Proposal (57) to South American Classification Committee
Do not
recognize Heliangelus zusii as a valid species
PROPOSAL: Do not recognize Heliangelus zusii as a
valid species. The type and only specimen is a "Bogotá" skin without
data of any sort. In his description, Graves (1992) discards a hybrid origin
for this specimen on the grounds that no suitable combination of parents occurs
in the region of Bogotá (or central Colombia). However, the assumption that
this specimen came from near Bogotá is by no means convincing. To begin with,
"Bogotá" skins were evidently gathered over a considerable part of
central Colombia, and a number evidently came from still further afield. A
number of records for Colombia of species otherwise known only from Ecuador and
Peru are based solely upon "Bogotá" skins. This is especially
worrying given that a number of such skins, evidently indistinguishable from
"Bogotá" make, were in fact collected by Indians in Ecuador and
exported from Guayaquil, according to a conversation I had with Gustavo Orcés
some years ago at the NOC in Quito (I believe he published something on this,
but I have not yet been able to run it down). Because commerce and
communication between indigenous tribes was surely extensive in pre-Colombian
times and continued well into the nineteenth century (even before the age of
telegraph etc.), the news of such a highly profitable activity as collecting
and selling hummingbird and other small bird skins could hardly have remained a
trade secret of the tribes right around Bogotá. If this is indeed the case, a
whole new gamut of potential parents must be considered in evaluating the
possibility of a hybrid origin for this specimen. In addition, ongoing
explorations on the eastern slope of the Eastern Andes and the eastern slope of
the Central Andes in Colombia by several Colombian institutions have utterly
failed to turn up anything resembling the type of H. zusii
the only hope, so to speak, is to find a population with a distribution as
incredibly restricted as that of Eriocnemis mirabilis, but that hope is
increasingly remote. Given that there is absolutely no evidence to substantiate
the hypothesis that the lone specimen of H. zusii is a representative of
a distinct biological population, extant or extinct, I propose that its
recognition as a valid species is unjustified at this time. I should note that
the classification of H. zusii as "critically
endangered" in most modern conservation compilations is especially
unwarranted: the only category under which this bird might deserve mention in
such tomes is "data deficient".
Gary
Stiles, August 2003
Comments from Remsen: "I vote YES on this proposal
for reasons outlined by Gary above. I did not realize that Graves had
considered only central Colombian combinations. I understood that
"Bogotá" specimens could have come from anywhere in Colombia or
western Venezuela, but did not realize that Ecuador and Peru were also possibilities!
My only concern is that Graves has good instincts on this sort of thing and if
any other hybrid combinations beyond central Colombia were likely, he would
have expanded his search. Also, check out our embryonic list of Hybrid and
Dubious Taxa – Heliangelus may be the most heavily represented genus,
suggesting to me that exceptional caution must be exercised with that
lineage."
Comments from Jaramillo: "YES. Do not recognize Heliangelus zusii.
Something fishy is going on here, that is clear. The fact that there is a
single specimen and that the locality is contested, from a genus that commonly
hybridizes all say CAUTION to me."
Comments from Silva: "YES. I fully agree with
Gary's comments."
Comments from Stotz: "NO. I would like to ask
that committee members reconsider their votes on Heliangelus zusii.
While I agree that Graves, case for Heliangelus zusii is not as
strong as would be ideal, I think that given that the species has been
published and generally accepted, and is in fact treated as a endangered
species by BirdLife means that we really should not remove it from the accepted
species list without positive evidence that it is not a valid species. The
proposal states that Graves only considered possible species pairs in the
Bogota or central Colombia area, but in fact Graves (1993) says that he
considered all the trochiline species occurring in Colombia (120 species).
Given that I think some "Bogota" species are not yet certainly known
from Colombia, perhaps the search should be expanded to include Ecuador or
maybe Venezuela. But how much would that add? My estimate is that it adds 35
species, of which I can only imagine Sternoclyta cyanopectus, Hylonympha
macrocerca, and 3 species of Heliangelus as being
relevant. However, even including these species, you run up against the
argument that Graves makes in his paper. The combination of long forked tail,
shiny gorget, and blue-black plumage appears to be impossible to create by
combining two species in northwestern South America. Should we really be
treating this as dubious in the absence of a publication detailing why we think
it is dubious and without any pair of species as a possible pair? I think the
burden of proof is on those who would argue that this is not a valid species.
When I look at Graves, publications, I don't see a bias toward recognizing
doubtful hummingbirds as valid species. He has demonstrated numerous named
taxa, and unnamed specimens, are hybrids. This is not a specimen described 150
years ago by somebody who did not think about the possibility of hybrids. It
was described by the one scientist who has spent the most time thinking about
hybrid combinations in hummingbirds. In view of all that I vote to maintain H.
zusii as a distinct species until there is a stronger doubt cast on its
specific status."
Comments
from Robbins:
"After reading Doug's comments I change my vote to No on proposal #
57."
Comments
from Stiles:
"I might point out that this case [Celeus obrieni] contrasts with
that of Heliangelus zusii. The specimen of obrieni has
date, locality and collector - that of H. zusii has none of
these. The evidence for zusii being a species (or representing
a definite population at any level) is entirely negative - it doesn't look like
anything else. Doug's statement that no possible parents exist that might
account for H. zusii's being a hybrid simply doesn't wash if one
expands the search area to Ecuador and N Peru.. how about H. regalis and
another gorgeted species of Heliangelus? Or one of the latter and,
say, Eriocnemis luciani? Add to this the possibility of aberrant,
melanic phenotypes (I recently collected one such of Coeligena bonapartei,
quite strikingly different) and the picture gets still muddier. The fact that BirdLife
and some other conservation organizations have jumped on the bandwagon, so to
speak, putting H. zusii on the critically endangered or extinct lists,
seems irrelevant to the case as this determination did not involve any sort of
serious taxonomic evaluation. I emphasize that I am not saying that Graves was
wrong in describing zusii as a species, just that there is no solid,
positive evidence that he was right and certainly enough alternatives to
provide reasonable doubts on the matter. Perhaps the main point here is
philosophical: do we want to give official species status on our lists to
things that may very well not be valid taxa (at any level), just because they
do not seem to represent any extant (or extinct) taxon that is recognizable (i.
e., does represent a biological population)? Personally, I do not. I need at
least a shred or two of positive evidence - like, for instance, a definite
locality and date. These we do have in the case of Celeus obrieni. So,
on the basis of present evidence, I continue to favor putting H. zusii on
the "dubious taxa" list. I might add that if anyone does find a real
population of this hummer, I will be delighted to change my vote - but not
before!!"
Comments
from Stotz:
"Clearly there is a philosophical disagreement with respect to Heliangelus
zusii. Upon whom is that burden of proof? I will try to make this my final
diatribe on this topic. I have to agree with Gary that the fact that we don't
have a certain locality for H. zusii is a factor to be concerned about
(more on that later). The fact that BirdLife recognizes it doesn't matter
either, and I probably shouldn't have brought it up. I guess my motivation was
to indicate that H. zusii was already out there in the literature as a
valid taxon. I will admit up front that
Graves may be wrong about zusii being a valid form. However,
it is my belief that we shouldn't just shuffle a recognized species into our
dubious list. If you look at our current list, all of the species have
published literature about them, and most have a specific hypothesis as to what
they represent, such as a specific hybrid combination. Heliangelus zusii
would stand out in our dubious species list, without such. Graves did not just
take a specimen and describe it as a new species; he made an attempt to develop
an argument as to why it was a distinct species. I think that if we want to
consider zusii a hybrid, we need to directly address Graves' argument and
provide a specific alternate hypothesis (i.e. a particular pair of parental
species).
“Gary
(Stiles, that is) says that my statement that there aren't possible parental
pairs even if you extend it geographically "simply doesn't wash,"
suggesting for example that possibly H. regalis and another gorgeted
species of Heliangelus could be the parents or Eriocnemis lucianii
and another Heliangelus. My overall response to that is to say, that if
such a pair of species does exist, then it should be possible for Gary to
demonstrate that they would provide a combination that gives the characters of zusii.
He should then publish that conclusion. In terms of these specific examples, regalis
while having the body plumage, is simply too small, and though its tail is
long and forked, it is neither long enough (outer rectrix 52 vs. 67 in zusii) nor forked enough (ratio of
shortest to longest 1.80 versus 2.15). Eriocnemis doesn't provide
the body plumage characters that are needed, and although it has a long tail,
it is not nearly as deeply forked. In terms of the lack of a specific locality,
that is unfortunate, but does not directly relate to the validity of the taxon.
Several valid species were known only from Bogota specimens into the modern
age. The most notable was probably Gallinago imperialis. If a big,
relatively widespread bird like that could exist undetected by scientists for
so long, isn't it reasonable to think that H. zusii could be waiting
on some mountain slope to be rediscovered. It could however, given
deforestation in the northern Andes, have gone extinct. In that case, Gary
Stiles' test for accepting zusii as a valid species (finding a
population) will never happen.
“And
just to point out that Heliangelus zusii is not a unique case. We
recognize Popelairia letitiae, known from 3 specimens without specific
locality (Bolivia is all). My own personal favorite dubious species is Myrmotherula
fluminensis. One male specimen from Rio and the describer admitted to some
doubt.”
Comments
from Nores:
"NO. Yo coincido con los comentarios de Stotz. Aunque se
trata de un solo ejemplar de origen incierto, no se debería eliminarlo hasta
que no haya evidencias ciertas de que se trata de una especie no válida. La
larga cola furcada con los colores de lomo y garganta parecen imposible de
crear uniendo especies. Es muy importante lo que dice Stotz al último de que
Graves es un científico que ha pasado mucho tiempo estudiando hibridación en hummingbirds
y ha demostrado que muchas especies resultaron ser híbridos."
Additional
comments from Stiles:
"One last comment regarding the Heliangelus zusii situation. It has
been suggested that this is comparable to the Celeus case - I disagree. Surely a specimen with known date and
locality, from a presumably respectable collector, must count for more than a
specimen without any of these! The presumption that it is not a hybrid makes
the double assumption that all hybrids are F1's and more or less exactly
intermediate between the parental species. This is probably usually the case,
but in the case of the "Bogotá" (and Guayaquil) specimens it may not
always be so.. my impression is that some areas and species were so intensively
decimated that the survivors were willing to mate with anything remotely
resembling another hummingbird, whatever its ancestry - hence the burst of
hybridization far in excess of anything seen before or since (and all the more
explicable in a group where mating is promiscuous like the hummers). This
raises the specter of backcrosses, dominance of some genes of one phenotype,
others of another, a hybrid mating with still a third species, etc. All this,
coupled with the total lack of data of the specimen, creates enough doubts (to
me) to place this form on the "dubious taxa" list. I emphasize that
Graves MAY be correct in calling it a species - I personally would be delighted
if a population were found - but without more, solid data, such as a specimen
with proper data, I cannot bring myself to call this critter anything other
than a "dubious taxon".