Proposal (421) to South American
Classification Committee
Split
(A) Grallaricula cumanensis and (B) G.
kukenamensis from G. nana
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.
Anonymous,
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. It’s 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. I’m 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 Donegan’s 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 Anonymous: “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 don’t see that being used as a reason to reject other proposals
based on studies using traditional methods.
“It’s
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 Donegan
know.)
http://www.scricciolo.com/Nuovo_Neornithes/Grallaricula%20nana%20Bull%20BOC%20Donegan.pdf
Response
from Remsen: It
doesn’t matter how many specimens you’ve 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. Donegan’s 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 won’t 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.” Anonymous,
I’m sure, would support vocal comparisons as the best way rank allopatric
populations in terms of species vs. subspecies.
So, how then can Anonymous 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 it’s 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 Anonymous’ 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 – it’s
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 coloración y vocalizaciones.
“B = NO. No me parece apropiado elevar a kukenamensis a
nivel de especie ya que las diferencias en vocalización sugeridas no son lo
suficientemente seguras como para tomar esta decisión. Generalmente las
subespecies tienen diferencias biométricas con la típica y no es razón para
considerarlas especies. Prefiero esperar hasta que haya grabaciones seguras
de kukenamensis o análisis moleculares que apoyen esta
separación.”
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.”