Proposal
(87) to South American
Classification Committee
Treat
the taxon terborghi as a subspecies of Atlapetes rufinucha
Effect on South American
CL: This proposal would lump two taxa that we treat as
separate species into Atlapetes melanolaemus (or into a
single, more traditional Atlapetes rufinucha, pending outcome on #86).
Background: The
taxon terborghi was described by Remsen (1993) as a subspecies
of the broadly defined A. rufinucha. It is endemic to the
Cordillera Vilcabamba in depto. Cuzco, Peru. Terborghi stands
out from any taxon in the former A. rufinucha complex in being
greener and darker ventrally. It shares with A. melanolaemus (s.
Cuzco to n. La Paz; not parapatric with terborghi "because"
they are separated by A. canigenis) an absence of loral spots and
an extension of the chestnut crown to the bill (not separated by black, as in
nominate rufinucha), but differs in lacking the dark breast
markings of melanolaemus and in having at least a small black
"whisker" mark. It further differs from nominate rufinucha in
having a less conspicuous "whisker". It differs from both melanolaemus and
nominate rufinucha in having a slightly paler back, showing
some contrast with head. There are no comparative data on vocalizations.
New information:
García-Moreno & Fjeldså (1999) found that the "species" Atlapetes rufinucha was
polyphyletic, with the northern form, A. latinuchus, more closely
related to nominate A. schistaceus than to A.
rufinucha. This was based on a very small (275 bp) portion of the
cytochrome-b gene, and the bootstrap values are unimpressive (and I doubt that
these results would be publishable in 2003). Nevertheless, their resulting tree
shows sufficient geographic structure, with adjacent Atlapetes usually
appearing as sisters, so I suspect that many of the results will hold up with
larger data sets.
They did not have tissue
from terborghi but ranked it at the species level with the
following statement:
"The four forms [canigenis,
terborghi, melanolaemus, melanopis] constituting the 'central branch' could
be treated as polytypic species. However, each of the constituent forms is more
distinctive (morphologically and by mtDNA divergence) than many other
brush-finches currently admitted species rank. Although we fail to recognize
physical barriers that could separate terborghi, canigenis, and melanolaemus,
we know of no evidence of intergradation between them."
One could easily find
fault with portions of this reasoning, especially given the presumed isolation
of terborghi and the lack of a DNA sample from it.
Analysis: The
data for species rank of terborghi are weak. Nonetheless, the
argument could be made that terborghi is at least as
distinctive phenotypically as melanolaemus and nominate rufinucha are
from each other, and so if melanolaemus is treated as a
species, then certainly terborghi should also be so treated. On the
other hand, it is more difficult to justify treatment of terborghi as
a separate species from A. melanolaemus, but they do differ more
dramatically in color of the underparts than any Atlapetes taxa
currently treated as conspecific.
Recommendation: I
tentatively vote NO on this one (i.e., stick with current classification).
Although the evidence is weak for species rank of terborghi, I
suppose that the "burden of proof" in this falls on the case for
considering it conspecific with Atlapetes melanolaemus or A.
rufinucha, or making a change from our current classification.
Literature Cited:
GARCÍA-MORENO,
J., AND J. FJELDSÅ. 1999. Re-evaluation of species limits in the genus Atlapetes based
on mtDNA sequence data. Ibis 141: 199-207.
REMSEN,
J. V., JR. 1993. Zoogeography and geographic variation in Atlapetes
rufinucha (Aves: Emberizinae), including a distinctive new subspecies,
in southern Peru and Bolivia. Proc. Biol. Soc. Wash. 106: 429-435.
Van
Remsen, December 2003
__________________________________________________________________________
SACC voting chart
proposals 1-99
Comments from Stiles:
"[NO]. I agree that the evidence is not overwhelming, but it is a shade
better than the evidence for the contrary - and solid contrary evidence should
be forthcoming to change the "status quo". NO to both (maintain
species status, at least for now)."
Comments from Zimmer:
"[NO] Once again, the evidence for maintaining as separate species is
weak, but I vote "NO". Maintaining our current status quo is at least
consistent with how other forms in the genus are treated."
Comments from Robbins:
"[NO] To be consistent with my vote in proposal # 87 I vote
"no". Given the evidence at hand we can't treat melanolaemus as
a species and not terborghi."
Comments from Stotz: "YES,
for lumping all of these into rufinucha. I have to say that I
hardly consider the splitting of these species as the "status quo."
To me the status quo is the broad rufinucha, which we had until
1999. Van is correct to point to the short piece of DNA used in the
Garcia-Moreno and Fjeldså study and to note the weak support for the taxa that
they suggest. There are only two branches with over 50% bootstrap support. They
support a northern clade, and a sister relationship between rufinucha and fulviceps.
I am willing to overlook this because of the shortness of the segment of DNA
that was studied. My personal feeling is that we would be better off
with the original 4 species (schistaceus, rufinucha, rufigenis
and tricolor) with the recognition that there are problems that need to
be solved, but as that is not currently on the table, I don't think placing
terborghi, melanolaemus and rufinucha into a
single species conflicts with any of the results of the 1999 in a significant
way. Terborghi and melanolaemus occupy
basically adjacent areas to canigenis, but only if you believe the
poorly supported results and believe that species have to be monophyletic is
that a problem. Finally, I have to say that it seems strange to me that we
completely follow the novel arrangement suggested based on very weak data for
these brush-finches, while Poospiza whitii and Hyloctistes
virgata are not split."
Comments from Jaramillo:
"NO -- partly to be consistent with 86, but even more reluctant in this
case."
Comments from Nores: "NO, yo estoy de acuerdo de considerar a Atlapetes
terborghi como una full especie. Es un caso muy similar al de la
propuesta 86."
Comments from Schulenberg:
"YES. My sentiments as per Doug's."