The antbirds are a large passerine family found across subtropical and tropical Central and South America. Hybridization has been documented in several genera.
At Amazonian headwaters, hybrids between the following species pairs have been confirmed genetically (Weir et al., 2015):
- Rondonia Warbling Antbird (Hypocnemis ochrogyna) x Spix’ Warbling Antbird ( H. striata)
- White-breasted Antbird (Rhegmatorhina hoffmannsi) x Bare-eyed Antbird ( R. gymnops)
- Scale-backed Antbird (Willisornis poecilinotus) x Xingu Antbird (W. vidua)
Reproductive isolation between Scale-backed and Xingu Antbird and between Rondonia Warbling Antbird and Spix’ Warbling Antbird is mainly driven by postzygotic isolation (Pulido-Santacruz et al. 2018, Cronemberger et al., 2020).
A study on the Ash-breasted Antbird (Myrmoborus lugubris) uncovered a hybrid zone between the subspecies femininus and lugubris (Thom et al., 2018).
In 1951, American ornithologist Rodolphe Meyer de Schauensee described a new bird species: the Argus Bare-eyed (Phlegopsis barringeri). This new species of antbird was based on one specimen, collected on the Rio Rumiyaco in Colombia. Later, Willis (1979) suggested that the specimen might be a hybrid between Black-spotted Bare-eye (P. nigromaculata) and Red-winged Bare-eye (P. erythroptera). These two species overlap from eastern Colombia to northern Bolivia. This suggestion was tested by Graves (1992), who reexamined the original specimen and compared it to the two putative parental species. His conclusion: it’s a hybrid!
The white-shouldered fire-eye (Pyriglena leucoptera) and the fringe-backed fire-eye (P. atra) hybridize in the Atlantic Forest. In addition, several populations from the white-shouldered fire-eye interbreed at different contact zones (Sotelo-Muñoz et al., 2020).
Based on mitochondrial DNA, Brumfield (2005) described several hybrid zones between subspecies of the Variable Antshrike (Thamnophilus caerulescens). This result was confirmed with more extensive sampling and nuclear DNA (Bolívar-Leguizamón et al., 2020).
Bolívar-Leguizamón, S. D., Silveira, L. F., Derryberry, E. P., Brumfield, R. T., & Bravo, G. A. (2020). Phylogeography of the Variable Antshrike (Thamnophilus caerulescens), a South American passerine distributed along multiple environmental gradients. Molecular Phylogenetics and Evolution, 148, 106810.
Brumfield, R. T. (2005). Mitochondrial variation in Bolivian populations of the variable antshrike (Thamnophilus caerulescens). Auk 122, 414-432.
Cronemberger, Á. A., Aleixo, A., Mikkelsen, E. K., & Weir, J. T. (2020). Postzygotic isolation drives genomic speciation between highly cryptic Hypocnemis antbirds from Amazonia. Evolution, 74(11), 2512-2525.
Graves, G. (1992). Diagnosis of a hybrid antbird (Phlegopsis nigromaculata× Phlegopsis erythroptera) and the rarity of hybridization among suboscines. Proceedings of the Biological Society of Washington 105, 838-840.
Thom, G., Raposo do Amaral, F., Hickerson, M.J., Aleixo, A., Araujo-Silva, L.E., Ribas, C.C., Choueri, E. & Miyaki, C.Y. (2018) Phenotypic and Genetic Structure Support Gene Flow Generating Gene Tree Discordances in an Amazonian Floodplain Endemic Species. Systematic Biology.
Pulido-Santacruz, P., Aleixo, A. & Weir, J.T. (2018) Morphologically cryptic Amazonian bird species pairs exhibit strong postzygotic reproductive isolation. Proceedings of the Royal Society B, 285:20172081.
Sotelo-Muñoz, M., Maldonado-Coelho, M., Svensson-Coelho, M., dos Santos, S. S., & Miyaki, C. Y. (2020). Vicariance, dispersal, extinction and hybridization underlie the evolutionary history of Atlantic forest fire-eye antbirds (Aves: Thamnophilidae). Molecular Phylogenetics and Evolution, 106820.
Weir, J. T., Faccio, M. S., Pulido-Santacruz, P., Barrera-Guzman, A. O. & Aleixo, A. (2015). Hybridization in headwater regions, and the role of rivers as drivers of speciation in Amazonian birds. Evolution 69, 1823-1834.
Willis, E. O. (1979). Comportamento e ecologia da maede-taoca, Phlegopsis nigromaculata (d’Orbigny & Lafresnaye)(Aves, Formicariidae). Rev. Brasil Biol 39, 117-159.