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".