Revise generic
boundaries in the Buteogallus group
Proposal (459) to South American
Classification Committee
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 Fábio 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 subdividivisiones . 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
Comments from Pacheco: “YES. A partir dos resultados do trabalho implicado nesta proposta – o qual pude acompanhar o desenrolar - e comentários adicionais de Fabio Raposo eu estou confortável (ainda que ciente da arbitrariedade envolvida) para aceitar este arranjo na forma como aqui exposto. Tenho para mim que o gênero Urubitinga de Lesson é feminino, logo a concordância correta deve ser, até evidência em contrário, U. coronata e U. solitaria.”
Comments from Jaramillo: “YES.
I think that this is a matter of taste to a great extent, and some of
the resistance to this proposal may be more subjective than logical (Urubitinga
with three species, it just doesn’t sit right although the data suggests that
the three are relatively closely related). The Solitary Eagle and Great
Black-Hawk do look alike, although in our minds we may overemphasize the
differences as that is what we have been focusing on in the field to tell these
birds apart! I think the authors have done a good and reasonable job of
separating out these hawks into genera that make sense.”
Comments from Remsen: “NO. After digesting all of the above, I think there are only three possibilities with any support: (1) the one in the proposal, (2) broad Buteogallus, and (3) as in proposal but retain Harpyhaliaetus. I have honestly vacillated among the three possibilities, and do not feel strongly about any of them. I really don’t think a broad Buteogallus is morphologically definable, but then again neither is even a narrowly defined Buteo (Proposal 460). Therefore, if even the narrowest delimitation of Buteo is as heterogeneous as broad Buteogallus, I don’t see why Buteo should survive as a taxon, whereas Buteogallus is dismembered 4-5 ways. Evolutionarily, the tendency of the buteonine lineage to show such plasticity and homoplasy contrasts strongly with, say, Accipiter or Circus. Taxonomically, however, it is unsettling.”