Proposal (327) to South American Classification Committee

 

Elevate subspecies veraepacis, stenorhyncha, olivacea, aenea, amazona, and turdina of the Thrush-like Schiffornis (Schiffornis turdina) to species rank

 

Effect on SACL: This change would add 5 new species to the list.

 

Background: The Thrush-like Schiffornis (Schiffornis turdina) is a variable species, currently represented 13 subspecies (Peters 1979; Ridgely and Tudor 1994; Snow 2004). Recent evidence based on molecular mitochondrial markers indicates 7 distinct lineages (Nyári 2007). Based on both molecular and vocal characters, and the respective geographic extents of each lineage, a revised species limit and taxonomy is proposed. The recommendations outlined below are to be viewed as representative of the geographic sampling undertaken by the molecular study of Nyári (2007), while further studies will be needed to refine species limits of several populations, especially in the Amazon Basin.

 

For each newly proposed species, I have retained the English names following Hellmayr (1929). The only exception is S. aenea, for which I propose the name Foothill Schiffornis, to reflect the distinct habitat of this particular population, tied to the Eastern Andean foothills.

 

1. Schiffornis veraepacis Brown Schiffornis - would encompass populations currently attributed to the subspecies veraepacis, dumicola, acrolophites, and rosenbergi. There appears to be little genetic and vocal distinction between these populations, hence the recognition of a single species is warranted.

 

2. Schiffornis stenorhyncha Slender-billed Schiffornis - although not sampled directly in the genetic analysis, vocalizations of this subspecies and sampled panamensis from eastern Panama are virtually indistinguishable. These two forms also appear to have a more rufescent plumage hue.

 

3. Schiffornis olivacea Olivaceous Schiffornis - the recognition of this species is warranted due to the genetic distinctiveness of this group. Although not as distinct vocally from the similar two-noted S. veraepacis, this taxon was very well supported as a cohesive monophyletic group, containing samples north of the Amazon River, previously attributed to the subspecies olivacea, amazona, and wallacii. The retention of olivacea over wallacei (with the latter having nomenclatural priority) is recommended due to the uncertainties associated with the location of the type of wallacii. It was designated as having been collected in Brazil, Pará, without reference as to which bank of the Amazon River. Moreover, the geographic extent of the wallacii-like forms has been problematic (Peters, 1979).

 

4. Schiffornis aenea Foothill Schiffornis - a very well defined population both genetically and vocally, occurring in the foothills of the eastern Andes in Ecuador and Peru.

 

5. Schiffornis amazona Amazonian Schiffornis - based on limited genetic sampling, this species would include populations from the western Amazon Basin, currently attributed to the subspecies amazona and steinbachi.

 

6. Schiffornis turdina Thrush-like Schiffornis - because of limited sampling throughout this extensive geographic area, the retention of the nominate subspecies for the group is appropriate and would include populations from the southeastern Amazon Basin (amazona) and the Atlantic Forest (turdina).

 

It should be noted that while the phylogeographic patterns based on molecular and vocal analyses carried out by Nyári (2007) included the whole geographic extent of Schiffornis turdina complex, a number of key areas still need to be sampled. These areas are directly tied to the proper specific delimitation of S. amazona and S. turdina, as proposed herein. Even by looking at the tree topology outlined in Fig.2 in Nyári (2007), it is apparent that further subdivisions of Amazonian clades 5 and 6 may be warranted.

 

Recommendations: Based on the above delimitations (following Nyári 2007) and from the long recognized vocal differences within Schiffornis turdina complex, I recommend the adoption of these new species. A "YES" vote would recognize all changes as outlined above.

 

References:

Hellmayr, C.E., 1929. Catalogue of bird of the Americas. Field Muse. Of Nat. Hist. Publ. Zool., Series 13, Part VI. Chicago, USA.

Nyári, Á. S. 2007. Phylogeographic patterns, molecular and vocal differentiation, and species limits in Schiffornis turdina (Aves). Molecular Phylogenetics and Evolution 44: 154-164.

Peters, J.L. 1979. Check-list of Birds of the World, Vol. 8. Museum of Comparative Zoology, Cambridge, Massachusetts.

Ridgely, R.S., Tudor, G. 1994. The Birds of South America, Vol. 2: The Suboscine Passerines. University of Texas Press, Austin, TX.

Snow, D.W. 2004. Family Pipridae (manakins). Pp. 110-169 in: del Hoyo, J., Elliot, A., and Christie, D.A. eds. (2004). Handbook of the Birds of the World. Vol. 9. Cotingas to Pipits and Wagtails. Lynx Edicions, Barcelona.

 

Arpad Nyári, January 2008

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Comments from Stiles: "I will wait on this one for more input from committee members. I am particularly intrigued by the fact that Nyári's proposal would place members of the "subspecies" amazona in three different species! Also, I am fairly amazed that Nyári apparently never made morphological comparisons among his proponed species (at least, he never mentioned them in his paper). While all "Schiffornis turdina" look pretty much alike, I'd be surprised if detailed measurements or colorimetric comparisons did not turn up some useful characters - as they have even among the notorious Scytalopus! I suspect that a fair number of specimens of all forms are available - they get caught in mist nets rather frequently, in my experience."

 

Comments from Cadena: "NO. Although clearly S. turdina comprises more than one species, this is a difficult case that I don't think has been resolved satisfactorily. The one thing that strikes me the most is that Nyári apparently sees no problem with recognizing polyphyletic species. For example, his proposed species S. veraepacis as delimited in the paper includes the phylogroup that is sister to a clade formed by all other populations of S. turdina and only two of the populations that compose one of the two well-supported groups within the latter clade (i.e. the geographically distant phylogroups 1, 3, and 7). I actually see no problem with the recognition of paraphyletic species under the BSC (this is the expected outcome of speciation via peripheral isolates), but the rationale for this treatment in the case of Schiffornis is not clear in his paper or in the proposal. The voices do seem similar in the simplified spectrograms presented in the paper, but as the author states, his assessments of vocal variation are not detailed nor quantitative; I wonder if closer inspection might reveal vocal differences that are important for species recognition, and whether this might lead to further subdivision that does not require recognizing non-monophyletic taxa.

 

"Another issue that makes me worry a little is that no Colombian populations were included in the molecular analyses, and the only Colombian recording considered in the vocal analyses is from east of the Andes (i.e. there is no representative from the Magdalena Valley, the Cauca Valley, the northern lowlands, the Chocó, etc.). Based on what we are learning about the complexity of patterns of differentiation and the affinities of Colombian populations of other birds, I'm not sure one can safely say to which of the species under the proposed new classification would one assign Colombian birds."

 

"In sum, the data are suggestive, but the current study is still not quite as detailed as one would like to sort this out clearly. We really need more studies before the proposed taxonomic changes can be adopted".

 

Comments from Zimmer: "NO. There is insufficient evidence at present to make this split."

 

Comments from Robbins: "YES. This study documents what a number of us have appreciated for ca. 30 years, that there are multiple species in what is currently recognized as a single species. Nyari's study is a major step forward in understanding species limits within the turdina complex. As the author clearly points out, further sampling (both vocal and genetic) is needed in a few areas, but that does not denigrate the fact that at least six species, regardless of one's species definition, should now be recognized.

 

"Note that I state there are at least six species, whereas Nyari, because of superficial similarities in the primary vocalization between Guiana Shield populations and Mexico and Central America, took a conservative approach (strict BSC definition) and recommended the recognition of only 5 species. Given the 9.6 % sequence difference between Guianan and Central American birds (not only is this the greatest genetic difference between any pair of taxa, but it is greater than either is to virescens, a taxon that has been traditionally recognized as a species - indeed, we currently recognize it as a species), that they should be treated as species.

 

"I would proffer that had Nyari had reasonable sample sizes of vocalizations that he would have found consistent differences between these non-sister taxa. I consider it analogous to what we see in pygmy-owls (Glaucidium), there are just so many ways that one can modify a simple 2-3 noted whistle within a clade, like we see in Schiffornis. For example, the endemic northeastern Mexican Glaucidium sanchezi has a primary vocalization that is very similar to the endemic southeastern Brazil birds (minutissimum). They are not sister taxa and I don't think anyone would suggest that they should be treated as the same species. Obviously, there are two or three explanations for why these pygmy-owls might now have very similar vocalizations (as we see among highly genetically differentiated Schiffornis taxa). In sum, the lack of striking vocal differences between Guiana and Central American birds does not come as a surprise. If we are going to be consistent in our treatment of Schiffornis, it is straightforward decision to recognize six species at this point in time.

 

"Re Gary's comments: Nyari was well aware of the subtle plumage differences among Schiffornis taxa as detailed by Hellmayr (1929), but rehashing such minor differences added nothing to this study and was beyond the scope of a journal such as MPE. Indeed, subtle plumage differences described in the days of yore are what have held us to an archaic, single species treatment. The current study has shed considerable light on species limits within this complex."

 

Comments from Jaramillo: "YES - It is clear from the work of Nyari, and from traveling around in the Neotropics that there is more than one species in turdina. I was originally troubled as I thought that clades 3 and 1 were being proposed as separate species although they are similar genetically and vocally. These two clades are geographically separated, and that is odd, but they are best kept as one species in this proposal and I think that is prudent at least until there is more data. There are some unresolved issues here, and surely there will be further re-arrangement in the future, but as it stands this is an improved organization of this group than keeping the status quo. I am not troubled by the vocal similarity of veraepacis and olivacea, particularly given the genetic data that separates them.

"However, I do not think that turdina sensu stricto should be called Thrush-like Manakin, let's leave that English name for the entire group and make something else up for that entity. I think it is particularly confusing in this case where one species may be separated into so many."

 

Additional comments from Stiles: "NO. In this case I agree with Daniel - Nyari's data are very interesting and certainly suggestive, but at this point there are just too many holes.. including the lack of data for Colombia, where at least three of his putative species should occur and where zones of contact might occur in some cases, also the lack of any statistical analysis of vocalizations and the complete absence of any morphological analysis. As I suggested, it would be surprising if modern colorimetric methods and statistics were unable to add something more convincing.. regarding Mark's comments, none of these methods were available to Hellmayr, so simply discounting morphology based upon Hellmayr's difficulties doesn't convince me. Splitting what was one subspecies (amazona) into three species would also seem to require a bit more in the way of data.. at some point one would have to be able to diagnose these based upon more than distribution. As we all know, the relation between genotype (and this based upon a few genes out of thousands) and phenotype (color, vocalizations, biometrics, behavior - in short, what the birds perceive) need not be simple. What we have in Nyari`s work is a broad-brush phylogeography of the Schiffornis complex, tying some geographic segments of the complex to possible divergence times - but with the possibility that other genes might present rather different results. This in itself is useful, but I would question whether taxonomic changes are justified on this basis alone. At least in Colombia, specimens and recordings are available for several forms and should be used, and I suspect that there are plenty of data in museums etc. in other countries down this way - so, for the moment, while acknowledging that Nyari's study is suggestive, I await a more comprehensive analysis before feeling comfortable with this split."

 

Comments from Pacheco: "NO. Na minha avaliaćčo faltou ao trabalho uma interaćčo melhor resolvida entre as análises genéticas e os dados morfológicos e vocais, além da ausźncia sensível de amostragem de alguns dos táxons implicados. Como bem colocou Stiles há uma imensa quantidade de informaćões já disponíveis que foi negligenciada. Penso que o trabalho de Nyari indica alguns “caminhos”, mas nčo resolveu satisfatoriamente toda a trama."

 

Comments from Stotz: "NO. I am very sympathetic to the idea that Schiffornis turdina consists of multiple species. The paper by Nyari is an important contribution to our understanding of the species complex, but I find I can't endorse the taxonomic conclusions. My concerns are several. The paper uses genetic analysis and vocalizations to delimit groups. The problem is the datasets are not concordant. Then to compound that, in some cases the authors seem to treat the genetic relationships as most important and in other cases the vocal data as most important.

 

"So, clades 1, 3 and 7 (Central America, western Ecuador, and Guianan Shield) are treated as one species (veraepacis) because of very similar voices, despite the fact that genetically the Guianan Shield populations are basal to all of turdina (sensu lato). Additionally this group is hard to accept geographically as well. In contrast, amazona and turdina are defined by genetic grouping, but populations within his turdina clade are within song group C, which is basically amazona, different from song group D, which is eastern Brazil turdina.

 

"A further problem is that big areas of western Amazonia and the east slope of the Andes are not included in either the genetic or vocal data base. Where do they go? It doesn't seem like you can use plumage to place them, so what do we do with them. With these issues unresolved, I can't vote for this treatment."

 

Comments from Remsen: "NO. I was going to vote YES on this on the basis that any treatment is better than continuing to treat this as a single species, but then Doug's comments convinced me otherwise. Nyári's work is an important first step, and hopefully he will do some follow-up so we can get rid of the misleading single-species treatment."