Proposal (286) to South American Classification Committee
Revive the genus Dichropogon
Effect on SACC: Hylophylax poecilinotus would change to Dichropogon poecilinotus.
Background & New information: Zimmer and Isler (2003) noted that Hylophylax poecilinotus may not be closely related to other members of the genus, and that it may prove to be part of an obligate ant-following clade.
A new molecular phylogeny of the family Thamnophilidae (Brumfield et al. in press) included individual samples of Hylophylax poecilinotus, H. naevioides, and H. punctulatus as well as 67 other thamnophilid taxa. With strong bootstrap and Bayesian support in a phylogenetic analysis of mitochondrial and nuclear genes, H. poecilinotus occurred in a clade of obligate army-ant following birds that included Phlegopsis, Rhegmatorhina, Pithys, Gymnopithys, Phaenostictus (Skutchia was not sampled).
Elsewhere in the phylogeny H. naevioides and H. punctulatus occurred as a clade sister to Hypocnemoides maculicauda. Although an individual of H. naevia was not included in the study, Brumfield downloaded a cytochrome b sequence of that taxon (GenBank accession number AY676963) from the Irestedt et al. (2004) study, and, based on a parsimony analysis of that gene, H. naevia is sister to H. naevioides.
The ant-following clade that includes H. poecilinotus is not sister to the clade with the other three Hylophylax species, and is in fact relatively distant in the phylogenetic tree. Thus, a distinct genus name for one of the two is warranted. The type taxon of Hylophylax is H. naevioides (Ridgway 1909), thus H. naevia, H. naevioides, and H. punctulatus would retain that genus.
For H. poecilinotus, Chubb's (1918) description of Dichropogon seems to meet the requirements for the description of a new genus (even though it is minimal). Dichropogon is masculine so Chubb erred in naming the type species D. poecilinota. It should be Dichropogon poecilinotus, which is consistent with the currently accepted masculine gender for the species name.
The proposal here is to change the name of Hylophylax poecilinotus to Dichropogon poecilinotus.
Brumfield, R. T., J. G. Tello, Z. A. Cheviron, M. D. Carling, and N. Crochet. in press. Phylogenetic conservatism and antiquity of a tropical specialization: army-ant-following in the typical antbirds (Thamnophilidae). Molecular Phylogenetics and Evolution.
Chubb, C. 1918. Descriptions of new genera and a new subspecies of South American birds. Annals and Magazine of Natural History (Ser. 9) 2:122-124.
Irestedt, M., Fjeldså, J., Nylander, J.A.A., Ericson, P.G.P., 2004. Phylogenetic relationships of typical antbirds (Thamnophilidae) and test of incongruence based on Bayes factors. BMC Evol. Biol. 4.
Ridgway, R. 1909. New genera, species and subspecies of Formicariidae, Furnariidae, and Dendrocolaptidae. Proceedings of the Biological Society of Washington 22:69-74.
ZIMMER-ISLER. HBW chapter on Thamnophilidae.
Robb Brumfield (in consultation with Mort Isler, Storrs Olson, and Richard Banks), June 2007
Comments from Stiles: "YES. I have never felt comfortable with poecilinotus in Hylophylax in any case: it looks, acts and sounds quite different and its plumage bears a considerable resemblance to some of the Rhegmatorhina-Phlegopsis-Phaenostictus group, from which the lack of a bare eyering is the most striking difference and could well merit its separate generic status in this group."
Comments from Cadena: "YES. The data are solid, and because this taxon appears to be sister to a clade that includes all the professional ant-followers, a monotypic genus is the best possible alternative. The only other possibility would be to merge all members of that clade in a single genus, which does not seem to be a sensible option."
Comments from Remsen: "YES. Solid genetic data refute monophyly of Hylophylax as currently defined, and an expanded Hylophylax would make that genus too heterogeneous to be consistent with generic limits in Thamnophilidae."
Comments from Zimmer: "YES. Molecular data supporting the sister status of poecilinotus to all sampled obligate army-ant followers appear strong, and this squares well with ecological considerations as well as some plumage and vocal characters. Minus poecilinotus, Hylophylax as a cohesive, monophyletic group makes a lot more sense. The obligate army-ant followers are too heterogeneous as a whole to lump into a single genus, with several well defined groups (Rhegmatorhina, Phlegopsis, Gymnopithys, Pithys) and a few oddballs (Skutchia, Phaenostictus) that are not clearly aligned with anything else. The latter have traditionally been treated in their own genera, and I think that is the way to go with poecilinotus as well."
Comments from Nores: "NO. Aunque no pongo en dudas lo que dice Brumfield, no me parece lógico aceptar una propuesta en base a comentarios de un trabajo propio que todavía no está publicado, ni figura en la lista "online" de trabajos en prensa de Molecular Phylogenetics and Evolution. Cuando salga el paper, se verá si la propuesta es convincente."
Comments from Jaramillo: "YES- Data solid, creates a more intuitively cohesive Hylophylax as well."