Proposal (740) to South American Classification Committee
Recognize the genus Oneillornis (Thamnophilidae)
Effect on SACC: This proposal would move two species, currently Gymnopithys salvini and G. lunulatus, into a newly described genus Oneillornis.
Background and analysis: Building on molecular data presented by Brumfield et al. (2007) and adding newly obtained sequences, a molecular phylogeny was constructed of the core complex of army-ant-following genera of the Thamnophilidae (Isler et al. 2014). Maximum-likelihood and Bayesian analysis produced similar typologies indicating with high support that the complex contained five well-supported principal clades. Among currently recognized genera, only Gymnopithys was recovered as non-monophyletic. The Gymnopithys/Rhegmatorhina principal clade included three subclades: (a) the rufigula clade containing G. leucaspis and G. rufigula; (b) the lunulatus clade containing G. lunulatus and G. salvini; and (c) the gymnops clade containing the five Rhegmatorhina species. Although the basal node of this principal clade was unresolved, the results as well as those of Brumfield et al. (2007) indicated with high support that the rufigula, lunulatus, and gymnops subclades represent distinct lineages. Also, we should mention that, although not published yet, genomic data (~2300 UCE loci + 100 exons) are strongly supporting Oneillornis (Bravo et al. unpublished data).
The phylogeny was then overlaid with a variety of morphological and behavioral characters. The major differences among the three subclades of the Gymnopithys/Rhegmatorhina principal clade were in their plumages (illustrated in Zimmer and Isler 2003). Species in the rufigula subclade are monomorphic (except for interscapular patches in one species); blue periorbital patch; upperparts predominantly brown; center of underparts white or cinnamon; no scaling or barring. Species in the lunulatus subclade are dimorphic: males predominantly gray with supercilium, chin, and throat white, and females predominantly brown with back barred and tail barred or spotted. Species in the gymnops subclade are dimorphic; both sexes share a short crest, light periorbital patches surrounded by a blackish mask in most species, and plain brownish tail; males with upper parts predominantly brown; females predominantly brown with blackish spots on back (most species).
Recommendation: Given the substantial distinctions between them in plumage, consolidating Gymnopithys and Rhegmatorhina into a single genus (Gymnopithys has priority) is inconsistent with the ‘‘focused monophyly’’ approach to generic definition which maintains that recognizing phylogenetic relationships, genetic divergence and phenotypic distinctiveness best facilitates understanding of relatedness of taxa (Isler et al 2013). Merging Rhegmatorhina into Gymnopithys was rejected by SACC earlier (Proposal 445). However, if the genus Rhegmatorhina is recognized, plumages of the rufigula and lunulatus subclades are also distinct, and the genetic analysis indicates that they cannot be maintained in the same genus under the principle of monophyly. We recommend therefore that Rhegmatorhina be maintained, that Gymnopithys be restricted to the rufigula subclade, and that species in the lunulatus subclade be placed in the genus Oneillornis Isler, Bravo, and Brumfield, 2014.
Brumfield, R. T., J. G. Tello, Z. A. Cheviron, M. D. Carling, N. Crochet, and K. V. Rosenberg. 2007. Phylogenetic conservatism and antiquity of a tropical specialization: Army-ant-following in the typical antbirds (Thamnophilidae). Molecular Phylogenetics and Evolution 45:1–13.
Isler, M. L., G. A. Bravo, and R. T. Brumfield. 2013. Taxonomic revision of Myrmeciza (Aves: Passeriformes: Thamnophilidae) into 12 genera based on phylogenetic, morphological, behavioral, and ecological data. Zootaxa 3717 (4): 469–497.
Isler, M. L., G. A. Bravo, and R. T. Brumfield. 2014b. Systematics of the obligate ant-following clade of antbirds (Aves: Passeriformes: Thamnophilidae). Wilson Journal of Ornithology 126:635–648.
Zimmer, K. J., and M. L. Isler. 2003. Family Thamnophilidae (typical antbirds). Pages 448–681 in Handbook of the Birds of the World. Volume 8: Broadbills to Tapaculos (J. del Hoyo, A. Elliot, and D. A. Christie, Editors). Lynx Edicions, Barcelona, Spain.
Morton L. Isler, Gustavo A. Bravo, & Robb T. Brumfield
Comments from Stotz: “YES. Lunulata and salvini have never seemed much like the other Gymnopithys to me. So it does not surprise me too much that Gymnopithys as currently defined is not monophyletic. I would agree that lumping Rhegmatorhina into Gymnopithys creates a too variable genus, so I favor this split.”
Comments from Stiles: “YES. These two are so different in plumage from Gymnopithys that one wonders why they were ever consider congeneric in the first place, and with solid genetic support, I see no problem with this split.”
Comments from Cadena: “NO. I do not dispute the fact that the tree clades are well-supported groups not only in terms of DNA sequences but also in terms of morphology and behavior. However, unless I am not interpreting the published trees correctly, the node linking the salvini-lunulatus clade with Rhegmatorhina lacks strong support in phylogenetic analyses. I thus interpret the relationships among the three clades to be unresolved, implying no taxonomic changes are necessary for now. If the paraphyly of Gymnopithys is confirmed with additional data, I would be happy to reconsider.”
Comments from Jaramillo: “YES. I don’t find this one controversial, and lumping all into Gymnopithys is a less informative outcome.”
Comments from Zimmer: “YES, for all of the reasons spelled out in the Proposal. And NO to lumping Rhegmatorhina into Gymnopithys! Each of these three subclades is distinctive and internally consistent with respect to the other subclades, both in morphology, voice and behavior, and each should be recognized as a separate genus in my opinion.”
Comments from Areta: "YES. I understand Daniel's concern on the lack of support for paraphyly in Gymnopithys. However, even without a clear understanding of how these clades are related to each other, support for each clade is consistently good. Also, the plumage distinctions, especially the lack of bare periorbital skin in Oneillornis and the highly-reduced dimorphism in Gymnopithys sensu stricto, provide further support for a two-genera treatment. Keeping Gymnopithys as currently delineated is considerably worst at parsing out morphological, genetic and vocal variation than splitting it in Oneillornis and a restricted Gymnopithys."
Comments from Claramunt: "YES. Although the trees show a non-monophyletic Gymnopithys, the relevant nodes are not resolved with certainty. However, what the trees do show is that the Gymnopithys/Rhegmatorhina clade is composed of three clearly defined subclades which are also phenotypically coherent. For that reason, I think that a three-genera solution is convenient here (also serving to celebrate a great ornithologist!)."
Comments from Robbins: "YES, given that we are recognizing Rhegmatorhina, then we should treat the subclade composed of salvini and lunulatus at the generic level."
Comments from Pacheco: "YES. This treatment at the generic level for each clade seems to me to be more appropriate and informative. I like to know that genomic data (Bravo, unpublished yet) are strongly supporting Oneillornis."