Proposal (126) to South American Classification Committee

 

Move Coereba, Tiaris, and Galapagos "finches" to Incertae Sedis

 

Effect on South American CL: This proposal changes our linear sequence by taking removing the deletes the family-level taxon Coerebidae from our classification and placing its sole species, Coereba flaveola, next to (before) Tiaris olivacea, and then moving all of the "dome nest" clade to Incertae Sedis.

 

Background: We have already voted to delete the family-level taxon -- see Proposal #98. Now, we must decide where to move Coereba flaveola.

 

The choices for placement of this species within the existing linear sequence are few and ugly:

 

(a) move Coereba into our current Emberizidae next to Tiaris [minimum "disturbance" to classification but maximum perpetuation of a classification that maintains polyphyletic Emberizidae].

 

(b) placement of Coereba and all other taxa in this group in Incertae Sedis category in nine-primaried oscines.

 

(c) placement of Coereba and all other taxa in this group in the Thraupidae [probably most consistent with current genetic data].

 

New information: Two genetic data-sets (Sato et al. 1999, Burns et al. 2002, 2003) now show that Coereba is embedded in a clade of "island" taxa, most of which were formerly classified as sparrows (Emberizidae/Emberizinae): Euneornis, Loxigilla, Loxipasser, Melanospiza, Melopyrrha of the West Indies, Tiaris of primarily the Caribbean Basin, and all of the Geospizinae (Galapagos finches). Based in 1045 bp of cytochrome b, the bootstrap support value for this clade (parsimony /PAUP) in Burns et al. (2003) is 98%; the same group is supported by a 100% posterior probability value in a Bayesian analysis. Based on ca. 2000 bp of cytochrome b, plus ca. 1500 bp of numt2and numt3, in Sato et al. bootstrap support for this group was 74% (parsimony/PAUP) and 77% (maximum likelihood/PAUP); Sato et al. did not have as complete a taxon-sampling as Burns et al. for the non-Galapagos taxa, but had more geospizines, including Pinaroloxias of Cocos Island.

 

Within this clade, Burns et al. (2003) found modest Bayesian posterior probability support (90%) and weak bootstrap support (52%) for a sister relationship between Coereba flaveola and Tiaris olivacea. (Tiaris fuliginosa and T. bicolor come out in different sections of the clade, so it is likely that this genus is polyphyletic.) In Burns et al.'s Fig. 2, a strict consensus tree, most nodes within the "dome nest" clade that includes these taxa plus Galapagos finches, Loxigilla, etc., collapse. Therefore, strong conclusions on relationships that would allow confident changes in linear sequence within this group seem absent, and the prudent course would be not to rearrange any taxa within this group, as long as they are all listed consecutively.

 

Analysis: Moving Coereba next to Tiaris would seem to be the only viable option. In our sequence, that would mean Coereba flaveola comes first, followed by Tiaris olivacea and rest of Tiaris. The problem arises after this move is made. Thus, this proposal will concentrate on where this group should go rather than where Coereba itself should go.

 

Currently, Tiaris and the dome-nest group are in Emberizidae if all we do is move Coereba, yet evidence is mounting for them being within Burns's true Thraupidae. Nonetheless, if you collapse nodes in Burns et al.'s Fig. 1 that have less than 90% Bayesian support, there is still a chance that the dome nest clade will fall outside the Thraupidae. Likewise, in Fig. 2, the branching pattern largely dissolves at bootstrap values below 75% to the point of becoming a large polytomy. Thus, I think it is not wise to move the dome-nesters into Thraupidae until Kevin publishes additional data.

 

Thus, this leaves us, in my opinion, with a choice between options (a) and (b) above.

 

Kevin himself favors placing Coereba next to Tiaris but leaving them in Emberizidae. Here is what he emailed me:

 

"You are right that it will maintain a polyphyletic Emberizidae. However, I imagine there are lots of other taxa in the check-list's Emberizidae that are most closely related to members of Thraupidae. (i.e., what have you done with all the South American finches that Sibley wanted to move to his Thraupini?) If those are still all in Emberizidae, it may be best just to keep Coereba et al. in the Emberizidae. In a couple years, we should have our complete 9-primaried oscine phylogeny done. You might want to wait until then to really sort out what, if anything, is Thraupidae.

 

"I wouldn't favor putting them into an Incertae Sedis category because it implies they are somehow distinct from other tanagers and tanager-finches. There are probably many taxa that should be put in incertae sedis, I don't see why we should single out this group."

 

These are good points, and so what I will do if this proposal passes is do a second proposal to "cleanse" our current Emberizidae of all the probable tanager-relatives, e.g., Catamenia, SicalisSporophila, and so on, based on Kevin's and Bledsoe's published genetic data. We already have an Incertae Sedis category in the 9-primaried oscines, so the way is paved. It may be unsettling that the I.S. category may soon have more species in it than any of the families themselves, but this is fine with me -- it sends a dramatic signal to everyone that the boundaries between Emberizidae, Thraupidae, Parulidae, and Cardinalidae are uncertain, and it leaves those families with a minimal number of taxa that do not belong there, improving the chances that each is a natural group. In the Notes, we can point out the likely final "destination" in terms of family assignment, with citations to appropriate papers, as we already do for Piranga and so on.

 

Recommendation: I do not feel strongly about any of these options, but I have a mild preference towards sending the whole group to Incertae Sedis status. This highlights the uncertainty, draws attention to the problem, and avoids a likely erroneous assignment of the group to Emberizidae (whatever that turns out to be). The disadvantage is that the dome-nesters are just one of several groups that could and probably should be deported from Emberizidae based on Burns et al. and others, and so one could correctly dispute singling out just the dome-nesters. As noted above, I can fix that with a subsequent proposal to deport other taxa from Emberizidae to I.S.

 

Literature Cited

BURNS, K. J., S. J. HACKETT, AND N. K. KLEIN. 2002. Phylogenetic relationships and morphological diversity in Darwin's finches and their relatives. Evolution 56: 1240-1252.

BURNS, K. J., S. J. HACKETT, AND N. K. KLEIN. 2003. Phylogenetic relationships of Neotropical honeycreepers and the evolution of feeding morphology. J. Avian Biology 34: 360-370.

SATO, A., C. O'HUIGIN, F. FIGUEROA, P. R. GRANT, B. R. GRANT, H. TICHY, AND J. KLEIN. 1999. Phylogeny of Darwin's finches as revealed by mtDNA sequences. Proc. Nat. Acad. Sci. 96: 5101-5106.

 

Van Remsen, May 2004

 

======================================================

 

Comments from Stiles: [YES] "Although I donęt like "incertae sedis" for Coereba et al., I'll vote yes on the proposal - I do hope that something gets sorted out better before we go to press with the checklist!!! If nothing else, it points up the fact that the traditional bill-foot taxonomy has led to numerous "embarradas" in the 9p oscines! My second choice would be to stuff 'em all into Emberizidae and acknowledge that it's a bit of a grab bag, pending more data from the DNA boys."

 

Comments from Robbins: [YES] "I'm not wild about dumping this group into incertae sedis as we will soon (I hope) have to deal with them again. However, I guess it is better than leaving Coereba in its own family when it is clearly embedded within the Caribbean seedfinch clade. Thus, I vote "yes" to the proposal."

 

Comments from Silva: "YES. Although I do not like "incertae sedis", I think that we can apply in this specific case and wait for more detailed phylogenetic information about Coereba group."

 

Comments from Zimmer: "I vote "YES" for reasons stated by Van and others. I think it is just as important for our checklist to highlight what isn't known, as it is to highlight what is known. Better not to perpetuate or create more problems by sinking the clade into Emberizidae -- that will only further muddy the waters. Better to isolate the group and cast light on it, even if it means saying that we don't know what to call it."

 

Comments from Jaramillo: "NO. I am going with a no, but hesitantly. It seems equally valid to keep in the Emberizidae, and publish with copious notes as to why this is not satisfactory. I do hope that this becomes resolved before publication time; many users of the checklist will be more annoyed and confused with Incertae sedis than the incorrect placement in Emberizidae. Besides, the Emberizidae has so many "embarradas" as Gary calls them that one more for the time being does not trouble me."