Proposal (460) to South American Classification Committee
Revise generic boundaries in the Buteo group
Effect on South American CL:
This would revise generic boundaries extensively in Buteo and Leucopternis.
Background
& New Information: For several years, we’ve had plenty of
indication that the current boundaries of the genera Buteo, Leucopternis, and
relatives 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:
12a.
Genetic data (Raposo et al. 2006, Lerner et al. 2008, Raposo do Amaral et al.
2009) indicate that the genus Leucopternis is polyphyletic; as currently
defined, Leucopternis includes at least three distinct groups that are
not each others' closest relatives: (1) L. melanops, L. kuhli,
and L. semiplumbeus; (2) L. albicollis, L. occidentalis,
and L. polionotus; (3) L. plumbeus, L. schistaceus,
L. lacernulatus, which are intermingled within a group with Buteogallus and
Harpyhaliaetus; and (4) L.
princeps, whose placement is uncertain.
Raposo do Amaral et al. (2009) recommended placing princeps in a monotypic genus Morphnarchus, plumbeus in a new monotypic genus Cryptoleucopteryx, schistaceus
in Buteogallus, and lacernulatus in a new monotypic genus Amadonastur. SACC proposals needed.
18.
Genetic data (Riesing et al. 2003) indicate that Geranoaetus is the
sister taxon to Buteo polyosoma/B. poecilochrous
and that maintenance of a monotypic genus is not warranted; it had been placed
in Buteo formerly (e.g., Wetmore 1933, Hellmayr & Conover 1949,
Friedmann 1950), but recent authors have generally followed Amadon (1963), who
suggested that it might be closer to Buteogallus or Leucopternis
than to Buteo. Clark (2006) disputed Amadon's rationale for maintaining
it is a genus separate from Buteo. SACC proposal to merge Geranoaetus
into Buteo did not pass. New genetic data (Lerner et al. 2008) provide even
stronger evidence for merger of Geranoaetus, at least as currently
defined, because it is the sister species to B. polyosoma. SACC proposal to merge Geranoaetus
into Buteo did not pass.
Raposo do Amaral et al. (2009) further confirmed that Geranoaetus is the sister to Buteo polyosoma
sensu lato. SACC
Proposal needed.
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 (sorry for
the poor resolution of the screen grab):
The
Buteo group itself (Group G) is
strongly supported as a monophyletic group as is sister relationship to the Buteogallus group (Group H). It includes everything in our current
classification in Buteo plus Parabuteo, Geranoaetus, and most Leucopternis
(minus the 4 species that are part of Group H; see Proposal 459).
Analysis
and Recommendation:
Virtually every critical node in Group G’s tree has strong support. Our current Buteo and Leucopternis
are both polyphyletic, and so changes must be made. So, 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. However, one option would
be to expand Buteo to include all
species in Group G. Even the two
outliers, “Leucopternis” princeps (placed by Raposo do Amaral et
al. in a resurrected monotypic genus Morphnarchus)
and Buteo magnirostris (placed by Raposo do Amaral et al. in a resurrected
monotypic genus Rupornis), don’t
really stand out (to me anyway) as beyond the range of variation encompassed
even with a narrow Buteo). In my subjective view, there is so much
variation among the species in narrowly defined Buteo in terms of color, shape, behavior, and size that adding the
other 6 genera recognized by Raposo do Amaral et al. does not really add to its
phenotypic heterogeneity. Narrow Buteo includes heavy, robust species of
open country such as B. regalis and
small chunky species of forest such as B.
platypterus. It includes B. nitidus, long placed in a monotypic
genus Asturina. It includes blackish species such as B. albonotatus,
gray-plumaged species such as B. nitidus,
and relatively pale species (ventrally) such as B. brachyurus. It also
includes all Old World Buteo sampled
so far. More importantly, Raposo do
Amaral’s et al.’s Buteo is not
unequivocally monophyletic if nitidus
is included, and in fact one could make a case for resurrection of Asturina based on weak support for the
node that links it to core Buteo.
A
YES vote on this proposal would be for adopting Raposo do Amaral et al. as is,
namely recognize 7 genera (in the following sequence) for the group instead of
4, as follows:
Morphnarchus (monotypic; formerly L. princeps)
Rupornis (monotypic; formerly B. magnirostris)
Parabuteo (unicinctus
plus leucorrhous)
Geranoaetus (to also include B. polyosoma and B. albicaudatus,
a combination we’ve voted down previously)
Pseudastur (resurrected for L. albicollis/occidentalis;
this might actually become monotypic given that albicollis is evidently paraphyletic with respect to occidentalis in their tree)
Leucopternis (melanops,
kuhli, semiplumbeus)
Buteo (nitidus,
platypterus, albigula, brachyurus, swainsoni, galapagoensis, albonotatus,
ventralis)
A
NO vote would be to broaden generic boundaries, from small tweaks to as much as
including everything in Buteo. If this proposal fails, I’ll write additional
proposals to take into account broader generic limits. I do not have a strong recommendation, but I
am going to vote NO, given the points made about on the heterogeneity of narrow
Buteo. Because delimiting genera is a subjective
exercise as long as each is monophyletic, I hope to hear others opinions, and
my NO vote is not a firm one.
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 Bret Whitney:
“I like Rupornis for Roadside Hawk. It’s a bizarre bird, frankly, a highly
successful New World raptor not quite like anything else, intermediate
morphologically and behaviorally between Accipiter
and small Buteo with distinctive
vocalization patterns and behaviors (nothing else is even close to as
consistently vocal as Rupornis, for
instance). To lump it into Buteo just obscures the picture, in my
opinion. Yeah, I know, having such
different types as Ferrug and Broad-winged in one genus is also “uncomfortable”
-- but I guess the best path forward is to split out only what seems clearly
divergent when ornithologists can agree that there’s good concordance among
various datasets.”
Comments from Robbins:
“NO, to be consistent with my comments under proposal 459. I would also add vocalizations to Van’s
comments about variation in Buteo; it
is considerable among even closely allied species.”
Comments solicited from Fabio Raposo:
“Thanks very much to Van and the committee for
requesting comments and letting us be part of this discussion. A few important points on this one (for more
general comments on the buteonine proposals, please see SACC #459):
Yes, there is a lot of heterogeneity in Buteo,
even when narrowly defined as we did.
However, the other monophyletic groups treated in our paper as
genera are far from heterogeneous, since they have clear identities as groups
(see below, we explicitly indicate why we strongly support that point of
view). Exactly for this reason, we don’t understand why an enormous,
uninformative and undiagnosable Buteo would be a better option - why add
more heterogeneity to Buteo, when we can indicate specific characteristics of
each of those clades? Furthermore, our classification is
"testable" - those with access to a good bird collection will clearly
see those groups/characters in 10 minutes with the birds on a table (this is
something that we did over and over again before closing this paper), while a
catchall Buteo has no concrete identity as a group. A huge,
undiagnosable, species-hungry Buteo (by the way, rejected by the
committee twice when dealing with Geranoaetus - see SACC #282 and SACC
#387) would be unnecessarily in the top 10 largest avian genera ever.
--
genus Leucopternis (L. semiplumbeus, L. kuhli and L. melanops):
generally speaking, small, black and white Neotropical buteonine hawks,
found exclusively in forests. Plain white underparts, narrow black streaks
or solid gray on the sides of the neck; short wings (primaries extending to
less than half of tail); plain black tails with one medial white band in adults
(and two white bands in young birds).
--
genus
Pseudastur (P. albicollis, P. occidentalis and P. polionotus):
generally speaking, large, black and white Neotropical buteonine hawks
- found exclusively in forests. White underparts, plain white tails with a
single black band, and secondaries and tertials with conspicuous white tips.
--
genus Geranoaetus (G. melanoleucus, G. polyosoma and G.
albicaudatus): generally speaking, large, dark headed open
vegetation buteonine hawks - mostly Neotropical. Densely feathered faces,
solid black or gray sides of the neck, white underparts with flanks (and sometimes
belly) finely streaked, long primaries that reach the tip of the tail; densely
barred tails with narrow blackish bars and a subterminal large black band, or
entirely solid black.
--
genus Parabuteo (P. unicinctus and P. leucorrhous): Plumage
is strikingly similar between those two species - overall black or dark
brown coloration, white rump and undertail coverts, and mostly rufous or light
brown thighs.
On
the other hand, Rupornis magnirostris (as well indicated by Bret)
and Morphnarchus princeps are very divergent species,
isolated from the rest of the tree by lots of evolutionary time and
autapomorphic characteristics - and that’s why monotypic genera fit best for
those two. Finally, a correction to
the proposal: Pseudastur also includes L. polionotus, which is
clearly a good species, sister to the Amazonian subspecies of L. albicollis.
So even if the trans-Andean L. albicollis subspecies are lumped
with L. occidentalis, there still would be three species (L.
polionotus, L. albicollis from Amazonia, and trans-Andean L.
albicollis+L. occidentalis) - so nothing to worry about this genus
becoming monotypic.