Thursday, September 2, 2021

[Herpetology • 2021] Allobates grillicantus • A New Nurse Frog (Anura: Aromobatidae) with a Cricket-Like Advertisement Call from Eastern Amazonia

Allobates grillicantus
 Moraes & Lima, 2021

Integrative analyses, long-term studies, and access to remote areas in Amazonia have led to new hypotheses and increased resolution of the systematics and taxonomy of the small nurse frog genus Allobates (family Aromobatidae). During anuran sampling in the Middle Tapajós River region, state of Pará, Brazil, we collected data on a new cryptically colored species of Allobates with a cricket-like advertisement call. Here, we name and describe this new species, following an integration of phenotypic, ecological, and molecular analyses. The results of a phylogenetic analysis based on mitochondrial and nuclear DNA placed the new species as the sister taxon of Allobates grillisimilis. Genetic pdistances between the two sister taxa at the 16S region of the mitochondrial DNA ranged from 7% to 9%. A sister-species relationship between the new species and A. grillisimilis is also supported by phenotypic evidence. Adults of the new species are small (snout–vent length 15.2–16.8 mm in males and 16.5–17.7 mm in females), with a dorsum uniformly tan to reddish brown, a dark brown lateral stripe and a white ventrolateral stripe, arms pale tan brown and legs greyish-brown, and venter yellowish colored, with variable extension and shades of yellow, paler on the throat. The advertisement call is a trill with a mean peak frequency of 5830.2 Hz, arranged in series of short, closely spaced, pulses (mean of 24.3 pulses/s), and followed by silent intervals of variable duration. We discuss the putative drivers generating and maintaining the distinctiveness between the new species and the allopatrically distributed sister taxon, and on threats to the persistence of the new species. With this species description, the Middle Tapajós River region is consolidated as having one of the highest alpha diversities for the genus Allobates in Amazonia.

Key words: Anura; Bioacoustics; Biogeography; Brazil; Conservation; Cryptic diversity; DNA; Integrative taxonomy; Para

FIG. 5. Variation in color in life and external morphology of some adult specimens from the type series of Allobates grillicantus in dorsal, lateral, and ventral views (from left to right).
 (A) MPEG 43038, male, 15.7 mm snout-vent length (SVL);
(B) INPA-H 41352, male, 15.8 mm SVL;
(C) MPEG 43042, female, 17.7 mm SVL;
(D) MPEG 43043, female, 17.7 mm SVL.
 Not to scale. Photographs by A.P. Lima.

Allobates grillicantus sp. nov.

Etymology.— The specific epithet grillicantus means ‘‘cricket song’’ and refers to the cricket-like advertisement call emitted by this species. It is a compound Latin noun in the nominative case used in apposition, derived from gryllus ,meaning ‘‘cricket’’ and cantus, meaning ‘‘song.’’ The name is purposely similar to the sister taxon A. grillisimilis to refer to common ancestry.

FIG. 1. Bayesian phylogenetic tree of Allobates inferred from a concatenated data set of eight genes (four mitochondrial and four nuclear), highlighting the position of the new species from the Middle Tapajós River region, state of Pará, Brazil as the sister taxon of Allobates grillisimilis. Outgroups were omitted, and the informal clade names to right of the tree follow the subdivision of Réjaud et al. (2020). Support values are shown above branches: asterisks represent posterior probability 1.00-0.99, black circles 0.98-0.95, open circles 0.94-0.85, and support below this level were omitted. (H) Holotype; (T) Tadpole. Photographs by A.P. Lima.  

FIG. 9. Geographic distribution of  Allobates grillicantus (squares) and its sister taxon Allobates grillisimilis (dots) relative to the lower-middle courses of the Madeira River and the Tapajós River. Inset (lower left) shows the area within South America and Brazil. Dotted symbols indicate species' type localities.  

Leandro J.C.L. Moraes and Albertina P. Lima. 2021. A New Nurse Frog (Allobates, Aromobatidae) with a Cricket-Like Advertisement Call from Eastern Amazonia. Herpetologica. 77(2); 146-163. DOI: 10.1655/Herpetologica-D-20-00010.1