Monday, June 22, 2020

[Herpetology • 2020] Dendropsophus bilobatus • A New Species of Dendropsophus (Anura, Hylidae) from southwestern Amazonia with A Green Bilobate Vocal Sac

Dendropsophus bilobatus 
Ferrão, Moravec, Hanken & Lima, 2020

Photographs: Albertina Pimentel Lima.

Recent studies have shown that species diversity of the South American frog genus Dendropsophus is significantly underestimated, especially in Amazonia. Herein, through integrative taxonomy a new species of Dendropsophus from the east bank of the upper Madeira River, Brazil is described. Based on molecular phylogenetic and morphological analyses, the new species is referred to the D. microcephalus species group, where it is differentiated from its congeners mainly by having a green bilobate vocal sac and an advertisement call comprising 1–4 monophasic notes emitted with a dominant frequency of 8,979–9,606 Hz. Based on intensive sampling conducted in the study area over the last ten years, the new species is restricted to the east bank of the upper Madeira River, although its geographic range is expected to include Bolivian forests close to the type locality.

Keywords: Amphibia, advertisement call, Amazonian biodiversity, Dendropsophus microcephalus species group, Dendropsophus bilobatus sp. nov., integrative taxonomy, morphology, upper Madeira River

Figure 4. Dendropsophus bilobatus sp. nov. from the Jaci-Parana River, a tributary of the east bank of the upper Madeira River, municipality of Porto Velho, Rondônia, Brazil, in life.
 A, B Holotype, INPA-H 41300, SVL = 18.8 mm, Jaci-Novo sampling site. C–E Adult male, INPA-H 41303, SVL = 19.9 mm, Jaci-Novo sampling site. F Adult male, INPA-H 41301, SVL = 18.9 mm, Jaci-Direito sampling site. Note the inflated translucent greenish bilobate vocal sac (A, C, D).
Photographs: Albertina Pimentel Lima.

Dendropsophus bilobatus sp. nov.

Diagnosis: A species of the Dendropsophus microcephalus species group, distinguished from other species of Dendropsophus by the following combination of characters: (1) small size, SVL 18.8–20.8 mm (N = 8) in males (females unknown), head slightly wider than body; (2) snout short, truncate in dorsal and lateral views; (3) tympanum evident, round, about one third of eye diameter, tympanic annulus distinct anteriorly, ventrally and partly posteriorly; supratympanic fold barely evident; (4) dentigerous processes of vomers small, barely prominent, and separated medially between posterior halves of choanae; (5) skin on dorsal surfaces smooth; (6) tarsal fold and tubercles on outer edge of tarsus absent; ulnar folds and tubercles absent; (7) axillary membrane extensively developed; (8) fingers about half webbed; toes about three-fourths webbed; (9) bifid distal subarticular tubercle under fourth finger; (10) pectoral glands absent; (11) generally darker coloration of the loreal-tympanic region contrasts sharply with the lighter dorsal head coloration, one or two white spots below the eye; (12) in life, ground coloration of dorsum light brown; head greenish brown laterally; flanks ventrally and posteriorly a translucent pinkish white without chromatophores; hidden surfaces of thighs yellow without melanophores; (13) in life, throat green in males; belly yellowish-white in pectoral and central parts, translucent pinkish-white in posterior and lateral parts; ventral surfaces of thighs translucent pinkish white; (14) in life, iris pale to dark brown with barely visible tiny brown veins, iris periphery dark brown to black; bones white; (15) advertisement call consisting of 1–4 notes (usually 1–2 notes), emitted regularly in series of 7–35 calls; high-pitched, monophasic, pulsed notes (3–8 pulses) with a duration of 12–24 ms and a dominant frequency of 8,979–9,606 Hz.

Distribution and natural history: 
Our research team has sampled frogs at more than 150 permanent sampling sites distributed on both banks of the upper Madeira River and along the Purus-Madeira Interfluve. Yet, we have only observed Dendropsophus bilobatus in the lowland ombrophilous open forest on the east bank of the upper Madeira River. This area is close to the border between Brazil and Bolivia, and we expect that the new species also occurs in Bolivian lowland ombrophilous open forest, as do other anuran species that are known exclusively from the east bank of the upper Madeira River (e.g., Hydrolaetare caparu [Jansen, Gonzales-Álvarez & Köhler, 2007] and Hamptophryne alios [Wild, 1995]; Simões et al. 2011, Ferrão et al. 2014).

To date, specimens of Dendropsophus bilobatus have been observed only in the rainy season (early November to late March), which coincides with the species’ breeding season. Calling males were observed in flooded areas connected to rivers of moderate (Jaci-Parana River) to large size (Madeira River). Males typically call in a large chorus while perched on leaves and tiny trunks that range in height from just a few centimeters above the water surface to ~ 2 m high. Males start calling in the crepuscule (~ 18:00 hs) and call activity has been observed at least to approximately midnight. When call activity ends remains unknown. Amplexus has not been observed. Other sympatric frogs include Rhaebo guttatus (Schneider, 1799), Boana cinerascens (Spix, 1824), B. lanciformis (Cope, 1871), Scinax sp. 6 (sensu Ferrão et al. 2016) and an uncollected Scinax with an advertisement call that resembles that of S. garbei (Miranda-Ribeiro, 1926).

Etymology: The specific name bilobatus is derived from the Latin noun bilobate. The name refers to the characteristic bilobate shape of the vocal sac of males of the new species.

 Miquéias Ferrão, Jiří Moravec, James Hanken and Albertina Pimentel Lima. 2020. A New Species of Dendropsophus (Anura, Hylidae) from southwestern Amazonia with A Green Bilobate Vocal Sac. ZooKeys. 942: 77-104. DOI: 10.3897/zookeys.942.51864