Proposal (459) to South American Classification Committee
Revise generic boundaries in the Buteogallus
group
Effect on South American CL:
This would revise generic boundaries extensively in Buteogallus, Leucopternis,
and related genera.
Background
& New Information: For several years, we’ve had plenty of
indication that the current boundaries of genera in the vicinity of Buteogallus in our current
classification are a mess. Raposo do
Amaral et al. (2009) have produced a comprehensive phylogeny of buteonine
hawks, and their data will form the primary basis for this proposal. Findings from earlier papers (see Notes
below) are largely consistent with Raposo do Amaral et al. (2009) and will not
be discussed further. Two of the
relevant Notes from our SACC classification are:
14b.
Buteogallus urubitinga was formerly treated in
the monotypic genera Urubitinga (e.g.,
Hellmayr & Conover 1949) or Hypomorphnus (Pinto 1938,
Friedmann 1950, Phelps & Phelps 1958a), but see
Amadon (1949) and Amadon & Eckelberry (1955) for rationale for placement in
Buteogallus. Genetic data (Lerner & Mindell 2005), however, indicate
that Buteogallus urubitinga and B. anthracinus are not
sisters and that the former is more closely related to Harpyhaliaetus
(see also Amadon 1949, Raposo et al. 2006). Raposo do Amaral et al. (2009)
recommended that they be treated in the genus Urubitinga. Proposal badly needed.
15.
Buteogallus meridionalis was formerly (e.g., Pinto 1938, Hellmayr & Conover 1949, Friedmann 1950, Phelps
& Phelps 1958a, Meyer de Schauensee 1970) placed in the monotypic genus Heterospizias,
but most recent classifications follow Stresemann & Amadon (1979) and
Amadon (1982) in merging this into Buteogallus. <incorp. Griffiths
(1994)>
Recent genetic data (Raposo et al. 2006, 2009, Lerner
et al. 2008) indicate that Buteogallus
is paraphyletic with respect to Harpyhaliaetus and certain Leucopternis.
Proposal needed. Buteogallus meridionalis
was formerly (e.g., Peters 1931, Friedmann 1950) placed in the subfamily
Accipitrinae, but Plótnik (1956a) showed that morphological data favored
placement in the Buteoninae, as confirmed by genetic data (Lerner et al. 2008,
Raposo do Amaral et al. 2009).
Raposo
do Amaral et al.’s (2009) taxon sampling (105 specimens, 54 species) and gene
sampling (6000 bp of 9 genes, mitochondrial and nuclear) is exemplary. I doubt that anyone will produce a better
data set anytime soon. This proposal
deals only with their Group H, whose monophyly has excellent support; the
relevant portion of their tree (from their Fig. 3) is pasted in here:
Therefore,
the problems in current classification are even worse than revealed in earlier
papers, with most species requiring a change in genus. Raposo do Amaral et al. had to name two new
genera to avoid combining all species into one large, heterogeneous Buteogallus. The latter solution is actually an
alternative to be explored if this proposal does not pass. Group H includes all the taxa previously
associated with Buteogallus, within
which generic limits have been historically fluid, and adds in three species
from Leucopternis, two of which are
dark like most of the Buteogallus
group but also one (lacernulatus)
that has more typical black-and-white Leucopternis
plumage. What a mess. At least one of the former Leucopternis, schistaceus, has a riverine habitat like its new sister taxa, Buteogallus sensu stricto.
Analysis
and Recommendation:
Virtually every critical node in Group H’s tree has strong support. Therefore, the only point of real discussion
is the subjective exercise of how broadly to delimit the genera. Raposo do Amaral et al. have defined these
very narrowly, and as stated above, one option would to be expand Buteogallus to include all nine species
in Group H. Even the outlier, plumbeus, placed in a newly described
genus Cryptoleucopteryx, has no
single character that diagnoses it, but only a unique combination of
characters. I do not know enough about
voice and behavior of these birds to say anything about whether such a broad
genus would violate subjective notions of homogeneity in currently
circumscribed hawk genera, but my first instinct is that it wouldn’t be any
more heterogeneous than even a narrowly defined Buteo.
If
we adopt as is the Raposo do Amaral et al. classification, the linear sequence
would look like this:
Cryptoleucopteryx plumbea (the new genus is feminine)
Buteogallus anthracinus (includes “subtilis”)
Buteogallus aequinoctialis
Buteogallus schistaceus
Heterospizias meridionalis
Amadonastur lacernulatus
Urubitinga urubitinga
Urubitinga solitarius
Urubitinga coronatus
I
do not know the former Harpyhaliaetus
species well, but I have reservations about placing Great Black Hawk and
Solitary Eagle in same genus if they are to be narrowly defined – why not just
retain Harpyhaliaetus? Using just genetic distance suggests that it
as roughly as distinct from Urubitinga
urubitinga as are the other genera in the proposed classification.
A
YES vote would be to adopt this classification as is. A NO vote would be to broaden generic
boundaries, from as little as reinstating Harpyhaliaetus
to as much as including everything in Buteogallus. If this proposal fails, I’ll write additional
proposals to take into account broader generic limits. I do not have a recommendation. Because delimiting genera is a subjective
exercise as long as each is monophyletic, I wait to hear from those with more
experience with these birds. Please help
solicit such opinions.
Literature Cited:
RAPOSO DO AMARAL, F.,
F. H. SHELDON, A. GAMAUF, E. HARING, M. RIESING, L. F. SILVEIRA, AND A.
WAJNTAL. 2009. Patterns and processes of diversification in
a widespread and ecologically diverse avian group, the buteonine hawks (Aves,
Accipitridae). Molecular Phylogenetics and Evolution 53: 703-715.
Van
Remsen, August 2010
=========================================================
Comments from Stotz:
“NO Somehow the creation of 2 new genera
and the use of 5 genera for a total of 9 species seems like too much. My preference would be for 1 genus or
possibly 2 (Buteogallus and Cryptoleucopteryx) for this group. There are other treatments that are possible
up to 6 genera, but I think, given that the taxa we currently treat in Buteogallus are scattered from one end
of the tree to the other, that just inserting all of those taxa into Buteogallus is the way to go. I am a little alarmed by Leucopternis lacernulatus being in the middle of this, but
otherwise this basically fits pretty well with my intuition.”
Comments from Bret Whitney:
“In full agreement
with Remsen that “delimiting genera is a subjective exercise as long as each is
monophyletic”, the problem remains one of defining the boundaries of
“monophyly”. With little more to “guide” me beyond a feeling of comfort
within indefinable (for me) limits of similarity among species within the context
of natural histories and biogeographic speciation patterns... I’d be most
content with recognizing the (previously unsuspected, for me) close
relationship of Buteogallus meridionalis and Leucopternis
lacernulatus with placement together in Heterospizias; and
recognition of the somewhat deeper (as I understand it?) split between the
close pair of Harpyhaliaetus solitarius + H. coronatus and Buteogallus
urubitinga by maintaining these two groups in separate genera: Harpyhaliaetus
and Urubitinga.”
Comments from Robbins:
“NO. Instead of creating multiple genera
(as Van points out this is similar to the broadly defined Buteo; voice, plumage,
& behavior is extremely broad in that genus even within a single
subcontinent), I would prefer including everything in Buteogallus.”
Comments solicited from Fabio Raposo:
“Thanks
very much to Van and the committee for requesting comments and letting us be
part of this discussion. Van did a great job translating our trees in this
series of proposals. I agree that this is a really messy (and difficult) group,
and it took a lot of time and discussion to end up with the classification that
we proposed. A few important points:
- As
commented by Bret and Stotz, clustering of L. lacernulatus and B.
meridionalis was unexpected to us, too. L. lacernulatus is a black
and white forest species endemic to the Atlantic Forest of Brazil, while Buteogallus
meridionalis is a mostly brown/rufous, open-vegetation widespread species
of SA savannahs. This relationship is, however, very well supported. In
addition, all species in clade H are represented by at least one
vouchered muscle sample (including perhaps the only vouchered fresh muscle
samples of L. lacernulatus and H. coronatus in the world – skins
available at MZUSP). Furthermore, close relationship of L.
lacernulatus and B. meridionalis to species in clade H echoes two
previous papers, one of them performed by independent researchers (Amaral et
al. 2006; Lerner et al. 2008). Evolution acts in unpredictable ways, and one
possibility is that those two species represent relicts of once larger clades
affected by extinction, for example. We do not support their lumping in a
single genus exactly because of their high divergence in plumage, ecology
and evolutionary time, and for this reason we proposed the resurrection of Heterospizias
for B. meridionalis and the new generic name Amadonastur for L.
lacernulatus.
-
Contrary to the L. lacernulatus/B. meridionalis case, very close
resemblance of H. solitarius and B. urubitinga plumages (in some
aspects much closer than between H. solitarius and its sister H.
coronatus) has lead us to conclude that they would be better represented by
one genus. Please also compare, using figure 4 (see below why), divergence
between L. lacernulatus and B. meridionalis and divergence among
the three species that we propose to be in Urubitinga.
- Branch
lengths of Figures 1 and 3 should be interpreted with caution, since they may
have no meaning if one wants to consider divergence as a measure of time: the
data do not evolve in a clock-like manner. In other words, long branches may
not reflect long evolutionary time, and short branches do not necessarily
reflect short evolutionary time. If time may contribute to this
discussion, figure 4 would be more suitable (a relaxed-clock
analysis, that incorporates the variation in rates of molecular
evolution responsible for the violation of a strict molecular clock, and
includes very conservative confidence intervals). Interestingly, despite the large
confidence intervals, the genera as we proposed would split from the rest of
the tree approximately close in time (see nodes 47, 48, 50, 55, 57, 59 and 70).
- In any
case, many nomenclatural changes are necessary, and different schemes would
have similar effects (e.g. our proposal or any made so far would need from five
to six changes for clade H).
- Finally, if the idea is to
indicate phylogenetic relationships, broadly defined genera and monotypic
genera in practice are equally little informative. However, if using a few
monotypic genera (which are justifiable in cases
of divergent, autapomorphic species) makes it possible to
indicate so many morphologically homogeneous groups (as we believe to be the
case with Buteogallus and Urubitinga here - but
also see SACC 460), perhaps it makes less harm to have a few monotypic
genera than considering a lot of differences in large, undiagnosable and very
heterogeneous groups (as it would be in including clade H in Buteogallus, or
even worse, clade G in an extremely inclusive Buteo cited in proposal
460). But if we are to recognize larger
groups, it is crucial to define them in terms of diagnostic characters and/or
the most objective criteria as possible – i. e. it is always possible to indicate (based
on published data, of course, in terms of plumage patterns, ecology, vocal
characters, behavior, or any other criteria) why to attach a name to a group of
species. Only then we would have comparable competing schemes, supported by
concrete evidence.
Amaral, F. R., Miller, M.J., Silveira, L.F.,
Bermingham, E., Wajntal, A. 2006. Polyphyly of the hawk genera Leucopternis and Buteogallus (Aves, Accipitridae): multiple habitat shifts during
the Neotropical buteonine diversification. BMC Evolutionary Biology 6, 1
Lerner, H.R.L., Klaver, M.C., Mindell, D.P.,
2008. Molecular phylogenetics of the buteonine birds of prey (Aves,
Accipitridae). Auk 125, 304–315.
Comments from Zimmer:
“NO. I’m okay with some of the proposed
Raposo do Amaral et al. classification, but not all of it. And I really don’t like the idea of throwing
all of these birds into a heterogeneous Buteogallus. I think there are good reasons why L. plumbea shows up as an outlier in
this classification. It is vocally very
distinctive from everything else, including regular indulgence in some pretty
wild male-female duets, in which the respective vocalizations of the male and
female appear to be sexually stereotypical.
It also seems pretty different ecologically from the others, in being a
forest-interior bird that doesn’t regularly soar. I’d really be inclined to put it in its own
genus, as Raposo do Amaral et al. have done.
I’d also separate out the two Harpyhaliaetus
– they form a distinctive pair, and I don’t see any real advantage in placing
them in Urubitinga. Removing urubitinga
from Buteogallus, and moving schistaceus into there makes perfect
sense given the existing data. I’d be
inclined to follow Raposo do Amaral et al. in keeping meridionalis and lacernulatus
in separate genera even though they are apparently sister taxa. Aside from plumage differences, there are
some pretty obvious structural, ecological and behavioral differences. Putting those two in the same genus would
make delineating other genera on the grounds of avoiding too much heterogeneity
hard to defend.”
Comments from Stiles: “YES.
After mulling over the proposed changes, I find myself in pretty complete
agreement with Fabio on this one. First,
having had the opportunity to observe the Solitary Eagle frequently in Costa
Rica, I was impressed with its vocal, morphological and behavioral similarity
to (B.) urubitinga and I fully support congeneric status for these two,
with (H.) coronatus along for the ride. Although I don’t know lacernulatus, everything I’ve read about
it makes me averse to including it in a genus with the totally different meridionalis, hence monotypic genera for
both seem best. I also don’t know plumbea but Kevin’s comments make
separate (monotypic) status for it palatable as well. “
Comments from Nores: “NO, pero que es casi un
YES. Aunque el análisis de Raposo et al. me parece
excelente, no soy de la idea de hacer tantas subdivisiones . A pesar de las
diferencias que existen morfológicas y ecológicas entre Buteogallus meridionalis y Leucopternis
lacernulatus, yo los pondría juntos en el género Heterospizias ya que genéticamente están muy emparentados. Por
lo tanto la secuencia sería la siguiente:
Cryptoleucopteryx
plumbea
Buteogallus schistaceus
Buteogallus anthracinus (includes “subtilis”)
Buteogallus aequinoctialis
Heterospizias meridionalis
Heterospizias lacernulatus
Urubitinga urubitinga
Urubitinga solitarius
Urubitinga coronatus