Tuesday, February 8, 2022

[Herpetology • 2022] Diasporus lynchi • A New Golden Species of Diasporus (Anura: Eleutherodactylidae) from southwestern Colombia, with Evaluation of the Phylogenetic Significance of Morphological Characters in Diasporus

Diasporus lynchi
 Ospina Sarria​, Velásquez Trujillo, Castaño Saavedra, Castillo & Bolívar-García, 2022

 Anchicaya’s Golden Frog | Rana Dorada de Anchicayá  ||  FrogDOI: 10.7717/peerj.12765
Photos: J.J. Ospina-Sarria.

A new species of Diasporus is described from the lowlands of southwestern Colombia. The new species exhibits a yellowish coloration in life, a character that it shares with other three species in the genus—Diasporus citrinobapheus, D. gularis, and D. tigrillo. The new species differs from all other congeners in having two chrome orange spots (=glandlike protrusions) on sacral region, smooth ventral skin, basal webbing between the toes, and distal papillae at tips of disc covers on fingers II–IV and toes II–IV. Further, the new species differs from all congeners by an uncorrected p-distance of > 5.56% of the 16S rRNA gene fragment examined. In addition to the new species described herein, we demonstrated that the possession of a yellowish coloration in life optimizes unambiguously as a synapomorphy of a clade within Diasporus, which may be recognized as the Diasporus diastema species group. We also discussed the phylogenetic significance of two morphological characters previously considered of systematic value in Diasporus, the occurrence of oval palmar tubercles (undivided) and longitudinal folds (of the vocal sacs) on the throat. On this basis, we demonstrated that these characters appear to be symplesiomorphies rather than synapomorphies of Diasporus. Regarding pointed disc covers (ungual flap) present in some species of Diasporus, we show that this character conflates various characters, involving variation in pad shape, dorsal outline of the disc (ungual flap), and dependence between discs of different digits. Finally, considering that phenotypic data are a valuable source of evidence in testing phylogenetic hypotheses of terraranan frogs, we encourage future research to incorporate phenotypic evidence into phylogenetic studies involved in the genus Diasporus.

Living specimens of the Diasporus species known from Colombia.
Diasporus lynchi (A–B; holotype, CPZ-UV 7298 (field no. JJS 065), adult male, snout–vent length [SVL] 19.1 mm; photo: J.J Ospina-Sarria);
Diasporus gularis (C; not collected, Pianguita, Valle del Cauca; J.J Ospina-Sarria);
Diasporus quidditus (D; holotype, ICN 45173, adult male; photo: J.D. Lynch);
Diasporus anthrax (E; MHUAA 09775, San Vicente de Chucuri, Santander; photo: H. Martinez);
Diasporus tinker (F; holotype, ICN 45174, adult male; photo: J.D. Lynch).

Dorsal and ventral views of Diasporus lynchi (holotype, CPZ-UV 7298 (field no. JJS 065) in life.
Photos: J.J. Ospina-Sarria.

Diasporus lynchi sp. nov. 
Proposed standard Spanish name. Rana Dorada de Anchicayá
Proposed standard English name. Anchicaya’s Golden Frog

Diagnosis.—Diasporus lynchi is diagnosed by the following combination of characters: (1) skin on dorsum and venter smooth; discoidal fold absent; dorsolateral folds absent; (2) tympanic membrane absent; tympanum annulus visible through skin round, its length 33–40% of eye length in two males; supratympanic fold poorly defined; (3) snout subacuminate in dorsal view, truncate in profile; canthus rostralis angular, weakly concave; loreal region slightly concave; (4) upper eyelid bearing two or three small tubercles; narrower than IOD (54.1–60% IOD); cranial crest absent; (5) choanae small, ovoid; partially concealed by palatal shelf of maxillary arch; dentigerous processes of vomers prominent and positioned posterior to level of choanae, triangular in outline, separated medially by a distance equal to the width of the visible dentigerous process, each dentigerous process of vomers bearing four to six teeth; (6) males having vocal slits and large subgular vocal sac (forming longitudinal folds, Figs. 3B, 3D); nuptial pads absent; testes white; (7) finger I shorter than finger II; discs slightly wider than digits, disc on finger I smaller than that of finger II and this in turn smaller than discs on fingers III and IV; disc cover on finger I unornamented; papillae on digits II, III, and IV; triangular pads on fingers; (8) fingers with lateral fringes; palmar tubercle oval (undivided; Fig. 4A); thenar tubercle oval, equal in size to palmar tubercle; supernumerary tubercles low, restricted to the proximal segments of fingers III and IV; subarticular tubercles low, with rounded base and larger than supernumerary tubercles; (9) ulnar tubercles absent; (10) heel and tarsus lacking tubercles and folds; (11) oval inner metatarsal tubercle, its length four times its width; low, conical outer metatarsal tubercle one-fourth size of inner metatarsal tubercle; supernumerary plantar tubercles absent; subarticular present; (12) toes bearing lateral fringes; webbing basal, I 2−- 2+ II 2−- 3+ III 3−- 4+IV 4−- 21/2 V (Fig. 4B); toe III shorter than toe V; toe III reaching midway between penultimate and distal subarticular tubercle of toe IV; toe V extending to distal edge of distal subarticular tubercle of toe IV; discs of toes III–V larger than disc of toe II and this in turn larger than discs on toe I; discs covers on toe I and V unornamented; discs with minute papillae at tips of toes II, III, and IV; triangular pads on toes; (13) in life, dorsal ground color yellow with dark markings, anterior and posterior surfaces of thighs chrome orange. Two chrome orange spots (=glandlike protrusions) on sacral region (Fig. 3A). Canthal, interorbital, and postocular stripes are poorly defined. Limbs with darks marking and disc covers blackish gray (Fig. 2A). Ventral surfaces of body almost transparent with scattered iridophores, ventral surfaces of hind limbs chrome orange, and vocal sac yellow with diminutive black spots (Fig. 3B). The iris is golden-bronze with a reddish-brown horizontal streak; (14) SVL in three adult males 19.1, 19.5, and 19.7 mm.

Distribution and ecology.—The holotype was found vocalizing in leaf litter along a forested stream in a primary forest at night. The calls sound like a “whistle”. The paratypes were also found along stream in primary but thinned forest. Both paratypes were found at distances no greater than 2 m from the stream. Thus, the species seems to be associated with streams in primary forests. As in other species of Diasporus (e.g., D. gularis and D. tinker), D. lynchi vocalizes from concealed sites (e.g., dried leaf); therefore, a considerable effort is required to detect each individual. The species occurs at low elevations in the humid tropical regime (54–300 m elevation) in localities in the vicinity to the Estación Agroforestal Bajo Calima, Departamento de Valle del Cauca, Colombia (Fig. 5), which is the locality type of Diasporus quidditus and D. tinker.

Etymology.—The specific name is an noun in the genitive case and is a patronym for John D. Lynch, who first found the species during his explorations of the Bajo Calima, and in recognition of his many contributions to understanding the taxonomy and systematics of the world’s most diverse family-group of amphibians (superfamily Brachycephaloidea = Terraranae).

With the description of Diasporus lynchi, 17 species compose the genus Diasporus. Phylogenetic analyses based on molecular evidence indicate that D. lynchi is the sister species of a clade containing D. gularis, D. aff. diastema EPL, D. aff. diastema MM, D. tigrillo, D. diastema, and D. citrinobapheus. Furthermore, we found that the possession of a yellowish coloration in life optimizes unambiguously as a morphological synapomorphy for this clade. Although species of genus Diasporus are characterized by having oval palmar tubercles (undivided) and longitudinal folds (of the vocal sacs) on the throat, none of them optimizes unambiguously as synapomorphies of this genus. Another morphological character that has been suggested to characterize the species of Diasporus is the pointed disc covers (ungual flap), however, there is evidence revealing that multiple characters have been conflated under this character.

Frogs of the genus Diasporus, together with the genus Pristimantis, are among the terraranan genera with the greatest taxonomy uncertainty for many of their taxa. This is because, as mentioned earlier, no attempt at morphological revision has been conducted recently. In the specific case of Diasporus, this situation has led to a lack of confidence in the taxonomic identification of numerous DNA sequences deposited in GenBank (e.g., Diasporus diastema, D. hylaeformis, D. quidditus, D. tinker). To address this situation, it is necessary a taxonomic revision incorporating morphological evidence. Besides, and considering that many species of Diasporus are sympatric and syntopic, we recommend being cautious when assigning species identification based on specimens collected near or at the type locality. For example, the Estación Agroforestal Bajo Calima in the Departamento de Valle del Cauca, Colombia is the type locality of Diasporus quidditus and D. tinker, but D. gularis and D. lynchi can also be found. That is, at the Estación Agroforestal Bajo Calima is possible to find four of the five species of the genus Diasporus known from Colombia, except for D. anthrax that is distributed in the Valle of the Magdalena River (Frost, 2021).

Finally, as has been pointed out in the literature, phenotypic data are a valuable source of evidence in testing phylogenetic hypotheses of terraranan frogs. Therefore, we hope our results encourage further research using phenotypic characters into phylogenetic and taxonomic studies involving the genus Diasporus.

Jhon Jairo Ospina Sarria​, David Andrés Velásquez Trujillo, Christian Oswaldo Castaño Saavedra, Luis Fernando Castillo and Wilmar Bolívar-García. 2022. A New Golden Species of Diasporus (Anura: Eleutherodactylidae) from southwestern Colombia, with Evaluation of the Phylogenetic Significance of Morphological Characters in Diasporus.  PeerJ. 10:e12765. DOI: 10.7717/peerj.12765