Proposal (739) to South American Classification Committee
Elevate Paroaria baeri xinguensis to species rank
Background: From SACC notes: “Lopes & Gonzaga (2013) provided additional rationale for treating xinguensis as a separate species from P. baeri.” Previously, Proposal #469 to elevate xinguensis (and cervicalis) to species rank (following Dávalos and Porzecanski 2009) did not pass.
Paroaria baeri xinguensis was described from eight specimens collected on the Diauarúm, Rio Xingu, state of Mato Grosso (Sick 1950). Geographical coordinates of this site are: 1112S /5314W. At present, this taxon is known from only four localities (Lopes & Gonzaga 2013).
The main diagnostic character between Paroaria b. baeri and P. b. xinguensis is the extent of the dark crimson throat patch. The nominate subspecies has the entire upper throat dark crimson and P. b. xinguensis has a throat that is mostly black in color, only the malar streak being dark crimson (Ridgely and Tudor 1989).
The two subspecies of lowland and riparian P. baeri are allopatric, occurring in a transition zone between the savannas and the Amazon forest, and use a similar habitat. P. b. baeri is endemic to the Cerrado, being restricted to the Rio Araguaia and its tributaries. Paroaria b. xinguensis is endemic to the Upper Rio Xingu valley in the state of Mato Grosso. Drainages of the upper Rio Xingu and the Rio das Mortes (a western tributary of the Rio Araguaia) are separated by the Serra do Roncador. Riparian habitats are only found down the valleys.
Additional rationale provided by Lopes & Gonzaga (2013) for treating xinguensis as a separate species:
ü Taxa P. b. baeri and P. b. xinguensis are clearly diagnosable by plumage;
ü They are distinct in the absence (Paroaria baeri baeri) and presence (Paroaria baeri xinguensis) of sexual dichromatism;
ü They are separated by a sharp (about 100 km) geographic barrier
These observations are consistent with the lack of gene Ŗow between both taxa. Under the Phylogenetic Species Concept or the General Lineage Concept of Species lineages these two lineages will consider them as distinct species.
It seems to me that under the BSC the treatment must remain unchanged.
Dávalos L. M. and A.L. Porzecanski. 2009. Accounting for molecular stochasticity in systematic revisions: species limits and phylogeny of Paroaria. Molecular Phylogenetics and Evolution 53:234–248.
Ridgely R. S. and G. Tudor. 1989. The birds of South America, vol. 1, the oscine passerines. Austin: University of Texas Press.
Sick H. 1950. Uma nova raća de cardeal procedente do Brasil central Paroaria baeri xinguensis n. ssp. (Fringillidae, Aves). Revista Brasileira de Biologia 10:465–468.
Fernando Pacheco, January 2017
Comments from Remsen: “NO. Diagnosability in plumage validates its current status as a valid subspecies under BSC framework (see my 2010 paper on subspecies in Ornithological Monographs). Elevation to species rank would require evidence that these two taxa have diverged to the level associated with species rank in Paroaria and relatives. If a comparative analysis of phenotypic characters indicates that xinguensis is as divergent as other taxa treated in the baeri-gularis-nigrogenis-capitata group, I would change my vote. Anything known about voice in these birds?” On the other hand, species limits in this complex are poorly supported (as indicated in our SACC footnotes), and someone should undertake a re-evaluation of current classification.
Comments from Stiles: “NO. Again, data presented could justify recognizing it as a distinct phylogenetic species, but more detailed analysis including more taxa in this genus, including vocalizations and hopefully, playback experiments, that would clinch things regarding the BSC, are currently lacking. I agree with Fernando that for SACC, no change in its status as a subspecies is currently justified.
“It seems as though we are presently witnessing a tendency (or an epidemic, if one prefers – which might be termed the “species-itch” in Couesian terminology) of finding allopatric but evidently related subspecies and splitting them off as species, based principally if not exclusively on diagnosability using museum specimens. The advocates of such splitting usually do not present pertinent field data on features that could justify splitting under the BSC, especially vocalizations, which in many groups (like the oscines in particular), should be backed up by playback experiments, perhaps accompanied by presentation of models/mounts to compare reactions of taxa in question to vocal vs. visual stimuli. Genetic data are often suggestive but not always decisive. A spot of field work would be necessary and sufficient in many such cases, and knowing their subjects in the field would do many of the proponents no harm either!”
Comments from Areta: “NO, for two main reasons. First, the differences between males and females of xinguensis have been overstated in the literature. I examined photographs of all known specimens of xinguensis and sexual dimorphism appears to be more subtle than reported by Lopes and Gonzaga (2013): some males approach the condition of females, reducing the taxonomic value of such a purported dimorphism, which is in need of more thorough documentation. Second, in a forthcoming paper (Areta et al. in press) we show that P. b. baeri hybridizes with the very distinct and non-sister P. gularis. This suggests that no strong interbreeding barriers would probably exist between the likely sisters P. b. baeri and P. b. xinguensis. Until compelling biological evidence is presented, I support treatment of xinguensis as a subspecies of P. baeri.
“Answering Van's question on the vocalizations, there are few recordings of P. b. baeri (and none of xinguensis) available for analysis in sound archives [http://macaulaylibrary.org/audio/220188, http://www.xeno-canto.org/species/Paroaria-baeri]. The taxonomy of Paroaria is in need of some serious study, especially near the geographic boundaries of some taxa that have been proposed to be good species (e.g., nigrogenis-gularis, cervicalis-capitata).
Areta, J.I., Kirwan, G., Dornas, T., Araujo-Silva, L.E. & A. Aleixo. in press. Mixing the waters: a linear hybrid zone between two riverine Neotropical cardinals (Paroaria baeri and P. gularis). Emu http://dx.doi.org/10.1080/01584197.2016.1266447”
Comments from Stotz: “NO, with the lack of vocal evidence I cannot see any way to consider these as distinct species. The reported differences in sexual dimorphism is interesting and suggests it is worth looking at this pair in more detail, but by itself is not sufficient to lead to treatment as distinct species.”
Comments from Cadena: “NO, for reasons noted in the proposal and in comments by other committee members.”
Comments from Robbins: "NO for now, until more data become available."
Comments from Jaramillo: “NO. I still consider my suggestion to retain xinguensis as a subspecies in the previous Paroaria proposal to be valid.”