Proposal (#64) to South
American Check-list Committee
Treat Myioborus castaneocapillus
as a separate species from M. brunniceps
Effect on South American CL: This proposal would
split our Myioborus brunniceps into two species, with recognition of
northern castaneocapillus* as a separate species.
Background: The bird we treat as one species, Myioborus
brunniceps (Brown-capped Redstart), has a disjunct distribution, with one
subspecies group in the Tepui region of Venezuela and the other in the Andes
from central Bolivia to central Argentina and the mountains of Córdoba. This
follows the traditional classification (e.g., Hellmayr 1935, Meyer de
Schauensee 1966, 1970, Lowery & Monroe 1968, Meyer de Schauensee &
Phelps 1978).
The subspecies castaneocapillus is very
similar in plumage to brunniceps, differing primarily in amount of white
in face, but the subspecies duidae at least superficially looks more
similar to M. cardonai of Cerro Guaiquinima than it does to castaneocapillus.
New information: Ridgely & Tudor
(1989) considered the three northern subspecies as a separate species, M.
castaneocapillus (with duidae and macguirei) from M.
brunniceps. This was based in part on the highly disjunct distribution, but
also on differences in the song. They described that of the castaneocapillus
group (subspecies not specified) as "a thin unmusical chipper, starting
slowly, gradually speeding up and descending in pitch," whereas that of brunniceps
was described as "an even, fast, thin, sibilant trill with slight
crescendo effect." Curson et al. (1994), Sibley & Monroe (1990), and
Hilty (2003) all followed this and elevated castaneocapillus to species
rank. Hilty (2003) gave a similar description of the song of subspecies castaneocapillus
that is similar to that given in Ridgely-Tudor, but also added "Less
often gives rather slow, warbling trill, colorless and more like others of genus";
the songs of M. cardonai and M. albifacies evidently remain
unknown.
Analysis: Based on geography, I predict that the castaneocapillus
group is genetically closer to the allotaxa cardonai and albifacies,
both traditionally ranked as species, than to distant brunniceps; and
this will provide yet another example of an emerging pattern, namely
"breakout species" that are phenotypically different from any
population of a widespread species but genetically closer to nearest population
of the widespread species than populations within that widespread species are
to one another. Ridgely & Tudor (1989) suspected that cardonai and albifacies
were best treated as conspecific, pointing out that their main differences, in
crown and face color, are plastic characters within other Myioborus taxa
treated as conspecific, e.g., M. melanocephalus. These taxa all appear
to form a superspecies (and Sibley & Monroe also include M. pariae
in this superspecies).
Recommendation: I reluctantly vote "NO" on this proposal.
Predictions and instincts are not sufficient for making decisions. This is
another example of what is almost certainly a "correct" taxonomic
decision based on substandard published data (e.g., Hyloctistes
proposal). Although I bet that Bob and Steve Hilty have it "right," I
do not think that the published data are sufficiently strong for a change from
historical status quo. To make official changes, I hope that we require more
rigorous evidence than a couple of qualitative descriptions of songs (of notoriously
variable parulids no less). South American Myioborus represent a complex
taxonomic situation that, in my opinion, needs a thorough overall study, before
we make isolated changes; even so, I could be persuaded to do a piecemeal
change if a short paper with sufficient Ns of sonagrams were published.
* Correct spelling is
castaneocapillus, not castaneocapilla (David & Gosselin
2002a).
Literature Cited:
CURSON, J., D. QUINN, AND D. BEADLE. 1994.
Warblers of the Americas. Houghton Mifflin.
HELLMAYR, C. E. 1935. Catalogue of birds of the
Americas. Field Mus. Nat. Hist. Publ., Zool. Ser., vol. 13., pt. 8.
HILTY, S. L. 2003. Birds of Venezuela.
Princeton University Press, Princeton, New Jersey.
LOWERY, G. H., JR., AND B. L. MONROE, JR. 1968.
Family Parulidae. Pp. 3-93 in "Check-list of birds of the World, Vol.
14" (Paynter R. A., Jr., ed.). Museum of Comparative Zoology, Cambridge,
Massachusetts.
RIDGELY, R. S., AND G. TUDOR. 1989. The birds
of South America, vol. 1. Univ. Texas Press, Austin.
SIBLEY, C. G., AND B. L. MONROE, JR. 1990.
Distribution and taxonomy of birds of the World. Yale University Press, New
Haven, Connecticut.
Van Remsen, October 2003
Comments from Stotz: "YES. I
recognize that this is not the best-established split, but it is hard to imagine
that castaneocapillus has anything to do with brunneiceps.
Perhaps more to the point, the basis for any treatment of Myioborus is
very weak. It is purely historical accident that we consider brunneiceps
and castaneocapillus conspecific while pariae is a distinct
species. Peters (Vol. 14) refers you to the Phelps' Venezuelan list for reasons
for treating pariae (described as a subspecies of brunneiceps) as
a distinct species. All that the Phelps' say is "Por los disenos
distintivos de la cabeza de la cola creemos que debe ser considerada como una
especie." I would suggest that Ridgley and Tudor's vocal descriptions
combined with the fact that brunneiceps is at the southern end of the
Andean chain, while castaneocapillus is a Tepui endemic with ties to montane
forms in Venezuela (that we treat as separate species) is a stronger argument
for status as a separate species than stronger yellow rather than white facial
markings and more white in the tail (characters for pariae)."
Comments from Robbins: "[YES] I have
field experience with only castaneocapillus (from Roraima), but I do
agree with both Ridgely and Hilty's description of the song of castaneocapillus.
I have no doubt that Bob accurately described the song of brunniceps.
Finally, from a biogeographical standpoint the split makes sense. Hence, I vote
"yes".
Comments from Schulenberg: "My vote is YES.
Jorge Perez (now, I believe, back in his native
Venezuela) did a great study of Myioborus (Molecular systematics,
biogeography, and population history of the genus Myioborus [Aves, Parulinae])
for his doctoral thesis (2002, University of Missouri-Saint Louis).
Jorge had excellent taxon sampling (21, I
think, taxa of Myioborus) and utilized three mitochondrial genes
(cytochrome b, ND2, ND3), with a little over 2500 base pairs combined. His
trees are well resolved. Based on Jorge's results, brunniceps is basal
to a widespread clade of upper montane Myioborus; castaneocapillus
is nested well within the clade, and is separated from brunniceps by
several other taxa. Clearly these are different species, as would be expected
by geography and is consistent with the other, more limited information.
Normally of course I hold firm for a
"publication" as the basis for our revisions to the base list. Jorge
may have a paper on his results already submitted or in press, I don't know.
But the research has been done, it has been written up (at least in thesis
form), and it seems silly to me to pretend that it does not exist. Jorge has
given at least one talk at an American Ornithologists' Union (perhaps at more
than one meeting), he's given invited seminars on his research, and so his work
is becoming known. His thesis is something that we can cite (if he doesn't have
something in press already), and enterprising types can track down a copy. Of
course, if he publishes his phylogeny, then that would not be necessary. In the
meantime, there is a copy of his thesis at Field Museum, and if necessary I can
send copies of some or all of it to anyone on SACC who is interested. Chapter
headings are Moleculuar phylogenetics and biogeography of the genus Myioborus
(Aves, Parulinae); Biogeographic patterns in the Pantepui region: inferences
from mtDNA phylogeography of Myioborus castaneocapillus (Aves:
Parulinae); and Patterns of avian geographic differentiation in Neotropical
montane habitats: a mitochondrial DNA phylogeographic study of the Myioborus
miniatus (Aves, Parulinae) complex."
Comments from Jaramillo: "YES. I have a lot of experience with brunniceps
and was astounded to see how different castaneocapillus looked and acted
in the field when I saw this taxon. For one castaneocapillus looked
darker and grayer to me, and I recall that it looked large (not sure if
measurements bear out this difference). However, I do recall hearing some
songs, which were quite different from the very high-pitched, even trill (can
recall Blackpoll) of brunniceps. These field impressions are just that
impressions but they certainly move my gut to the split side on this issue, add
to this the data that Tom mentions exist and I am perfectly comfortable
accepting this change. Theses are stored and archived, while not peer-reviewed
publications they are available and we can cite the specific thesis in this
case."
Comments from Zimmer: "I vote
"YES". Besides the range disjunction and vocal differences, the Jorge
Pérez thesis does give us something to hang this change on, even if it isn't
published in the traditional sense."
Comments from Nores: "YES. Yo solo tengo experiencia con brunniceps, pero parece evidente que,
por distribución geográfica, coloración, canto y sobre todo genética (de
acuerdo a los datos de Jorge Pérez mencionados por Schulenberg), son especies
diferentes."