, in area, extent and/or quality of habitat; see Palacios-González et al. 2015).

Etymology: The specific epithet gralarias is a noun in apposition and refers to the type locality of the new species, Reserva Las Gralarias (http://www.reservalasgralarias.com). We take pleasure in dedicating this species to the reserve and the team of people, led by Dr. Jane Lyons, for efforts on the conservation and research of Ecuadorian cloud forests. As the English common name for this species, we suggest Gralarias Rainfrog. As the common name in Spanish, we suggest Cutín de Las Gralarias.

Evolutionary relationships: Phylogenetic inference shows that Pristimantis gralarias sp. nov. is part of a clade composed, mostly, by species from the P. myersi Group ( Fig. 6 ). Specific relationships vary depending on the inference method; the Maximum Likelihood tree shows P. gralarias as sister to a clade formed by P. festae , P. leoni , P. ocreatus , P. myersi ( Fig. 6 ). In contrast, the Bayesian tree infers a sister relationship between P. gralarias and a clade composed by P. ocreatus and P. myersi . These topological discrepancies are expected giving that clade support at this level is low ( Fig. 6 ). The sample herein labelled as P. myersi (WED 53004/KU 202419) has been misidentified in previous studies as P. thymelensis (see Zhang et al. 2013; Padial et al. 2014; González-Durán et al. 2017; Rivera-Correa et al. 2017).

Figures

FIGURE 1. Pristimantis gralarias sp. nov. in life, holotype, MZUTI 1466.

FIGURE 2. Hands of species in the Pristimantis myersi Group, showing differences in distal lateral expansion of fingers (absent in P. gralarias). Illustrated specimens: P. gralarias sp. nov. (MZUTI 1466), P. leoni (KU 130870, from Lynch 1976), P. pyrrhomerus (KU 131610, from Lynch 1976), P. floridus (USNM 239674, form Lynch & Duellman 1997). Not drawn to scale.

FIGURE 3. Plantar view of feet showing differences in distal lateral expansion of toes. (A) Pristimantis gralarias sp. nov. (MZUTI 1466), and (B) P. hectus (IND-AN 1941, from Lynch & Burrowes 1990). Not drawn to scale.

FIGURE 4. Species in the Pristimantis myersi Group. (A) P. gralarias sp nov., Reserva Las Gralarias, 2192 m, Pichincha province, MZUTI 1466. (B) P. hectus, Reserva Integral Otonga, 2110 m, Cotopaxi province, MZUTI 2062. (C) P. floridus, Pichincha province, photo by Luis A. Coloma. (D) P. sirnigeli, 2825 m, Reserva Siempre Verde, Imbabura Province, MZUTI 3159. (E) P. pyrrhomerus, Pilaló, 2720 m, Cotopaxi province. Photographs not at scale.

FIGURE 5. Known distribution of Pristimantis gralarias sp. nov.

FIGURE 6. Phylogeny of Pristimantis trimmed to show only the most closely related species to P. gralarias sp. nov. The full phylogeny is available from Guayasamin et al. (2007). Support values are presented as bootstraps and posterior probabilities. GenBank accession numbers are in parentheses. *Sample (WED 53004/KU 202419) previously identified as P. thymelensis, but that actually corresponds to P. myersi.