Proposal (150) to South American Classification Committee

Recognize Thamnophilus divisorius as a valid species

Effect on South American Check-List: This proposal would add a newly described species to our official list.

Background: Whitney, Oren, and Brumfield (2004) described a new species of antshrike, Thamnophilus divisorius, from Acre, Brazil. Their assignment of the species to Thamnophilus was based largely on vocal characters. Although morphological characters of the new species are not inconsistent with the generic allocation, justification based on morphology is difficult because no suite of diagnostic morphological characters has ever been elaborated for the genus, and, because the genus as currently constituted may not be monophyletic. Diagnosis of this taxon was supported by 8 specimens (4 males, 3 females, 1 sex undetermined) and tape recordings of at least 13 individuals. Molecular analysis resulted in 100% support for a sister relationship between the new species and T. insignis, a geographically remote species found in the Tepui region of southern Venezuela, Guyana, and adjacent northern Brazil.

Analysis:  T. divisorius is morphologically and vocally distinct from all other known antshrikes. Molecular analysis supports its recognition as a distinct species and its placement in Thamnophilus.

Recommendation: I recommend a "YES" vote on accepting this distinctive antshrike as a new species to our list. The English name of "Acre Antshrike," as suggested by the authors, seems well chosen.

Literature Cited:

WHITNEY, B. M., D. C. OREN, AND R. T. BRUMFIELD. 2004. A new species of Thamnophilus antshrike (Aves: Thamnophilidae) from the Serra do Divisor, Acre, Brazil. Auk 121: 1031-1039.

Kevin J. Zimmer, December 2004

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Comments from Remsen: YES. Solid evidence for treating divisorius as a valid, new species-level taxon."

Comments solicited from Mort Isler: "Our ongoing work supports consideration of Thamnophilus divisorius as a species. We have made a large number of measurements of vocal characters of Thamnophilus species in an ongoing phylogenetic study. Although the study is not designed to test species limits, it is obvious from the data that T. divisorius differs from all other Thamnophilus species in more than three vocal characters (defined at the level of Isler et al. 1998), our reference for species level distinctions in the Thamnophilidae. For example, loudsongs of T. divisorius appear to be diagnosable from those of T. insignis, its sister species as determined by genetic analysis, by pace, change of pace, predominant note shape, and structure of terminal notes."

Comments from Robbins: "YES. No question in recognizing Thamnophilus divisorius as a species as Whitney et al. provided solid justification."

Comments from Pacheco: "YES. Um veemente sim. O trabalho de Whitney, Oren e Brumfield ofereceu suficientes razões para considerar divisorius em nível de espécie."

Comments from Jaramillo: "YES -- This is a clearly good new species, supported by several different sets of data. I will also mention that Acre Antshrike is what I would go with for an English name."

Comments from Stiles: "YES. Again, clearly a distinct new species, and placement in Thamnophilus seems appropriate until further notice; Acre Antshrike an appropriate English name."

Comments from Nores: "YES. Estoy de acuerdo en considerar a Thamnophilus divisorius como una especie válida y "Acre Antshrike" como su nombre en inglés. Los fundamentos aportados por los autores son aparentemente lo suficientemente documentados como para justificar de que se trata de una nueva especie."

Comments from Silva: "YES.  T. divisorius is a good species."