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
______________________________________________________________________________________________________
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 avaliação faltou ao trabalho uma interação
melhor resolvida entre as análises genéticas e os dados morfológicos e vocais,
além da ausência sensível de amostragem de alguns dos táxons implicados. Como
bem colocou Stiles há uma imensa quantidade de informações já disponíveis que
foi negligenciada. Penso que o trabalho de Nyari indica alguns “caminhos”, mas
não 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."