Split (A) Grallaricula cumanensis and (B) G. kukenamensis from G. nana
Proposal (421) to South American
Classification Committee
Effect of Proposal: A Yes vote on both
parts of this proposal would result in a split of Grallaricula nana into three species.
Discussion:
Donegan (2008) studied plumage, biometrics and voice
of Grallaricula nana in connection
with the description of two new Andean subspecies in the group. Given that such a wealth of data became
available in the course of this project, species limits were also
considered. The methods for
determining species limits are similar to those applied by Isler et al. to
assess antbird species limits.
Taxa were recommended for species rank where vocal, biometric and
plumage differences were equivalent to those between sympatric Grallaricula species. (A study of
vocal differences between a sample of various sympatric or parapatric Grallaricula species pairs showed at
least three diagnostic differences in song, in the studied variables, to
exist.) The split species would be
(i) G. nana, a widespread tropical
Andean species; (ii) G. cumanensis of
the Sucre peninsula and Paria Mountains of Venezuela; (iii) G. kukenamensis of the tepuis. These three taxonomic groups postulated
for species rank are each separated by 200-350 km of unsuitable lowland habitat
and are restricted to well-known endemic regions. The distances between these populations are likely to prove
substantial for terrestrial, montane birds with poor flight such as Grallaricula.
G. cumanensis ("Sucre
Antpitta") of the Paria and Caripe mountains of Venezuela (including
subspecies pariae) differs vocally
from G. nana (subspecies: nana, occidentalis, hallsi subsp.
nov., nanitaea subsp. nov. and olivascens) in both its song and
call. The differences are
equivalent to, and, in the case of call, greater than, differences between
sympatric or parapatric Grallaricula
species. Three such differences
were shown between each of cumanensis
group, nana group and kukenamensis. The call of the cumanensis
group is also very different from other G.
nana. Bob Planque in an online
article (http://www.xeno-canto.org/features.php?action=view&blognr=1) recently
considered the call of this taxon to be unique, not only within G. nana but also within the genus Grallaricula. G. cumanensis also
shows substantial differences in biometrics and bill morphology from all other members
of the G. nana group. Ridgely & Tudor (1994) had
previously noted that this population likely should be treated as a different
species based on its call, song and plumage.
The biometrics and plumage of the disjunct
population G. kukenamensis ("Guianan
Antpitta") of the tepuis are diagnosably distinct, as for G. cumanensis. Turning to voice, a single recording 80% identified as G. kukenamensis (Boesman 2003) was the
only one available. A number of
regional experts were consulted on this recording and everyone seemed to agree
that there was nothing else it could be.
This recording differs from G.
nana and G. cumanensis to the
same extent as sympatric or parapatric Grallaricula
species, being much longer in length and having a note-shape more like Hooded
Antpitta G. cucullata. Again, three diagnostic differences in
song were found both with respect to the cumanensis
group and nana group, applying
various highly conservative assumptions about the available recording. Further details of the statistical
tests involved are set out in Donegan (2008). Further personal communications suggest that this population
has a further, distinctive call but recordings of this other call were not
available for the study.
Hopefully, those recordings can be published in due course but that
should not prevent a decision being made available based on the available
data. In any event, the treatment
of kukenamensis as a species is
supported by diagnostic biometric differences, based on a good sample of
specimens for all taxa, as well as notable differences in bill morphology
(illustrated in Donegan 2008) and plumage.
For committee members who are strongly wed to
status quo treatments and Peters or who otherwise typically reject my proposals
for whatever reason, one could at a stretch reject this proposal on the basis
that a better and more certain vocal sample for kukenamensis is needed.
Such an approach would in my view represent a missed opportunity. Additional vocal data for this
particular population would be welcome.
However, the split of kukenamensis
is strongly supported by other data in addition to voice. Furthermore, if cumanensis is split, a step which is strongly supported, then it
would be difficult to recommend which of nana
or cumanensis the taxon kukenamensis should be placed in, given
that it is different from both in biometrics (more similar to cumanensis), bill morphology (not closer
to either), plumage (more similar to nana),
as well as in voice (apparently not closer to either) and it is the most geographically
isolated of all three proposed species groups. One might also argue that molecular data would be helpful,
which is also true. However, the
three populations postulated for species rank are all fully diagnosable by
measures from multiple sources (plumage, voice, biometrics, bill morphology) so
must be genetically different in some way, at least mutually monophyletic on
some of the genes that code for plumage, voice, biometrics and bill morphology,
one supposes. SACC has recently
accepted splits in other groups without molecular data, e.g. the recent Momotus proposal. A discussion of other approaches is set
out in Donegan (2008) but none of them are recommended.
The differences between each of the three G. nana groups, together with full data on
biometrics and vocal variables, are set out in some gory detail, subspecies by
subspecies, in the appendices to the paper. (Please note that an erratum
was published in the next issue of Bull BOC to correct errors in the legends
for one of the recordings and one of the specimen images in the paper.)
The proposed three-way split of G. nana is itself a conservative
approach. The "G. nana group" (after cumanensis and kukenamensis are split) itself comprises at least 4 phylogenetic
species (fully diagnosable, allopatric populations with small
differences). Authorities that
adopt other species concepts might split wish to split it further. However, such approaches were not
proposed by Donegan (2008) nor are they proposed here, because differences
between phylogenetic species in the nana
group (as redefined) are not equivalent to those between sympatric Grallaricula species.
English Names:
The names "Sucre Antpitta" for G. cumanensis and "Guianan
Antpitta" for G. kukenamensis
were proposed. Paria Antpitta
was previously suggested by Ridgely & Tudor (1994) for cumanensis, but this appears to be based on the subspecies name pariae, which is junior, and the cumanensis group has a wider range than
the Paria peninsula, being near-endemic to Sucre department. This proposal is provisionally to adopt
the names suggested by Donegan (2008).
However, if this proposal passes, I will raise a separate proposal on
the English name for cumanensis.
Reference:
Donegan, TM. 2008. Geographical variation in
Slate-crowned Antpitta Grallaricula nana,
with descriptions of two subspecies, from Colombia and Venezuela. Bull Brit. Orn. Club. 128(3): 150-178.
Other references cited therein.
I have also added a discussion of G. nana recordings on xeno-canto which
does not include sonograms of recordings for all taxa but which may be helpful
to committee members:
http://www.xeno-canto.org/features.php?blognr=34&action=view
Recommendation: A Yes vote,
to split this species into three for the reasons set out above. To accommodate potential differences in
voting on the cumanensis group and on
kukenamensis, consider the former to
be part A and the latter part B of this proposal.
Thomas Donegan,
March 2010.
Comments from Robbins:
A = YES. I do support recognizing cumanensis/pariae
as a species separate from other nana based on the relatively pronounced
vocal and plumage differences.
B = NO. Given the lack of definitive song and whether described
calls are truly analogous (hopefully the reference in Donegan [2008] to an
upcoming paper by D. Ascanio will clarify this), it would be premature to
elevate kukenamensis to species level. Obviously, genetic data would further clarify relationships
in this group.
Comments from Remsen: A =
YES. Evidence for splitting cumanensis is strong.
B = NO. I would hold off on kukenamensis until
comparable vocal data are obtained.
That kukenamensis is
diagnosable in terms of plumage and morphology to the same degree as cumanensis is from nana is suggestive.
Its not a lot to ask to wait for a few more recordings of unequivocal kukenamensis. This is not a stretch, contra the proposal, but a logical
position given the disparity in data quality.
The
proposal portrays a NO vote as indicating strongly wed to status quo
treatments and Peters or who otherwise typically reject my proposals for
whatever reason. First, I suspect
there is no group of 10 people more aware of the shortcomings of the status
quo, whether Peters or otherwise, than those on SACC, all of whom are keenly
aware that status quo species limits in Neotropical birds badly under-represent
true species-level diversity under a BSC framework. If it were up to us as individuals to realign current
taxonomy to reflect what we know or suspect is the case based on vocal
differences without publishing the documentation, then we could add hundreds of
species overnight. It is often
frustrating and certainly time-consuming to have to go through the process of
publication. Nonetheless, rather
than being wedded to status quo, what we ARE wedded to is a process of change
than involves a degree of rigor that was missing from the
extinction-by-penstroke approach to species limits by Peters, Hellmayr, and
others, namely publishing data and explicit rationale for change. To do otherwise only repeats the
philosophical mistakes of the Peters era by perpetuating low standards for
change. Im sure Peters and his
soul mates were just as convinced that their decisions were correct as we are
convinced that our own, unpublished views are correct. As for Donegans implication that votes
against some of his proposals are rejected ad hominem, that 27 have passed
suggests that this perception is unwarranted; and most of those that have
failed are proposals on English names, hyphens, or status of introduced species
that represent differences in taste or philosophy.
Additional comments from Donegan: Those
who have voted have an interesting concept of the scientific rigour of
different publications. Peters and
Hellmayr did an excellent job in formulating a rational and consistent taxonomy
for a large number of species based on the data available to them. However, it is worth comparing their
material and methods with those adopted here and in other recent studies. Peters, Hellmayr and others of their
age based their taxonomies on studies of a few collections they were able to
visit and on hand-written notes of specimens in different museums (possibly
aided by black-and-white photography).
Their compendia treated large numbers of taxa, so attention to any one
species was probably limited to a few days at most, probably more often a few
hours. Only a handful of specimens
were studied by Hellmayr (1917) in the case of Grallaricula nana, many of which had vague locality data (e.g.
Bogota, East Ecuador). There
many substantial distributional gaps in the specimen record compared to what we
have now; and no data on voice was available.
With this group in particular, Hellmayr essentially concluded that the material available to him was inadequate to assess the status of many populations, such as those in the Venezuelan Andes (see passages quoted in Donegan 2008). Peters did not have much to say about this group and simply followed earlier treatments. Since Hellmayr (1917), five subspecies, as well as a host of major range extensions for described populations, have been discovered / described. In Donegan (2008), I measured over 150 G. nana specimens, the vast majority of which had good locality data. I collated data on approximately a hundred more specimens (through inspecting them or photographs), studied 224 sound recordings and applied a series of statistical tests to analyse the diagnosability of all known populations based on 6 biometric, 8 vocal and various plumage variables as well as bill morphology against various postulates tests for species and subspecies rank. Some fieldwork was carried out in Colombia. GIS analysis was carried out to map distributions of each subspecies based on these data and data from other sources (photographs, sound recordings, other specimens). The study was pretty exhaustive of available (non-molecular) resources and took 3 and a half years to complete from its inception to publication. I fail to see where the scientific rigour is in rejecting the conclusions of this in-depth study in favour of a treatment suggested almost 100 years ago, based on a small fraction of the material available today and only some of the subspecies known today; or in favour of the recommendation of a footnote by Ridgley in a field guide.
A short note on the other calls of kukenamensis would be helpful, but based on personal communications, such a note would seem likely only to support the taxonomic recommendations in Donegan (2008), which were reached independently. It would also be nice to have a molecular study, but I dont see that being used as a reason to reject other proposals based on studies using traditional methods.
Its moderately comforting that there have been positive comments on splitting cumanensis. Ridgley & Tudor (1994) thought that should be split too, so adopting such an approach does not require a view to be taken on the merits of Donegan (2008). I have asked Van Remsen to split this proposal into part A to split cumanensis; with Part B to split kukenamensis. The first option would be somewhat a case of two steps forward, one step back and result in a species with a bizarre, possibly unique, distribution that may be paraphyletic. However, the resulting treatment is likely to be less paraphyletic and less offensive to the BSC than the current treatment and, as a result, it would be an improvement compared to doing nothing.
(A PDF of the paper has been posted (unauthorised) on line. If anyone wants to see a PDF of the short erratum, please let me know.)
http://www.scricciolo.com/Nuovo_Neornithes/Grallaricula%20nana%20Bull%20BOC%20Donegan.pdf
Response from
Remsen: It doesnt matter how many specimens
youve measured, what stats were used, etc., in terms of determining the taxon
rank of kukenamensis if those data do not include the data critical to assigning species limits. That kukenamensis is a
diagnosable unit was never disputed as far as I know. Donegans data show conclusively, much more so than
Hellmayr-Peters, that kukenamensis is a valid taxonomic unit, i.e.,
should be ranked at least as a subspecies under BSC. [A paper I have in press proposes that properly described
subspecies in the BSC are equivalent to PSC species.] Your best argument for species rank for kukenamensis
is that including it in nana might
make that species paraphyletic with respect to cumanensis, but we wont know that for use until we have genetic
data. As for species rank for kukenamensis,
the proposal sates: Turning to
voice, a single recording 80% identified as G. kukenamensis (Boesman 2003) was the only one available. Donegan, Im sure, would support vocal
comparisons as the best way rank allopatric populations in terms of species vs.
subspecies. So, how then can
Donegan consider it rigorous to change the rank of kukenamensis based on one recording of
uncertain identification?????
As
for molecular data and whether this is required to make such a decision, many
are under the spell of the widespread misconception that molecular data solve
ranking of allopatric populations; in other words, all we might need to assign
species rank is sequence data on a couple of genes to measure whether its a
species or subspecies. This is
incorrect. Genetic distance among
known good species is as low as 0% (Galapagos finches), whereas genetic
distances among populations that do not differ in any phenotypic way ranges up to
11% (Ben Marks dissertation). Even
within a closely related group of birds, say the nana complex, genetic
distance probably is the best predictor of time-since-isolation, but it is also
influenced by things like effective population size (all else being equal a
small population would differentiate more rapidly than a large one); further,
the genes used are explicitly assumed to be neutral, i.e., unrelated to
something relevant to reproductive isolation.
As
for Donegans point that not ranking kukenamensis as a species retaining kukenamensis in nana until we have more data would result in a species with a bizarre, possibly
unique, distribution that may be paraphyletic, this evidently refers to a
distribution that would place a tepui bird with nana is in the Venezuelan Andes rather than the geographically
closer cumanensis in the Coast
Range. However, note that mostly
Andean Doryfera johannae has a tepui
subspecies without even a representative in the Venezuelan Andes much less
Coastal Range. At least G. nana is present in the Venezuelan
Andes (nominate nana). Similarly, Aulacorhynchus derbianus has two endemic subspecies in the tepuis
but has no representative in either the Venezuelan Andes or Coastal Range. Macroagelaius
has a similar distribution:
Colombian Andes + tepuis.
The point is that tepui species closest relatives do not necessarily
occur in the Coastal Range or even the Venezuelan Andes. So, the distribution pattern created by
including kukenamensis in nana
is not bizarre. Whether it is
unique or not would depend on having sufficient N of species with populations
in all three places (Andes, Coastal Range, and Tepuis) and finding that in no
other case was the Andean taxon sister to the Tepui taxon.
Comments from Stiles: YES for recognizing cumanensis and for calling it Sucre Antpitta. For now, I vote NO on recognizing kukemanensis, pending a better analysis of vocalizations: that given for the Pseudocolopteryx citreola proposal should serve as a model for such cases. It seems a bit unrealistic to call this a missed opportunity when the evidence is incomplete – its really a golden opportunity for someone to do it right, now that attention has been called to this case.
Comments from Nores:
A = YES. Yo estoy de acuerdo en reconocer cumanensis/pariae como una especie separada de nana, ya que tiene importantes diferencias en coloracin y
vocalizaciones.
B= NO. No me parece apropiado
elevar a kukenamensis a nivel de especie ya que las diferencias en
vocalizacin sugeridas no son lo suficientemente seguras como para tomar esta
desicin. Generalmente las subespecies tienen diferencias biomtricas con la
tpica y no es razn para considerarlas especies. Prefiero esperar hasta que
haya grabaciones seguras de kukenamensis o anlisis moleculares que
apoyen esta separacin.
Comments from Stotz:
A = YES.
B = NO. I believe it likely
that kukenamensis is a good
biological species, but the equivocal vocal evidence makes it hard for me to
vote to recognize it at this point. What does it mean that a recording is 80% certain that it
belongs to a particular taxon? The
plumage resemblance for kukenamensis
to nana makes me comfortable leaving
it in nana for the time being.
Comments
from Cadena:
A=YES
B=NO, for reasons clearly stated by Remsen.
Donegan's paper is a nice piece involving careful study of museum specimens,
some of which were collected by the author himself.
Comments from Zimmer:
A=YES. Donegan has done a nice job of using
multiple data sets to support such a split.
B = NO. I have little doubt, based on the evidence presented by
Donegan, and, on having listened to a recording, apparently of kukenamensis, by David Ascanio, that kukenamensis is a valid species. Such a treatment would also make the
most sense on biogeographic grounds alone. However, much as I would like to, I cant see basing any
kind of change on the single recording used in Donegans study. If the recordist and the author cant
vouch for the accuracy of the identity of the bird in the recording, then how
can we be expected to take it as certain?
Donegan has focused the spotlight on a previously overlooked situation,
and I look forward to someone now coming through with the hard data that will
allow us to make the change in our taxonomy.
Comments from Pacheco:
A=[Yes] As evidncias
reunidas remetem separao de cumamensis.
B= [No] Ainda que considere a possibilidade de kukenamensis
provar ser entidade independente de nana num futuro prximo, voto
– considerando o rigor desejvel – pela manuteno do status atual
at que amostras incontestes do repertrio vocal possam ser analisadas.