Proposal (867) to South American Classification Committee
Transfer “Thraupis/Pipraeidea” bonariensis to its own genus (Rauenia)
The Blue-and-yellow Tanager (historically treated as Thraupis bonariensis) has been recently found as sister to the Fawn-breasted Tanager (Pipraeidea melanonota) based on molecular data. As a result, most subsequent classifications lumped both species under a single genus, Pipraeidea.
In Piacentini (2017), I showed that both species differ markedly in plumage (color, pattern, and degree of sexual dichromatism), morphology, voice, and behavior (diet, foraging, and nesting), and that the treatment of the Blue-and-yellow Tanager in Pipraeidea creates an undiagnosable genus contrasting greatly with the generic limits commonly applied to the tanagers.
Remarkably, each species looks more similar to a more distantly related tanager than to each other. In plumage, Pipraeidea is much closer to Dubusia castaneoventris than it is to T. bonariensis. In morphology, T. bonariensis resembles some Thraupis, which explains its historical treatment in that genus. In its diet and behavior, Pipraeidea is quite similar to Nemosia, whereas T. bonariensis is again more similar to Thraupis sayaca and other congeners.
These species are much more divergent from each other, both phenotypically and genetically, than many other pairs of sister or closely related genera in the family (e.g. Ramphocelus vs. Tachyphonus; Idiopsar vs. Chionodacryon; Spodiornis vs. Acanthidops; Wetmorethraupis vs. Bangsia; Neothraupis vs. Diuca; or even the five genera formerly treated collectively under Tangara among themselves; see Burns et al. 2016). Thus, I suggest Pipraeidea melanonota and the Blue-and-yellow Tanager be treated in distinct genera.
Based on all the above, I had proposed a new genus for bonariensis (Piacentini 2017), which unfortunately proved to be a junior objective synonym of Rauenia Wolters, 1981 (Piacentini et al. 2019). Therefore, following the ICZN, I here propose to SACC to treat the Blue-and-yellow Tanager as Rauenia bonariensis.
Burns, K.J., Unitt, P. & Mason, N.A. (2016) A genus-level classification of the family Thraupidae (Class Aves: Order Passeriformes). Zootaxa, 4088 (3), 329–354.
Piacentini, V.Q. (2017) A new genus for the Blue-and-yellow Tanager (Aves: Passeriformes): a suggested adjustment to the classification of the Thraupidae. Zootaxa, 4276 (2), 293–300.
Piacentini, V.Q., Unitt, P. & Burns, K.J. (2019) Two overlooked generic synonyms in the Thraupidae (Aves: Passeriformes). Zootaxa, 4608 (3), 593–594.
Vítor Q. Piacentini, July 2020
Comments from Remsen: “YES. I think recognizing two genera makes the most sense. As Vitor outlines, these two differ strongly in phenotype, and the sister relationship was thus completely unanticipated. More importantly to me, the comparative node depth and genetic divergence in the Thraupidae is closer in this pair to that between genera rather than between congeners, thus facilitating comparisons among taxa.”
Comments from Stiles: “YES. As in 866, required by the genetic data, and in agreement with considerable data on morphology and natural history.”
Comments from Areta: “YES. It never made sense to have both species in the same genus, given the deep branch length and the multiple differences in natural history and vocalizations (Rauenia apparently completely lacks the long, complex song that is given, sometimes, by Pipraeidea). I have been using Rauenia for some time in my notes and recordings, so it is relieving to see Rauenia bonariensis being used, and a pity to have Remsenornis as a junior synonym.”
Comments from Claramunt: “YES. I think that proposing a classification with sister monotypic genera requires some further quantitative analysis (of diagnosability, heterogeneity, etc) but in the end, I agree that in this case lumping these two species under the same genus is unsatisfactory.”
Comments from Robbins: “YES, for reasons outlined by Vitor, for transferring bonariensis to Rauenia.”
Comments from Stiles: “YES to placing bonariensis in a monotypic Rauenia: it clearly is not a Thraupis, its sister relationship to Pipraeidea is not all that close, and it does differ considerably from the latter in plumage.”
Comments from Zimmer: “YES for all of the reasons already stated by Vitor in the Proposal, and by others who have commented so far. Looking back at Proposal #437, I voted against moving bonariensis into Pipraeidea at that time, because, aside for some gross similarities in coloration, they have always struck me as vocally, morphologically and ecologically very different creatures, all recent genetic revelations aside.”
Comments from Jaramillo: “YES - These two tanagers are not all that closely related and are not at all similar. As such, recognizing Rauenia seems like a good option.”
Comments from Bonaccorso: “YES. Very deep genetic divergence and plumage incoherency of a broad Pipraeidea justify the change.”
Comments from Pacheco: “YES, fully agreeing with treatment in a genus apart.”