https://orcid.org/0000-0003-4060-0281
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Abstract
The accumulation of studies delimiting species in Amazonia has not only shed light on the patterns of its outstanding species richness but also allowed a better understanding of the processes of diversification within this immense region. Nevertheless, vast knowledge gaps remain even for prominent anuran species complexes, such as the Rhinella margaritifera species group. This clade of toads comprises 23 valid species-level taxa, mainly distributed in Amazonia but also in South America’s Dry Diagonal and Atlantic and trans-Andean rainforests. Species boundaries and taxonomy in this group are notoriously complex, with studies suggesting the existence of several unnamed species. Available phylogenetic information suggests an Andean-western Amazonian origin of the group with subsequent diversification within Amazonian lowlands during the last 10 Myr and secondary dispersals into other Neotropical regions. To further test this biogeographic scenario and improve knowledge on species diversity, we used an unprecedentedly large mtDNA sampling (>800 16S sequences) across the clade’s distribution and comprising all but one described species. We delimited 54 Molecular Operational Taxonomic Units, which we tested further based on patterns of variation of a nuclear locus and acoustic and morphological data. This approach confirmed the existence of at least 25 candidate species, 19 of which correspond to currently recognized taxa whereas 30 remained ‘unconfirmed’. Our results clarify the taxonomic status of some species but also suggest multiple introgression events that blur some mtDNA-based species boundaries. Lastly, to provide a temporal framework for the clade’s diversification, we generated a time-calibrated phylogenetic tree based on a mitogenomic matrix, which confirmed a Miocene (∼9 Ma) western Amazonian origin and six major clades in the group, each having initially diversified in different regions within Amazonia. Most of these clades have later dispersed throughout Amazonia during the establishment of the modern Amazonian hydrographic system, i.e., in the last 6 Myr.
Acknowledgements
We warmly thank the following colleagues for having contributed in collecting material in the field: J. Rengifo, J. Padial, M. Medina, S. Logan, J. Allen, A. Rejaud, J. Chretien, V. Premel, M. Chouteau, F. Dal Vechio, P. Peloso, S.R. Malqui, A.F. Souza-Oliveira, L.F. Martins, R. de Fraga, M. Teixeira Jr., S.M. de Souza, M.A. Sena, F.A.D. Esteves; V.C.D. Bernardes, J.A. Ochoa, J.P. Vacher, S. Cally, R. Gallais, F. Catzeflis, J. Cuisin, O. Chaline, M. Dewynter, C. Marty, V. Rufray, E. Courtois, Q. Martinez, B. Villette, H. Foxonet, T. Le pape, E. Campos, A.F. Souza-Oliveira, D. Oliveira, J. Vieira, L. Frazão, L. Bonora, O. Pereira, A. Picelli, W. Spindola, A.A.A. Silva, I. Junqueira, A.F. Palmerim, D. Oliveira, E. Ribeiro, G. Dias, M. Nunes, O. Colatrelli, R. Kautmaz, E. Pontes, L. Viegas, L. Crisley, R.M. Pirani, J. César, P. Dias, J.M. Guellere, R. Quispe, P.F. Condori, J.G. Estrada, E.A. Aguilar M., J. Devillechabrolle, A. Baglan, K. Pineau, P. Gaucher, C. Bedeau, M. Blanc, D. Moraes, B. Rojas, A. Jaramillo, I. Rey, J. Delgado, D. Baeta, R. Jairam, J. Cassimiro, A. Snyder, S. Neilsen, B.P. Noonan, A. Picelli, W. Spindola, S. Neckel, P. Pérez, G. Estrada, S. Anjos, R. A. Kawashita-Ribeiro, D.H. Morais, A.R.L. Ramos. We are also indebted to S. Manzi, Y. Cuenot, U. Suescun, and L. Moreau for their help in the lab, to J. Chretien for preliminary analyses, and to Olivier Jansen for insights on the fossils of bufonids. We thank curatorial staff for processing biological samples at: the Amphibians and Reptiles Collection at INPA (INPA-H: F.P. Werneck; A.A. Silva) and Genetic Resources Collection-Herpetofauna (CRG/INPA-HT: C. Ribas; M. Freitas); at USP (J.N. Tanaka). The Fonoteca Neotropical Jacques Vielliard (FNJV) enabled access to sound files. We wish to thank two anonymous reviewers for their engagement with this work.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Supplemental material
Supplemental material for this article can be accessed here: https://doi.org/10.1080/14772000.2023.2291086.
Associate Editor: Dr David Gower