Proposal (290) to South American Classification Committee
Recognize Cariamidae in their own Order, Cariamiformes
Effect on SACC: This would remove the Cariamidae from the Gruiformes and create a separate order for them, the Cariamiformes.
Background and New information: That the current Gruiformes is a polyphyletic grouping has been suspected for most of this century. See Sibley & Ahlquist (1990) for a review. Here's what we say with respect to inclusion of the Cariamidae at the Note under Gruiformes:
"The extreme morphological heterogeneity among the families of the Gruiformes has always made the monophyly of this order suspicious (see Cracraft 1981, Sibley & Ahlquist 1990). Although Sibley & Ahlquist's DNA-DNA hybridization data provided support for a monophyletic Gruiformes, subsequent genetic data have failed to do so. Although Fain & Houde's (2004), Ericson et al.'s (2006), and Fain et al.'s (2007) genetic data strongly support the monophyly of a core group of gruiform families that consists of the Gruidae, Aramidae, Psophiidae, Rallidae, and Heliornithidae, support for inclusion of other traditional gruiform families is weak or nonexistent. Concerning families found in South America, Fain & Houde (2004) and Ericson et al. (2006) found that the Eurypygidae does not belong in the Gruiformes but rather in a major, separate radiation of the Neoaves, with the Rhynochetidae the likely sister family of the Eurypygidae (see also Houde et al. 1997, Livezey 1998, Cracraft et al. 2004), and that the Cariamidae (and also the Old World Otididae) is in an altogether different branch of the Neoaves than are the true Gruiformes (see also Livezey & Zusi 2001, Mayr & Clarke 2003, Ericson et al. 2006). Proposal needed to remove these from Gruiformes <wait for at least one more dataset from TOL/Early Bird projects?> . Recent morphological data (Livezey & Zusi 2007) support the monophyly of the traditional Gruiformes except that the Rallidae (represented only by Porphyrula) and Heliornithidae (and Old World Turnicidae and Mesitornithidae) might belong in the Charadriiformes."
The studies that have supported placement of the Cariamidae in the Gruiformes were Cracraft's (1982) analysis of osteological characters, Sibley & Ahlquist's (1990) DNA-DNA hybridization study, and Livezey & Zusi's (2007) analysis of morphological characters.
However, four independent data sets now show that the Seriemas are not members of the core gruiforms. Mayr & Clarke (2003), using morphological characters, found no evidence that the Cariamidae were even close to the core Gruiformes. Cracraft et al. (2004), using about 1150 bps of the nuclear gene RAG-2 found no support for placement of the seriemas in the core gruiforms (Rallidae, Heliornithidae, Gruidae, Aramidae, Psophiidae). Fain and Houde (2004), using abut 1250 bps of the nuclear gene beta-fibrinogen, also found no support for including the Cariamidae in the core Gruiformes (same 5 families as above, the monophyly of which subsequently reaffirmed by Fain et al. 2007). Ericson et al. (2006), using ca. 5000 bp from 5 different gene regions, found that the Cariamidae were distant from the core Gruiformes (in fact, coming out near Falconidae and Psittaciformes).
Therefore, the evidence for inclusion of Cariamidae rests on historical momentum, some morphological analyses that are clearly unable to ferret out convergence (e.g., Livezey & Zusi 2007 also still firmly support a sister relationship between Gaviiformes and Podicipediformes), and a genetic analysis that has been attacked repeatedly (Sibley-Ahlquist brand of DNA-DNA hybridization). For our classification to reflect current phylogenetic data, I think we need to extricate Cariamidae [and Eurypygidae - that will be a separate proposal] from Gruiformes in that it is highly likely that continued placement there violates the primary principle of classification, namely monophyly of taxa (above species level). Therefore, in my opinion, we have to place it as an Incertae Sedis family or place it in its own order.
I might favor the former except that Cariamiformes has been used in the past. If you GOOGLE it, you get references to treatments as an order by Verheyen and Brodkorb, among others. If haven't checked out those original citations, but the point is that the name has been used, albeit sparingly, in the technical literature.
Recommendation. One could vote NO on the basis of it might be desirable to wait for one more broad study from the Early Bird and Tree of Life people. I vote YES on this one because there is no solid evidence placing Cariamidae in Gruiformes yet plenty of evidence to the contrary.
References (I have pdfs of most if you need them):
CRACRAFT, J. 1981. Toward a phylogenetic classification of the recent birds of the world (Class Aves). Auk 98: 681-714.
CRACRAFT, J., F. K. BARKER, M. BRAUN, J. HARSHMAN, G. J. DYKE, J. FEINSTEIN, S. STANLEY, A. CIBOIS, P. SCHIKLER, P. BERESFORD, J. GARCÍA-MORENO, M. D. SORENSON, T. YURI, AND D. P. MINDELL. 2004. Phylogenetic relationships among modern birds (Neornithes): toward an avian tree of life. Pp. 468-489 in "Assembling the Tree of Life" (Cracraft, J. and Donoghue, M. J., eds.). Oxford University Press.
ERICSON, P. G. P., C. L. ANDERSON, T. BRITTON, A. ELZANOWSKI, U. S. JOHANSSON, M. KALLERRSJO, J. I. OHLSON, T. J. PARSONS, D. ZUCCON, AND G. MAYR. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biology Letters 2: 543-547.
FAIN, M. G., AND P. HOUDE. 2004. Parallel radiations in the primary clades of birds. Evolution 58: 2558-2573.
FAIN, M. G., C. KRAJEWSKI, AND P. HOUDE. 2007. Phylogeny of "core Gruiformes" (Aves: Grues) and resolution of the Limpkin-Sungrebe problem. Molecular Phylogenetics and Evolution 43: 515-529.
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.
MAYR, G., AND J. CLARKE. 2003. The deep divergences of neornithine birds: a phylogenetic analysis of morphological characters. Cladistics 19: 527-553.
Van Remsen, June 2007
Comments solicited from Peter Houde: "I would add the following reference supporting gruiform monophyly:
Livezey, B.C. 1998. A phylogenetic analysis of the Gruiformes (Aves) based on morphological characters, with an emphasis on the rails (Rallidae). Phil. Trans. R. Soc. Lond. B 353: 2077-2151.
"Actually, I don't think Sibley and Ahlquist provided any evidence for gruiform monophyly. They compared gruiforms with almost nothing else. In the few cases that putative outgroups were included (1990: figs. 112-122) the melting profiles either don't appear to support gruiform monophyly or appear to be beyond the resolution of DNA hybridization. Ultimately, they assembled a supertree from small, mostly non-overlapping data sets. Gruiformes could not be anything but monophyletic in their tree because that is the way they were rooted to it.
"Everything else looks fine to me.
"Personally, I favor the use of Cariamiformes. My placement of them using the 13 loci 15kb data set is much like that of Ericson et al. Numbers on clades are Bayesian posterior probabilities and maximum likelihood bootstraps, resp., in the attached figure.
"I should add that Livezey and Zusi 2007 reconstruct Gruiformes as paraphyletic to Charadriiformes (Charadriiformes as polyphyletic within them), even though this isn't captured by their taxonomy. The nodes are 'supported' at <50-72% bootstrap."
Comments from Nores: "YES. Me parece que hay buena evidencia molecular y morfológica que esta familia no está estrechamente emparentado con Gruiformes, como lo ha hecho notar Remsen y también Houde."
Comments from Stotz: "YES. Many of these groups that are in Gruiformes are very old and the idea that they should be in separate small orders seems like it is perhaps the best approach. The idea the Seriemas are ever going to cluster strongly with some other group seems very unlikely."
Comments from Jaramillo: "YES - I must admit that it is refreshing to have so many different datasets confirm that the Seriemas are "weird," personally I have always felt this to be the case. I am swayed by Van's argument that there is no good evidence to keep the Cariamidae in the Gruiformes, so at this point there is no need to wait for another broad based paper. If new data comes out which suggests that our new arrangement is in error, we can adapt to the new data, but frankly I am reasonably convinced that this will not happen. Seriemas are weird!"