Proposal (450) to South American Classification Committee

Alter the traditional orders Pelecaniformes (excluding Phaethontidae) and Ciconiiformes to reflect new data on their relationships, and create a new order, Suliformes

NOTE: The following proposal was submitted to and passed NACC, and is here submitted with the authors’ permission.

Background: The AOU Check-list recognizes the Pelecaniformes and the Ciconiiformes as distinct orders. The Pelecaniformes (minus the Phaethontidae, see previous proposal), includes the following families:

Fregatidae (Frigatebirds)

Pelecanidae (Pelicans)

Phalacrocoracidae (Cormorants and Shags)

Anhingidae (Darters)

Sulidae (Gannets and Boobies)

and the Ciconiiformes consists of:

Ciconiidae (Storks)

Ardeidae (Herons and Egrets

Threskiornithidae (Ibises and Spoonbills)

Scopidae (Hamerkop—not in AOU area)

Balaenicipitidae (Shoebill—not in AOU area)

In the current check-list, these two orders are listed sequentially, reflecting their close relationship, as proposed in numerous studies (e.g., Sibley and Ahlquist 1990, Hedges and Sibley 1994, Van Tuinen et al. 2001, Ericson et al. 2006, Hackett et al. 2008). However, there is now substantial phylogenetic evidence for the paraphyly of these two groups, due to the Shoebill (Balaeniceps rex) being more closely related to the Pelecanidae than to the rest of the Ciconiiformes (Cracraft 1981, Livezey and Zusi 2001), or to the Pelecanidae being more closely related to the Shoebill and Hamerkop (Scopus umbretta) than to the rest of the Pelecaniformes (Van Tuinen et al. 2001, Ericson et al. 2006, Hackett et al. 2008).

The monophyly of the Pelecaniformes was questioned by Sibley and Ahlquist (1990) and again by Hedges and Sibley (1994) based on DNA-DNA hybridization work. The observed paraphyly of the Pelecaniformes with the Ciconiiformes led to placement of the Pelecaniformes, along with seven other closely related orders, in a greatly expanded Ciconiiformes (Sibley and Ahlquist 1990, Sibley and Monroe 1990, Hedges and Sibley 1994). However, we now know that this expanded Ciconiiformes is itself paraphyletic.

DNA sequence data suggest that neither the Pelecaniformes nor the Ciconiiformes is monophyletic, and generally support a close relationship between the Pelecanidae and the Shoebill (Van Tuinen et al. 2001, Ericson et al. 2006, Hackett et al. 2008). Further, it appears that the Ciconiidae is not sister to the other families traditionally placed in the Ciconiiformes, but is instead sister to the remaining “Ciconiiformes”+Pelecaniformes (Hackett et al. 2008) or its relationship is unresolved (Ericson et al. 2006).

Given that the Pelecaniformes and Ciconiiformes are paraphyletic, there are three main alternatives to be considered. These would result in one, four, and three orders, respectively. The first would lump the Pelecaniformes (excluding the Phaethontidae) with the Ciconiiformes to create an expanded Ciconiiformes. The second would split the Pelecaniformes (again excluding the Phaethontidae) and Ciconiiformes into two orders apiece. Following the Hackett et al. (2008) phylogeny, the Pelecaniformes would be split into the Suliformes (Anhingidae, Phalacrocoracidae, Sulidae, Fregatidae) and the Pelecaniformes (Pelecanidae; Balaenicipitidae and Scopidae from outside our area), and the Ciconiiformes into the Ciconiiformes (Ciconiidae) and the Ardeiformes (Ardeidae, Threskiornithidae). The third option would split the Suliformes (as above) from the Pelecaniformes and the Ciconiidae from the rest of the erstwhile Ciconiiformes (as above), but would lump the Ardeiformes (as above) and the Pelecaniformes (as above), creating a revised Pelecaniformes (Ardeidae, Threskiornithidae, Pelecanidae; Balaenicipitidae and Scopidae from outside our area).

The genetic data provide the strongest support for the third option (three orders). In Hackett et al. (2008), the bootstrap value for a completely lumped Ciconiiformes (option 1) is 81%; this node is not present in the tree of Ericson et al. (2006), which means it received less than 0.95 posterior probability. The bootstrap value for a monophyletic Ardeiformes consisting of the Ardeidae and the Threskiornithidae (as in option 2) was 72% and the posterior probability for this node was again less than 0.95 (i.e., it was not present in the tree). In contrast, the three order-defining nodes in option 3 all receive 88-100% bootstrap support and more than 0.95 posterior probability. If we are reorganizing these orders based on genetic data, we would suggest option three as the best choice.

Recommendation: We recommend altering the makeup of the Pelecaniformes and Ciconiiformes and creating the new order Suliformes, as specified in option 3 above. The order of taxa in the AOU area would be as follows, based on the phylogeny of Hackett et al. (2008).

Ciconiiformes

Ciconiidae (Storks)

Suliformes

Fregatidae (Frigatebirds)

Sulidae (Gannets and Boobies)

Phalacrocoracidae (Cormorants and Shags)

Anhingidae (Darters)

Pelecaniformes

Pelecanidae (Pelicans)

Ardeidae (Herons and Egrets)

Threskiornithidae (Ibises and Spoonbills)

Literature Cited:

Cracraft, J. 1981. Toward a phylogenetic classification of the recent birds of the world (class Aves). The Auk. 98(4) 681-714.

Ericson, P.G.P., Anderson, C.L., Britton, T., Elzanowski, A., Johansson, U.S., Källersjö, M., Ohlson, J.I., Parsons, T.J., Zuccon, D., and Mayr, G. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biol. Lett. 2 543-547.

Hackett, S.J, Kimball, R.T., Reddy, S., Bowie, R.C.K., Braun, E.L., Braun, M.J., Chojnowski, J.L., Cox, W.A., Han, K., Harshman, J., Huddleston, C.J., Marks, B.D., Miglia, K.J., Moore, W.S., Sheldon, F.H., Steadman, D.W., Witt, C.C., and Yuri, T. 2008. A phylogenomic study of birds reveals their evolutionary history. Science. 320 1760.

Hedges, S.B. and Sibley, C.G. 1994. Molecules vs. morphology in avian evolution: The case of the “pelecaniform” birds. Proc. Natl. Acad. Sci. USA. 91 9861-9865.

Kennedy, M. and Spencer, H.G. 2004. Phylogenies of the frigatebirds (Fregatidae) and tropicbirds (Phaethontidae), two divergent groups of the traditional order Pelecaniformes, inferred from mitochondrial DNA sequences. Molecular Phylogenetics and Evolution. 31 31-38.

Livezey, B.C. and Zusi, R.L. 2001. Higher-order phylogenetics of modern Aves based on comparative anatomy. Netherlands Journal of Zoology. 51(2) 179-205.

Sibley, C.G. and Ahlquist, J.E. 1990. Phylogeny and classification of birds. Yale. Univ. Press, New Haven, Connecticut.

Sibley, C.G. and Monroe, B.L. 1990.

Van Tuinen, M., Butvill, D.B., Kirsch, J.A.W., Hedges S.B. 2001. Convergence and divergence in the evolution of aquatic birds. Proc. R. Soc. Lond. B. 268 1345-1350.

Shawn Billerman, Irby Lovette, Terry Chesser, August 2010

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Comments from Zimmer: “YES. This seems to be the solution (Option #3) that best fits the genetic data, and makes the most intuitive sense to me relative to the placement of Scopidae and Balaenicipitidae.”

Comments from Stiles: “YES – Suliformes clearly makes good sense; although putting herons and ibis in Pelecaniformes was at first jarring to my sense of what a order “should” be, I note that in the next proposal the Gruiformes, even after paring off several unrelated families, still contains such totally different-looking birds as bustards and sungrebes, makes me resigned to (if not wholly comfortable with) a comparably heterogeneous Pelecaniformes. Oh well – Cochlearius could be mistaken for a shoebill on a dark night.”

Comments from Pacheco: “YES. O novo arranjo proposto deriva de um conjunto recente de estudos e acomoda de forma mais coerente a interrelação entre as diferentes famílias antes subordinadas aos Pelecaniformes.”

Comments from Nores: “YES. The separation in three orders is a good option, which is in accord with the two main molecular analyses (Ericson et al. 2006, Hackett et al. 2008). However, one question that arises is: why Suliformes and not Phalacrocoraciiformes? Both genera (Sula and Phalacrocorax) were created by Brisson in 1760, and the first species of each taxon (Pelecanus bassanus=Sula bassanus and Pelecanus carbo= Phalacrocorax carbo) was described in 1758 by Linnaeus. Both species were published in Syst. Nat. Ed. 10, p.133. In the case of a total draw, I would take into account the importance of each group (39 vs. 9 species) and I would put Phalacrocoraciiformes.”

Comments from Jaramillo: “YES. Option three is the best. Can someone confirm Manuel’s assertion? Is Suliformes being used in error, or does it have precedence somehow?”

Additional comments from Remsen: “Names of higher-level taxa do not follow the same rules of priority as do genera and species; the name with priority is the oldest in the literature, and if the order has not been named previously, then the name can be chosen by those who first name the order. Edward Dickinson kindly sent me the following quote as well:

"If Sula and Phalacrocorax are included in the same family-level taxon (e.g. superfamily), then Sulidae Reichenbach, 1849 (1836) (Sula Brisson, 1760) has priority in preference to Phalacrocoracidae Reichenbach, 1849-50 (1836) (Phalacrocorax Brisson, 1760), because the name Suloidea has been consistently used in avian classification as a superfamily name." [Bock, W. J. (1994). History and nomenclature of avian family-group names. Bulletin of the American Museum of Natural History, 222: 1-281.]