Proposal (445) to South American Classification Committee

Merge Rhegmatorhina into Gymnopithys

Effect on SACC: This would move the thamnophilid genus Rhegmatorhina into Gymnopithys in a similar way to that of Skutchia borbae being moved into Phlegopsis (Proposal 432 of Robb Brumfield).

Background:  Ridgway (1888) erected the genus Rhegmatorhina for Rhegmatorhina gymnops, and later other authors included four species of antbirds were in this genus: R. berlepschi, R. cristata, R. hoffmannsi, and R. melanosticta.

New information: Recently, Aleixo et al. (2009) presented molecular evidence for the phylogenetic position of Rhegmatorhina. In their phylogeny, Rhegmatorhina melanosticta/gymnops/hoffmannsi occurred as the sister species of Gymnopithys leucaspis/rufigula. This sister relationship had very strong support: maximum-likelihood and parsimony bootstrap support were both 100 and Bayesian posterior probability was 1.0.

The Gymnopithys lunulatus/salvini clade was sister to Gymnopithys leucaspis/rufigula, also with high support.

Because Gymnopithys has priority over Rhegmatorhina and Gymnopithys rufigula over G. lunulatus/salvini, there are two taxonomic options for addressing this situation: (a) merging Rhegmatorhina and Gymnopithys into a single expanded genus Gymnopithys, or (B) erecting a new genus for the gray males with white throat antbirds: G. lunulatus/salvini.

However, after preparing this proposal, I saw the phylogenetic tree of Brumfield et al. (2007) in which Rhegmatorhina and Gymnopithys are well separated, also with high support, which again produces confusion within the molecular analyses.

I vote NO to this proposal mainly for subjective reasons: the genus Rhegmatorhina consists a morphologically similar group of parapatric taxa, with no clearly shared morphological similarities to Gymnopithys.

References:

ALEIXO, A., T. C. T. BURLAMAQUI, M. P. C. SCHNEIDER, AND E. C. GONÇALVES. 2009. Molecular systematics and plumage evolution in the monotypic obligate army-ant-following genus Skutchia (Thamnophilidae). Condor 111: 382-387.

BRUMFIELD, R. T., J. G. TELLO, Z. A. CHEVIRON, M. D. CARLING, AND N. CROCHET. 2007. Phylogenetic conservatism and antiquity of a tropical specialization: army-ant-following in the typical antbirds (Thamnophilidae). Molecular Phylogenetics and Evolution 45: 1-13.

Manuel Nores, July 2010

Comments from Remsen: “NO. If we were to merge sister genera just because that relationship was well established, then we’d eventually end up with just one genus. Using current subjective standards of delimiting generic boundaries, the two current genera are morphologically and ecologically coherent units.”

Comments from Cadena: “NO. I do not understand the rationale for this proposal because in the Aleixo et al. tree, the sister relationship between Rhegmatorhina and the clade formed by Gymnopithys leucaspis and G. rufigula, in contrast to what the proposal says, is *not* strongly supported. The G. rufigula-G. leucaspis clade, the Rhegmatorhina clade, and the G. lunulatus-G. salvini clade are each all well-supported, but support for the relationships among these three clades is nonexistent. The relevant node in the Brumfield et al. tree is not well-supported either. True, Rhegmatorhina and Gymnopithys are closely related genera, but there is no hard data to support lumping them, at least for now.”

Comments from Stotz: “NO. The molecular data does not currently require an adjustment of the taxonomy in this portion of the tree in my view. If the Aleixo et al topology eventually is confirmed, I would probably favor separating out lunulatus/salvini as a separate genus rather than creating a larger Gymnopithys.”