Proposal (560) to South American Classification Committee

Add “Tribes” to classification where warranted

Effect on SACC list: If this proposal passes, the “tribe” level of classification would be adopted in those cases in which well-sampled subfamilies show major, deep lineages within them.

Rationale: I personally find it increasingly useful to have formal taxon names to label strongly supported nodes in a densely sampled subfamily. The tribe level of classification is used in many classifications, including by our sister committee, NACC, for North American birds, and by the Handbook of the Birds of the World series. The forthcoming revision of Dickinson (2003) will use them to a much greater degree.

A laborious discussion of the pros and cons of the Linnaean categorical scheme is beyond the scope of this proposal. The glaring absence of objective definitions of the higher-level categories that are already in widespread use (order, family, subfamily) handicaps any real discussion of what a tribe would be other than two or more monophyletic groups within a subfamily for which strongly supported nodes identify divergent lineages. Best to use an example. In the Trochilidae, we currently recognize three subfamilies. However, the McGuire et al. data show that the subfamily Trochilinae consists of multiple, strongly divergent lineages that might/could/should be recognized taxonomically. Certainly, the categorical minds of us humans find these labels useful for discussions, as we did in those McGuire et al. phylogenies.

Clearly, taken to the extreme, every strongly supported node in a phylogeny could be given a name, and so we have to be careful how far we go. However, in this case, the tribe level is in widespread use in ornithology, so we’re not breaking any new ground.

Recommendation: YES: the minimal “cost” of adding an additional hierarchical level to our classification, on a careful case-by-case basis, is offset by the benefit of upgrading the information content of a classification and linear sequence, in my opinion.

Van Remsen, October 2012

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Comments from Zimmer: “YES, for reasons stated by Van in the proposal.  The fact that this category is already used by the NACC and by HBW adds some additional impetus as far as I’m concerned. Better that we are all on the same page with this.”

Comments from Stiles: “A qualified YES., as above, only if the evidence from multiple genes notably nuclear ones) is consistent - otherwise, going overboard with tribes now might only make more work for the future as new studies add possibly conflicting information.”

Comments from Nores: “NO, definitely. After 15 years of SAAC and when it should end, we cannot start now with tribes, superfamilies, subspecies or other categories. This is already defined.”

Comments from Robbins: “NO, consistent with my comments made concerning the utility of subfamilies. When examining a tree, tribe/subfamilies are totally superfluous for understanding and communicating relationships. Why interject yet two additional layers of nomenclatural subjectivity?”

Comments from Stotz: “YES. I hope we won’t overdo it, but tribes are useful in big intrafamilial units, think Ducks and Sandpipers, and probably Hummingbirds and maybe Flycatchers, Tanagers, Furnariids etc.”

Comments from Pacheco: “YES. I see advantages in using Tribes, but only in certain well-sampled subfamilies.”

Comments from Pérez-Emán: “NO. Although the use of these categories could be useful to summarize potential phylogenetic information, I am concerned, as I was when commenting on the subfamily proposals, on the subjectivity and lack of stability that could be associated with each proposal evaluation. Studies on the same group but with different set of characters could lead to different classifications, as well as those with different levels of taxon sampling. Just as an example, the Accipitridae studies of Lerner & Mindell (2005) and Griffiths et al. (2007) are not 100% congruent in the resolution of nodes candidates for the level of tribe. Another important question, and not less important, is what to do with those groups of birds not densely sampled. Should we pursue a classification with tribe categories for some taxa and not for others? How would it be interpreted (for the user)? It could be misleading by “indicating” a lack of phylogenetic structure for such groups (at that level).”

Comments from Cadena: “NO. My opinion on this is the same that I presented under proposal 552 for the issue of recognizing subfamilies. But recognizing tribes is a bit too much - are we going to go through all the trouble of recognizing such categories across all our classification? If yes, this would be a rather difficult task and I do not know whether people will use such tribes. If no, then we will end up with an inconsistent classification in which tribes are recognized in some clades but not in others.”