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, Sicalis, Sporophila, 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 donĀ“t 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 9-p 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."