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”)
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.
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:
Buteogallus anthracinus (includes “subtilis”)