Proposal
(478) to South
American Classification Committee
Species limits in Ortalis
(A) Split Ortalis
araucuan from O. guttata
(B) Split Ortalis
squamata from O. guttata
Effect of Proposal:
With the passing of
Proposal 43 9, Colombian Chachalaca Ortalis
columbiana was split from Speckled Chachalaca O. guttata. Many committee members stated in their
comments that they were in favour of taking further steps to split up this
group. In particular, many authorities
recognise the East Brazilian Chachalaca O. araucuan and the Scaled
Chachalaca O. squamata as separate species. This proposal gives committee members an
opportunity to consider the rank of these taxa.
History
of treatments:
There is no obvious status quo for these birds, with as many leading authorities
splitting these taxa as lumping them.
Important publications splitting them include Peters (1934), Sick (1993
- the leading ornithological reference work for Brazil for 2 and a half
decades) and the recent IOC list (Gills & Donker 2011 online). Vaurie (1965) appears to have been the person
first to propose the lumped treatment for the greater guttata group. Other
authorities such as Dickinson (2003), Rodriguez et al. (2005), Erize et al.
(2006), Brooks (2006) and SACC, among recent treatments, also adopted this
approach.
Some vocal data was
recently presented in Donegan et al. (2010).
That paper did not deal in detail with the status of these taxa (and a
much smaller sample was studied of them compared to columbiana) but some
sonograms were presented that may be of interest in considering this proposal.
Discussion of East Brazilian Chachalaca O. araucuan
1.
Plumage differences. O. araucuan
differs from O. guttata in being
white-bellied (not brown/buff-bellied), with ochraceous-cinnamon on the crown
and hind neck (not dark brown) and buffier on the undertail coverts. There is a nice illustration in the Erize et
al. (2006) non-passerines field guide of this one, alongside O. guttata.
2. Vocal
differences. As can be seen from the
sonograms in Donegan et al. (2010: bottom row, middle) and as discussed
therein, “Recordings of the northern
Brazilian populations araucuan examined are all of a three-syllable refrain.
Recordings had different relative lengths of the three syllables compared to
Amazonian populations (Figure 2).”
In the two inspected recordings of songs of this population, the second
note of the “Gua-cha-rac” refrain in the song is shorter than in other
populations, appearing as a downstroke rather than a blob of noise. That note is followed by a larger gap than
that which follows the second note in other populations, which means that the overall
rhythm sounds similar and song length is similar to guttata. However, there is a
clear difference in phraseology. These
differences are not as striking as those between O. columbiana and O. guttata, but available recordings can still be
easily told apart on sonograms.
Examples of songs of the guttata group are available on xeno-canto, together with a map
showing the distributions of the three groups (with araucuan top right):
http://www.xeno-canto.org/XCspeciesprofiles.php?species_nr2=430.52
Two examples of the araucuan song are available here:
http://www.xeno-canto.org/recording.php?XC=13415
http://www.xeno-canto.org/recording.php?XC=5634
3.
Biogeographic issues. The ranges
of O. guttata and O. araucuan are not continuous. O.
guttata is widespread from East Andean foothills to the Amazonian
region. O. araucuan has a highly disjunct distribution (separated by ca.
1300 km from guttata) and occurs in
northeasternmost Brazil only. Notably,
the range of Buff-browed Chachalaca Ortalis
superciliaris occurs in the region between the two. This sort of disjunct distribution pattern
(with another related species’ range bisecting them) is rather strange,
especially for a chachalaca. The entire
genus Ortalis can be regarded as a
giant superspecies (Sick 1993), but the lumping of these two looks most odd
under any arrangement where it is split up.
Discussion of Scaled Chachalaca O. squamata
1.
Plumage differences. O. squamata has a more brownish-cinnamon
hue on the cap and hind neck; and is greyer on the underparts than guttata.
It has been regarded as intermediate in plumage between O. guttata and O. araucuan (e.g. Erize et al. 2006).
2. Vocal
differences. The final note of the
Cha-cha-lac refrain in squamata is
lower pitched than the other two notes, whilst in both guttata and araucuan each
note tends to be of a more similar frequency.
We did not ascertain any obvious differences in phraseology between O. squamata and O. guttata in Donegan et al. (2010). Compare the sonogram on the left, last row of
Donegan et al. (2010) with the various O.
guttata sonograms therein. From what
I have seen from studying songs of other groups, like tapaculos and antbirds, I
would not consider this sort of a difference (in acoustic frequency of a single
note) to be as significant as those in phraseology shown by araucuan, but that is just a hunch, not
a reasoned or supported opinion. Either
way, the differences seem to be consistent; and there is a greater sample of squamata (compared to araucuan) available on xeno-canto and
other published recordings.
3.
Biogeographic issues. O. squamata occurs in the Atlantic
forest region of Brazil. Its
distribution is also disjunct from that of O.
guttata by a long distance (c. 1300 km) but no other Ortalis species’ range is interposed between them. The ranges of O. squamata and O. araucuan are
separated by some 1100 km.
Molecular studies
Molecular studies (e.g. Pereira et al. 2002,
Frank-Hoeflich et al. 2007) have not addressed the issue of relations between
members of the Ortalis guttata group
to date.
English names
O.
araucuan is often called “White-bellied
Chachalaca” (e.g. Sick 1993, Erize et al. 2006), but that name is pre-occupied
by O. leucogastra of Mexico and
Central America. The IOC uses “East
Brazilian Chachalaca” as a result. If
Proposal A passes, I would propose to use the IOC’s English name.
O. squamata is generally known as “Scaled Chachalaca”.
Recommendation
I am basically ambivalent about these two splits (as opposed
to that of O. columbiana which is
clear-cut). However, I have little field
experience with the Atlantic coast populations and would therefore welcome
further comments from committee members or others. The three postulated species in this group
clearly share many plumage features and have broadly similar voice. Nonetheless, populations are highly disjunct,
and there are diagnosable plumage and vocal differences.
Proposal A: O.
araucuan. On balance but with no great enthusiasm, I would support the
treatment of East Brazilian Chachalaca O.
araucuan as a separate species on the basis of its plumage differences,
vocal differences and biogeographic considerations (a “YES” vote).
Proposal B: O.
squamata. The plumage and vocal
differences from guttata are less
strong here, and the range of a combined guttata/squamata
does not so offend biogeographic ideals.
As a result, one cannot help but be even more ambivalent about this one
than the first. With even less
enthusiasm, I would on balance be inclined to accept this as a species on the
basis of plumage and vocal differences and the large range disjunction (which
are all symptomatic of long isolation).
This approach would be on the basis that accepting both these splits is
preferable to adopting some novel treatment; and also on the basis that this
split should be re-considered in the future as further data becomes available. (This is on the basis that the SACC should be
more open to changing its treatment where there are widely used alternative
taxonomies which sense in light of available data.)
Note:
Our recent Conservación
Colombiana paper did not really speak to the issues addressed in this
proposal in much detail, as they were outside scope. This proposal was produced only with a view
to helping your committee and presenting data relevant to a widespread
alternative treatment that is probably overdue for consideration. I look forward to seeing how this one goes
and to hearing any other people’s views.
Please don’t regard this as a position paper on splitting these species
– an issue the proposal author has no strong views on – and I would appreciate
it if committee members would not lay into the author accordingly!
References:
See the previous Ortalis proposal and SACC baseline.
Thomas
Donegan, January 2011
Comments from Stiles: “A very tentative NO: I would prefer to have a more thorough analysis of vocalizations and morphometrics and especially genetic data. I suspect that these two will eventually be split because the available data on plumage, vocalizations, and distributions are certainly suggestive.”
Comments from Robbins: “YES. In evaluating this proposal, I have attempted to put it in the context of criteria used in defining currently recognized Ortalis species. Virtually all the recognized species are based solely on differences in morphology (plumage pattern and coloration and soft part color and extent), i.e., no vocalizations and genetic data have been available in species status designations. In the current case, there are greater differences in plumage between guttata and araucuan (primarily head and neck coloration) than there are between other Ortalis taxa that are recognized as species. The biogeographic pattern also supports recognizing these as separate species. These aspects coupled with the vocal differences that Donegan has identified lead me to support this split. As I mentioned in my review of proposal 439, I would like to see genetic data brought to bear to help clarify relationships within this entire group, but given what we now have available and to be consistent with treatment of other taxa in this genus it seems best to recognize araucuan as a species. Finally, to be consistent with my evaluation of this proposal I now support the recognition of O. columbiana in proposal 439.”
Comments
from Nores:
“(A) Split Ortalis
araucuan (hírwacan) from O. guttata (characác). YES.
Vocal and plumage differences seem to me sufficient reason for splitting these taxa. Biogeographic
issues, however, are not evidence for considering them different species.
During the moister periods forest belts may have connected Amazonia and the
Atlantic forest. Ortalis guttata and
other Amazonian birds would have advanced toward the Atlantic forest and become
isolated again in the subsequent drier period. Consequently, there are at
present both species and subspecies in the Atlantic forest which are different
from those of Amazonia.
“(B) Split Ortalis squamata from O.
guttata. NO. As I
commented in Proposal #439, I consider that the Atlantic Region populations
belong to one species (O. araucuan)
with two subspecies (O. araucuan araucuan
and O. a. squamata).”
Comments
from Pacheco: “[YES to both] Influenciado diretamente pela opinião de Sick e
conhecendo os três táxons em campo, sinto-me confortável para admitir os táxons
em questão como independentes. Neste caso, o meu voto é coerente com aquele
exposto na proposta 439.”
Comments from Jaramillo:
“A –
YES. Separate araucuan from guttata. The biogeographic pattern,
differences in plumage and vocal data available convince me this is legitimate.
“B – YES. Although this
is less clear cut, for consistency (compared to other recognized Ortalis
species), this separation appears to be necessary. Because vocal and genetic
data have not been used to define species in this genus, at least consistent
use of differences in morphology as a way to separate species is appropriate.”
Comments from Cadena: “A.
YES, B. YES. The data available are not ideal, as no quantitative analysis of
vocal variation with appropriate geographic coverage and sample sizes has been
conducted. However, I agree with Mark in that vocal differences do appear
suggestive and in the context of how species are currently recognized in the
genus, these taxa likely merit species rank. Others have mentioned the need for
genetic data, but in cases like this, where taxa are all allopatric, I think
genetic data have actually little to offer. Some genetic differentiation in
neutral markers will undoubtedly exist, but such data would say very little
regarding the status of these populations as reproductively isolated entities,
which is what we are trying to judge here. So, based on how other species in
the group are defined, I am inclined to split them, although I am by no means
directly familiar with the taxa involved.”
Comments from Zimmer: “A) “YES, and (B)
“YES”. Splitting out both araucuan and squamata makes the most sense to me given the prevailing concept of
species limits within the rest of Ortalis. As Sick (1993) and Donegan (in the Proposal)
point out, the entire genus could be regarded as a superspecies. We are talking
about a large number of geographically isolated replacement species, which have
traditionally been recognized on the basis of morphological differences and
biogeography. Morphology within this
group appears to be evolutionarily conservative, with most species representing
minor variations on common themes. Given
all of this, it does strike me as odd that disjunct araucuan and squamata,
each occupying distinct biogeographic regions with high degrees of endemism,
and each morphologically distinct from other Ortalis, would continue to be treated as subspecies. This is especially true for araucuan, given that the range of
another Ortalis species (superciliaris) separates its range from
that of its presumed congener (guttata). I think that vocal differences between Ortalis species are more significant
than realized, but as with parrots, the distinctions are often difficult to
assess because in many (most?) recordings of these birds it is difficult to
impossible to know just how many birds are vocalizing at once (one, two, a
group, or even multiple groups). One
chachalaca of any given species will sound different from two, which will sound
different from several. In order to
compare apples to apples, you have to have adequate sample sizes of recordings
of a single individual, and even then, there may be sexual differences that
can’t be accounted for. So, it’s tough
to use vocalizations in this group, but I do think that once sound archives
have accumulated enough recordings of known numbers of individuals, we will see
vocal analyses that reveal significant differences between these various
populations.”
Comments from Remsen: “A) YES, and (B)
NO. Although I think the case is defensible
for araucuan (including squamata) as a separate species from O. guttata, the
same cannot be said for squamata as is evident in the proposal, and in agreement with
Manuel, I think it is best to treat it as a subspecies of O. araucuan
pending
more data.”
Comments from
Pérez-Emán: “A: YES. B: YES.
Morphological differences among these taxa seem to be small to elevate both
taxa to species. Also, vocal differences are difficult to evaluate (few
recordings and different vocalization scenarios as Kevin pointed out). However,
if current Ortalis taxonomy is based
on small plumage differences, then it makes sense to elevate these taxa to
species considering congruent (but small) morphological and vocal characters.
Biogeographically it also makes sense. I assume we will include subaffinis as a subspecies of guttata.”
Additional comments from T. Donegan:
“As set out in the proposal, the splitting of araucuan only (and not squamata) is
a reasonable approach. The SACC does not deal in subspecies. However, as set
out in the proposal, Part A, the better approach under a two-species approach
contra some comments above would involve splitting only araucuan but retaining squamata
with guttata. Whilst plumage
differences are pretty similarly differentiated among all three, the latter two
taxa are vocally most similar (as set out in the proposal and illustrated
briefly in sonograms in Donegan et al. 2010) whilst araucuan has most different note shapes in its songs, particularly
in the second note. I would be more inclined to take vocal cues as an
indication of species limits than seek to lump disjunct Atlantic populations on
biogeographic, plumage or other grounds. Lumping squamata with guttata but
splitting araucuan produces an
Atlantic plus Amazon guttata group
with two subspecies and without any other species' distribution bisecting their
ranges. This is a sensible outcome and guttata's
range would reflect a pattern found in many other species (see e.g. the outcome
of the recent Schiffornis turdina
proposal).
“Separately, we did carry out an analysis using
sonograms of the nature suggested by Kevin Zimmer in connection with the
aforementioned paper. Vocalisations with two birds calling can be analysed when
one looks carefully at sonograms and picks out the calls of different
individuals, which are typically at different frequencies: when two birds call
together this seems likely to be males and females which use different acoustic
frequencies. Where more than two birds call, it's certainly very difficult to
pick out what is happening, and one must scroll further through sonograms to
find instances where fewer birds vocalise in order to analyse song
structures."