Proposal (127) to South American Classification Committee

Split Thryothorus mystacalis from T. genibarbis

Effect on South American CL: This would elevate a taxon to species rank that that we treat as a subspecies of a species on our list.

Background: The montane mystacalis group was formerly (e.g., Hellmayr 1934) regarded as a separate species from the Amazonian genibarbis group, but they were treated as conspecific without comment by Paynter & Vaurie (1960). I suspect that his reasoning was based on the fact that the closest subspecies of lowland genibarbis geographically to the allopatric mystacalis group is also the grayest-breasted of the lowland group (juruanus). There is also a possibility that the northern forms of mystacalis, such as consobrinus (as illustrated in Hilty 2003), are more like lowland genibarbis than are the southern mystacalis forms.

"New" information: Paynter's treatment has been followed by subsequent authors (e.g., Meyer de Schauensee 1970, Parker et al. 1982, Hilty & Brown 1986) until Ridgely & Tudor (1989) re-elevated the mystacalis group to species rank. This was then followed by Sibley & Monroe (1990), Brewer (2001), Ridgely & Greenfield (2001), and Hilty (2003), but not by Fjeldså & Krabbe (1990) or Dickinson (2003).

The mystacalis group differs from the Amazonian group in several minor aspects of plumage, but the most noticeable is a fairly strong difference in color of the underparts (gray in mystacalis, tawny in genibarbis). The difference in size is impressive, with lowland genibarbis roughly the size of T. coraya and highland mystacalis the size of T. euophrys. In fact, the plumage similarities (lack of barring in euophrys aside) and mainly allopatric distribution of mystacalis and T. euophrys hints that they may be more closely related than either is to lowland genibarbis (and the partly allopatric distributions and plumage similarities of lowland genibarbis and T. coraya hints that they may also be sister species relative to mystacalis). On the other hand, my assessment (and Bob's?) of the differences may be biased by the southernmost member of the mystacalis group, nominate mystacalis, the only one represented here at LSU; perhaps the northern taxa are more similar.

Ridgely & Tudor (1989) described the voice of lowland genibarbis as "more like that of Coraya Wren than the slower, rich, mellow gurgling of Whiskered Wren." [Note again the similarity of genibarbis and coraya.] Brewer (2001) essentially repeats the description in Ridgely & Tudor (1989). I suspect that both are presented on a "Hardy" cassette somewhere, but no formal analysis has been published.

Analysis: There's not much to analyze, but it seems to me that there are plenty of reasons to keep mystacalis as a separate species and few to unite it with mystacalis. Published information for the split is weak, but there is nothing in print that I know of to support Paynter's original lump. The qualitative descriptions of voice strongly suggest that two species are involved.

There is a possibility that the case might not be so simple if northern taxa in the mystacalis group were included in these assessments (although Hilty 2003 did follow Ridgely), but with the Ecuadorean taxon being the nominate form, recognition of mystacalis as a species per se would not be crippled by northern complications. However, see message below from Daniel Cadena.

Recommendation: Although I am usually a conservative on overturning Meyer de Schauensee classification without a decent published analysis, in this case the rationale for the original lump is essentially nonexistent and is so easily trumped by the meager published evidence for the split that I would recommend a YES on this one. In my opinion, the burden-of-proof ought to be on the conspecific treatment. Above all else, however, is my concern that our presently constituted genibarbis is not a monophyletic group with respect to euophrys and coraya.

Literature Cited (partial):

BREWER, D. 2001. Wrens, dippers, and thrashers. Yale University Press, New Haven.

FJELDSÅ, J., AND N. KRABBE. 1990. Birds of the High Andes. Zoological Museum, Univ. Copenhagen, Copenhagen, Denmark.

HILTY, S. L. 2003. Birds of Venezuela. Princeton University Press, Princeton, New Jersey.

HILTY, S. L., AND W. L. BROWN. 1986. A guide to the birds of Colombia. Princeton University Press, Princeton, New Jersey.

MEYER DE SCHAUENSEE, R. 1970. A guide to the birds of South America. Livingston Publishing Co., Wynnewood, Pennsylvania.

PARKER, T. A. III, S. A. PARKER, & M. A. PLENGE. 1982. An annotated list of Peruvian birds. Buteo Books.

PAYNTER, R. A., JR., AND C. VAURIE. 1960. Family Troglodytidae. Pp. 379-440 in "Check-list of birds of the World, Vol. 9" (Mayr, E., and J. C. Greenway, Jr., eds.). Museum of Comparative Zoology, Cambridge, Massachusetts.

RIDGELY , R. S., AND P. J. GREENFIELD. 2001. The birds of Ecuador. Cornell University Press, Ithaca, New York.

SIBLEY, C. G., AND B. L. MONROE, JR. 1990. Distribution and taxonomy of birds of the World. Yale University Press, New Haven, Connecticut.

Van Remsen, August 2004

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Comments from Daniel Cadena: "I just saw the new proposal you posted on the SACC site regarding species status for T. mystacalis, and the concern you noted regarding lack of information on northern forms. If I may contribute a bit of information, I am familiar with "T. genibarbis" from the East and West Andes of Colombia, and was struck when I heard what people told me was the same species in Amazonian Peru, as they indeed sound completely different. I have some tape recordings from Colombia I could send you if you are interested."

Comments from Stiles: [YES] "Regarding splitting mystacalis, here is one of these cases where having field experience helps. I am quite familiar with the mystacalis group on both sides of the E Andes in Colombia, and not long ago met genibarbis in W Brazil. Like Daniel, I thought I was hearing a slightly unusual coraya until I captured one and had its mate roaring at me a few meters away. Hence, I have no doubt that the split is well justified - and my experience corroborates the notion that the lowland genibarbis may well be more closely related to coraya than to mystacalis. Given that the published evidence for the lump is scanty at best, I will vote YES here."

Comments from Robbins: " I vote "YES" to elevate Thryothorus mystacalis from T. genibarbis based on Ridgely and Tudor's, Cadena's, and Stiles's comments on differences in vocalizations."

Comments from Nores: "YES. Para especies tan parecidas, diferencias en color, tamaño y canto justifican, a mi modo de ver, plenamente la separación."

Comments from Silva: "YES. Let us keep the original proposal. In general, I have seen two recurrent types of taxonomic questions. The first is when the taxon was described as a separated species and afterwards it was merged (without any published and adequate analysis) as a subspecies within a widespread taxon. The second case is when the taxon was described as a subspecies of a widespread species, and someone proposed to rank it as full biological species without an adequate analysis. I think the first case is very easy to solve, and we should be conservative and restore the original proposal if there is evidence supporting this. In the second case, we should ask a more adequate and published analysis to change the species status. I think if we apply this rule consistently, we can make the decision process a bit smoother."

Comments from Zimmer: "I vote "YES". I know this bird from N Venezuela, and the vocal distinctions from genibarbis are striking. Jose Maria makes a good distinction regarding the level of published evidence that we require for cases such as this, in which the original lump was done without published justification."

Comments from Pacheco: "[Yes] Acompanhando o senso comum. Concordo com a racionália apresentada por Silva, como critério aceitável. Não há porque esperar por análises publicadas se o tratamento vigente e inapropriado (diante das evidências disponíveis) é que foi implementado, por uma alguma obra, mesmo que importante, sem qualquer comentário/justificativa."

Comments from Jaramillo: "YES. I realize this has passed, but wanted to voice that I agree for the many reasons written."