Proposal (151) to South American Classification Committee
Merge Baillonius into Pteroglossus
Effect on South American CL: This would merge a monotypic genus (Baillonius) that we recognize into a polytypic genus (Pteroglossus).
Background: The monotypic genus Baillonius has been recognized for Baillonius for most of ornithological history. Baillonius has some unique plumage features in the family (yellowish green back and head), and it also differs from Pteroglossus in bare part coloration (bill and eyering) and relative tail length (longer). However, its close relationship to Pteroglossus has also been long recognized, based on their sharing of certain phenotypic characters, i.e., vocalizations (Short & Horne 2001; but cf. Haffer 1974, Sick 1993) and general behavior and morphology (Haffer 1974, Sick 1993). Overall, its bill and facial pattern is more similar in some respects to that of P. viridis or P. azara than those of many Pteroglossus are to each other (see illustrations in HBW). Pteroglossus and Baillonius share red uppertail coverts, unique in Ramphastidae. Kimura et al. (2004) also cited Höfling's thesis on cranial similarities, including two synapomorphic characters.
Genetic data has been accumulating for a close relationship between the two genera. Hackett & Lehn's (1997) allozyme data indicated that Baillonius was the sister to Pteroglossus (11 taxa) compared to Selenidera and Ramphastos. DNA sequence data (Barker & Lanyon 2000, Nahum et al. 2003, Moyle 2004, Weckstein 2004) provided further genetic evidence for the close relationship of the genera, but insufficient taxon-sampling of Pteroglossus species precluded determination of whether Baillonius was embedded within Pteroglossus.
New information: Kimura et al. (2004) collected sequence data from GenBank and sequenced cytochrome b from blood samples of Baillonius and 3 Pteroglossus to produce a phylogenetic hypothesis for the group, with 2 Aulacorhynchus, 4 Selenidera, two Andigena, and two Ramphastos included. Their data, whether analyzed by parsimony, likelihood, or Bayesian methods, produced similar topologies, with Baillonius falling within Pteroglossus, with strong bootstrap or posterior probability support for Pteroglossus + Baillonius as a monophyletic group, and reasonably good support (88% bootstrap ML, 67% bootstrap MP, 98% pp Bayesian) for a sister relationship between P. inscriptus and Baillonius. (Unfortunately, P. viridis sequence was not available; by conventional standards, P. viridis and P. inscriptus are allospecies). Not mentioned by Kimura et al. is that P. viridis-P. inscriptus and Baillonius are the only members of this group with unbanded yellow underparts.
Analysis: Although Kimura et al. are missing some Pteroglossus (viridis, azara, pluricinctus) and had only 1045 bp of cytochrome b, it seems unlikely that more sequence and taxa would affect the overall outcome of the analysis, namely Baillonius is embedded in Pteroglossus. I think the burden of proof at this point would be to provide rationale for maintaining the monotypic Baillonius based mainly on unique back and head coloration (that might only be a consequence of degree of pigment saturation).
Recommendation: I see no reason not to follow the recommendation of Kimura et al. (2004) for merging Baillonius into Pteroglossus.
BARKER, F. K., AND S. M. LANYON. 2000. The impact of parsimony weighting schemes on inferred relationships among toucans and Neotropical barbets (Aves: Piciformes). Molecular Phylogenetics and Evolution 15: 215-234.
HACKETT, S. J., AND C. A. LEHN. 1997. Lack of divergence in a genus (Pteroglossus) of Neotropical birds: the connection between life-history characteristics and levels of genetic divergence. Pp. 267-279 in "Studies in Neotropical ornithology honoring Ted Parker." Ornith. Monogr. 48.
HAFFER, J. 1974. Avian speciation in tropical South America. Publications of the Nuttall Ornithological Club, No. 14.
KIMURA, R. K., S. L. PEREIRA, E. T. GRAU, E. HÖFLING, AND A. WAJNTAL. 2004. Genetic distances and phylogenetic analyses suggest that Baillonius Cassin, 1867 is a Pteroglossus Illiger, 1811 (Piciformes, Ramphastidae). Ornitologia Neotropical 15: 527-537.
NAHUM, L. A., S. L. PEREIRA, F. M. C. FERNANDES, S. R. MATIOLI, AND A. WAJNTAL. 2003. Diversification of Ramphastinae (Aves, Ramphastidae) prior to the Cretaceous/Tertiary boundary as shown by molecular clock of mt DNA sequences. Genetics Molecular Biology 26: 411-418.
SHORT, L. L., AND J. F. M. HORNE. 2001. Toucans, barbets and honeyguides. Oxford University Press, Oxford.
SICK, H. 1993. Birds in Brazil. Princeton Univ. Press, Princeton, New Jersey.
WECKSTEIN, J. D. 2004. Biogeography explains cophylogenetic patterns in toucan chewing lice. Systematic Biology 53: 154-164.
Van Remsen, December 2004
Comments from Robbins: "YES. This is a straightforward decision as Kimura et al. (2004) provided unequivocal genetic data demonstrating Baillonius is imbedded within Pteroglossus."
Comments from Pacheco: "YES. O trabalho de Kimura e colegas oferece o suporte necessário (confirmando sugestões prévias) para o acatamento de tal proposta."
Comments from Jaramillo: "YES -- I am in agreement, this is a straight forward decision. There is nothing that points to it being otherwise, it is a species with a divergent upperpart colouration but given the extreme diversity in colouration in this group, that does not bother me. Vocal and structural differences appear to be more important in this group than plumage colour, from these perspectives Baillonius also is fine for inclusion in Pteroglossus."
Comments from Stiles: "YES. The position of Baillonius within Pteroglossus leaves only one alternative if one wishes to maintain Baillonius as a genus, which would be to split Pteroglossus into several little genera which would only obscure, rather than highlight, relationships in this group."
Comments from Nores: "YES; estoy de acuerdo. A pesar de que desde un punto de vista ornitológico ambos géneros aparecen como bastante distintos (especialmente cuando se comparan las dos especies que coexisten: Baillonius y Pteroglossus castanotis) los estudios genéticos aparecen como mucho más concluyentes. Además, es notable que ambos géneros sean los únicos tucanes con rabadilla roja."
Comments from Silva: "YES. I think that the evidence presented is strong enough."
Comments from Zimmer: "YES. The molecular data seem convincing, and both vocal characters and behavioral/ecological characters support it as well."