Thursday, April 25, 2019

[Herpetology • 2019] Noblella thiuni • A New (singleton) Species of Minute Terrestrial-breeding Frog (Anura, Strabomantidae) from the Montane Forest of the Amazonian Andes of Puno, Peru

Noblella thiuni 
Catenazzi​ & Ttito, 2019

We describe a new species of minute, terrestrial-breeding frog in the genus Noblella. We collected a single specimen in the leaf litter of primary montane forest (2,225 m a.s.l.) near Thiuni, in the Provice of Carabaya, Department of Puno, in the upper watershed of a tributary of the Inambari River of southern Peru, the same locality where we found the types of Psychrophrynella glauca Catenazzi & Ttito 2018. We placed the new species within Noblella on the basis of molecular data, minute size, and overall morphological resemblance with the type species N. peruviana and other species of Noblella, including having three phalanges on finger IV (as in N. coloma, N. heyeri, N. lynchi, N. madreselva, N. peruviana, and N. pygmaea), and terminal phalanges T-shaped and pointed. Noblella thiuni sp. n. is distinguished from all other species of Noblella by having ventral surfaces of legs bright red, and chest and belly copper reddish with a profusion of silvery spots. The new species further differs from known Peruvian species of Noblella by the combination of the following characters: tympanic membrane absent, eyelids lacking tubercles, dorsal skin finely shagreen, tarsal tubercles or folds absent, three phalanges on Finger IV, tips of digits not expanded, no circumferential grooves on digits, inguinal spots present. The new species has a snout–vent length of 11.0 mm in one adult or subadult male. Our new finding confirms the high levels of endemism and beta diversity of small, terrestrial-breeding frogs inhabiting the moss layers and leaf litter in the montane forests of the Amazonian slopes of the Andes and adjacent moist puna grasslands, and suggests much work remains to be done to properly document this diversity.

Figure 4: Photographs of live and preserved specimen of the holotype of Noblella thiuni sp. n.
Live (A, C, E) and preserved (B, D, F) holotype of Noblella thiuni sp. n., male CORBIDI 18723 (SVL 11.0 mm) in dorsolateral (A, B), dorsal (C, D) and ventral (E, F) views. Photographs by A Catenazzi.

Noblella thiuni sp. n. 

Noblella thiuni is most similar to N. peruviana but differs from this and other known species in the genus (Catenazzi, Uscapi & von May, 2015) by having ventral surfaces of legs bright red, and chest and belly copper reddish with a profusion of silvery spots (Fig. 4). Noblella thiuni has three phalanges on Finger IV and differs from N. carrascoicola, N. lochites, N. myrmecoides, and N. ritarasquinae which have two phalanges on Finger IV (De la Riva & Köhler, 1998; Duellman & Lehr, 2009; Guayasamin & Teran-Valdez, 2009; Harvey et al., 2013; Köhler, 2000). It further differs from N. myrmecoides in having tips of toes not expanded (slightly expanded in N. duellmani, N. heyeri, and N. lynchi, tips of toes teardrop-shaped in N. myrmecoides) and in lacking circumferential grooves (present in N. myrmecoides). Among the eight species with three phalanges on Finger IV, it differs from N. heyeri, N. lynchi and N. pygmaea by lacking a distinct tympanic membrane, and from N. coloma, N. duellmani, N. madreselva and N. personina by having a tarsal fold. It further differs from N. madreselva by lacking a large white mark on venter, from N. duellmani, N. personina, and N. pygmaea by having inguinal spots, from all species but N. coloma, N. lochites, N. myrmecoides and N. peruviana in having a finely shagreen dorsum, and from all species but N. heyeri, N. lynchi, N. myrmecoides and N. peruviana by lacking tubercles on eyelids. Finally, N. thiuni differs from N. peruviana by having a smaller inner metatarsal tubercle, about the same size as outer metatarsal tubercle (inner tubercle large, about twice the size of outer metatarsal tubercle), Toe V about the same length of Toe III (Toe V shorter than Toe III).

Figure 2: Species of Noblella (Anura, Strabomantidae) from southern Peru.
(A) N. madreselva (unvouchered female, SVL 18.9 mm) from Madre Selva, La Convención, Cusco; (B) Noblella sp. “SP” (male AC 95.09, SVL 13.1 mm) from San Pedro, Paucartambo, Cusco; (C) N. pygmaea from Wayqecha, Paucartambo, Cusco (female holotype, MUSM 26320, SVL 12.4 mm); (D) Noblella thiuni sp. n. from Thiuni, Carabaya, Puno (male holotype, CORBIDI 18723, SVL 11.0 mm). Photographs by A Catenazzi.


Etymology. The name of the new species refers to the type locality and only known locality in Thiuni, Department of Puno, Peru.

Distribution, natural history and threats. The cloud forest at the type locality covers a ridge that separates two creeks and is accessible through a power line maintenance trail. We found N. thiuni in the leaf litter along with four specimens of Psychrophrynella glauca, and other frog species (Gastrotheca testudinea, Pristimantis platydactylus, and an unnamed Pristimantis sp.) in the understory vegetation or within bromeliads (Catenazzi & Ttito, 2018). Although much of the Ollachea Valley has been deforested, some relictual forests remain on steep slopes and ridges, and may support more populations of these frogs and of other unreported amphibians. In absence of more details concerning the distribution and population abundance of N. thiuni, and despite the known threats of deforestation, agriculture and hydropower development in the region (Catenazzi, Lehr & Vredenburg, 2014; Catenazzi & von May, 2014), we suggest an IUCN Red List threat assessment category of Data Deficient (IUCN, 2013). We recommend to include distribution and population surveys for this species, and the sympatric Psychrophrynella glauca, in any environmental assessment associated with hydroelectric development, power line maintenance, road construction, and similar large scale projects affecting the upper Ollachea Valley.

We describe a new species of terrestrial-breeding frog in the genus Noblella. We justify generic placement based on morphological similarity and phylogenetic analyses, but we note that such placement is tentative in light of the lack of known synapomorphies distinguishing Noblella from similar genera, particularly Psychrophrynella, and the absence of DNA sequence data for the type species of both Noblella and Psychrophrynella. We discuss limitations for singleton descriptions and adopt recent recommendations justifying our decision to proceed with a formal taxonomic decision for the new species. Our work contributes to documenting the rich diversity of small terrestrial-breeding frogs found at high elevations in the eastern slopes of the Andes of southern Peru and Bolivia.

Alessandro Catenazzi​ and Alex Ttito. 2019. Noblella thiuni sp. n., A New (singleton) Species of Minute Terrestrial-breeding Frog (Amphibia, Anura, Strabomantidae) from the Montane Forest of the Amazonian Andes of Puno, Peru. PeerJ. 7:e6780.  DOI: 10.7717/peerj.6780