Proposal (383) to South American Classification Committee

Separate Accipitriformes from Falconiformes

Effect on SACC: This would split our current order Falconiformes into two, with only the Falconidae remaining in the Falconiformes.

Background: Most classifications, including ours, recognize a broadly defined Falconiformes to include not only the Falconidae but also all the hawks, eagles, kites, and relatives plus Pandionidae and Sagittariidae. Without doing a thorough literature review, I think I can get away with saying that there has always been some doubt about the monophyly of broad Falconiformes. Google gives something like 49,00 hits on Accipitriformes, including an official Wikipedia entry, and Google Scholar produces 492 citations that use Accipitriformes. Other than the obvious superficial similarities, I am not aware of any solid genetic data that supports the monophyly of our current Falconiformes. Livezey & Zusi (2007) consider the Strigiformes as sister to broadly defined Falconiformes, with Pandion sister to Falco +Polyborus. However, this same morphological analysis still supports a sister relationship between Gaviiformes and Podicipediformes, which is not consistent with any genetic dataset. Therefore, many conclude that even sophisticated morphological analyses cannot distinguish convergence from true relationships.

New data: Hackett et al.’s (2008) massive analysis set new standards in gene sampling: 32 kilobases of aligned DNA sequences that included 19 nuclear loci. They found strong support (98% Maximum Likelihood bootstrap) for a node (“F”) that includes Falconiformes broadly defined plus Strigiformes …. But that clade also includes Passeriformes, Psittaciformes, Cariamiformes, Piciformes, Coraciiformes, Trogoniformes, and Coliiformes … and thus only marks one of the major groups of modern birds. The nodes within this clade are not as strongly supported, but Node B, with 73% bootstrap support shows Falconidae as sister to Psittaciformes + Passeriformes. [Tangentially, I am impressed with the similarities between falcons and parrots that include the bony tubercle in the nares, the notched mandible, and nesting biology – yes, I recognize that tallies of similarities do not count per se]. The branching pattern among the remaining groups is probably best considered a polytomy, except for Node D, which shows Leptosomus of Madagascar as sister to Coraciiformes + Piciformes + Trogoniformes. Sagittariidae + (Pandionidae + Accipitridae) is supported as a monophyletic group with 100% support.

Analysis and Recommendation: Given the absence of any non-morphological data that I know of that supports the monophyly of broadly defined Falconiformes, given that the best and most thorough analysis to date does not support this monophyly, and given the long history of doubts concerning this monophyly reflected in widespread use of Accipitriformes, I conclude that he burden-of-proof now lies on those who would consider our Falconiformes as monophyletic … and so I recommend a YES on this. However, as pointed out to me by Mike Braun, statistically one cannot reject the possibility that the traditional Falconiformes is monophyletic – to quote from an active MS by Dave Steadman et al. “while none of the analyses in Hackett et al. (2008) supported monophyly of the traditional Falconiformes, these same analyses were not able to reject monophyly of this group.” So, a NO vote would indicate that the possibility of monophyly has to be rejected, and a YES vote would indicate that support for them as a monophyletic group is uncorroborated and that nonmonophyly is strongly suggested by the data.

Lit Cit

HACKETT, S. J., R. T. KIMBALL, S. REDDY, R. C. K. BOWIE, E. L. BRAUN, M. J. BRAUN, J. L. CHOJNOWSKI, W. A. COX, K.-L. HAN, J. HARSHMAN, C. J. HUDDLESTON, B. D. MARKS, K. J. MIGLIA, W. S. MOORE, F. H. SHELDON, D. W. STEADMAN, C. C. WITT, AND T. YURI. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320: 1763-1768.

LIVEZEY, B. C., AND R. L. ZUSI. 2007. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zoological J. Linnean Society 149: 1-95.

Van Remsen, November 2008

Comments from Stiles: “YES. The massive data from the Hackett et al. study in particular make it clear that the traditional Falconiformes is polyphyletic, with the adaptations for diurnal raptorial habits being convergences between the falcons et al. and the acciptrids et al.; hence separate orders are clearly justified.”

Comments from Nores: “YES. Del análisis molecular de Hackett et al. (2008) surge claramente que Accipitridae y Falconidae son dos grupos muy diferentes, a pesar del garan parecido morfológico que presentan las especies. Este es para mi uno de los ejemplos más notables de convergencia que muestra que el análisis sólo morfológico, como se ha acostrumbrado hacer, no siempre es el correcto. Lo que si, ese mismo análisis muestra que Cathartidae está muy cerca de Accipitridae y no debería ser considerado un orden aparte. Por esta razón, pongo ahora un NO a la propuesta No. 361, que todavía no había contestado.”

Additional comments from Remsen: “With respect to Manuel’s point concerning Cathartiformes, the Hackett et al. data do not confirm a monophyletic Accipitriformes if Cathartidae is included. Close, yes, but not necessarily forming a monophyletic group. Further, I support Order rank for cathartids regardless of possible sister status with accipitrids because this lineage is as old or older than most lineages ranked as orders.”

Comments from Jaramillo: “YES – This is indeed an amazing example of convergence, and I accept that it makes sense to separate Accipitriformes from Falconiformes. I have also been impressed with similarities between parrots and falcons, once I thought about them upon reading this paper. There is a lot there to “chew on” that makes sense.”

Comments from Zimmer: “YES. I also agree with Van regarding Order rank for cathartids.”

Comments from Pacheco: "YES. Plenamente justificável a partir dos dados genéticos.”