Hidden in the litter: cryptic diversity of the leaf-litter toad Rhinella castaneotica–proboscidea complex revealed through integrative taxonomy, with description of a new species from south-western Amazonia

Abstract

Recent studies have showed that several species of frogs previously thought to be widespread throughout Amazonia are species complexes with each individual species displaying smaller geographic ranges and that only a small fraction of Amazonian frogs are indeed widely distributed. Evaluating cryptic diversity within these complexes and describing associated candidate species are crucial for biological conservation, especially in regions where tropical forest is rapidly vanishing such as in southern Amazonia. In this study, we integrate mitochondrial (16S rRNA), morphological, bioacoustic and breeding behaviour data to investigate whether populations of the leaf-litter toad Rhinella castaneotica–proboscidea complex are conspecific as suggested by former studies. Our molecular analysis recovered five main clades in this complex whose geographic distributions are likely limited by geographic barriers. Morphological, bioacoustic and breeding behaviour data support the heterospecificity of three of them. The names R. proboscidea sensu stricto and R. castaneotica sensu stricto are applied to the populations from central and eastern Amazonia, respectively. The population from south-western Amazonia is described herein as a new species. It differs from other members of the R. margaritifera species group by its snout–vent length (35.7–45.2 mm in males and 38.3–52.1 mm in females), poorly developed supratympanic crests, dorsal skin smooth in males and granular in females, and advertisement call with average call duration of 285 ± 28 ms, 11 ± 1 notes, last note duration of 41 ± 10 ms and dominant frequency of 1,810 ± 220 Hz. Moreover, males of the new species vocalize while aggregated in temporary ponds unconnected to streams and do not exhibit necrophilic behaviour. South-western Amazonia is one of the Amazonian regions most threatened by forest loss and the formal description of new species adds impetus to support conservation strategies.

http://zoobank.org/urn:lsid:zoobank.org:act:8F14DC28-DD0C-498C-B27D-113264EBE7CE2F0A

Key words:

• advertisement call
• Amazonian biodiversity
• behaviour
• conservation
• integrative taxonomy
• morphology
• Rhinella margaritifera species group
• upper Madeira Basin

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgements

This study was supported by FAPEAM/CNPq (PRONEX proj. 003/2009, proc. 653/2009), the Harvard Museum of Comparative Zoology and the David Rockefeller Center for Latin American Studies of Harvard University. We are indebted to Miguel Vences and Natan Maciel for reviewing the first draft of this manuscript; David Gower, Antoine Fouquet and an anonymous referee for providing important suggestions that greatly improved this manuscript. We thank the Wildlife Conservation Program of Santo Antonio Energia for supporting fieldwork at Porto Velho; R. Ávila for sharing data on R. proboscidea and R. parecis; U. Suendel, J. Pereira, P. I. Simões, I. L. Kaefer, J. Dayrell, R. de Fraga, M. C. Araújo, M. Prestes, L. Vasconcelos and E. Vasconcelos for assistance with fieldwork; M. Franzen and K. Milto for photographs of the holotypes under their care at Zoologische Staatssammlung Museum (Germany) and Zoological Institute, Russian Academy of Sciences (Russia), respectively; and F. P. Werneck (INPA-H), A. Silva (INPA-H) and W. Vaz-Silva (CEPB) for access to herpetological collections. We thank BIOWEB Ecuador and Pontificia Universidad Católica del Ecuador (PUCE) for making public the data and photographs of specimens housed at QCAZ. Miquéias Ferrão received a fellowship from CNPq (PDJ process 154325/2018-0), an Edward O. Wilson Biodiversity Postdoctoral Fellowship from the Harvard Museum of Comparative Zoology and a fellowship from the David Rockefeller Center for Latin American Studies of Harvard University; Romildo A. Souza received a research fellowship of the FAPEAM and CNPq. Photographs of preserved specimens were taken with equipment acquired under the grant PRONEX/FAPEAM (ed. 016/2006, proc. 1437/2007).

Supplemental material

Supplemental material for this article can be accessed here: https://doi.org/10.1080/14772000.2022.2039317.

Associate Editor: Dr David Gower

Additional information

Funding

This work was supported by the Fundação de Amparo à Pesquisa do Estado do Amazonas – FAPEAM and National Council for Scientific and Technological Development – CNPq under grant PRONEX (proj. 003/2009, proc. 653/2009), the Harvard Museum of Comparative Zoology and the David Rockefeller Center for Latin American Studies of Harvard University.