Proposal (#378) to
Recognize Trogon caligatus as a separate species from Trogon violaceus (2)
Effect on SACC: This would treat an existing species, Trogon violaceus, into two species.
Background: Our current SACC note is as follows:
8. The subspecies ramonianus and caligatus were formerly (e.g., Cory 1919, Pinto 1937) considered separate species from Trogon violaceus, but Peters (1945) considered them all conspecific. Ridgely & Greenfield (2001) considered caligatus of Middle America and northwestern South America to be a separate species from Trogon violaceus, and this was followed by Hilty (2003); SACC to recognize this split did not pass because of insufficient published data. Genetic data (DaCosta & Klicka 2008) indicate that caligatus is basal to a group that includes Amazonian T. violaceus, T. curucui, and T. surrucura (and that Amazonian violaceus may be paraphyletic with respect to the latter two species). Proposal needed.
See SACC proposal for a summary of previous arguments pro and con. A one-sentence summary of the previous arguments might be although differs from in voice and plumage, the vocal differences have not been adequately quantified or documented; also, the plumage differences do not divide so cleanly the constituent populations.
New information: DaCosta & Klicka (2008) published a gene-based phylogeny of the genus that included samples of caligatus (N=9) from Mexico, Honduras, Costa Rica, and Panama, as well as, I think, W Ecuador (a sample from “eECU” is presumably a typo for “wECU”), nominate violaceus from the Guianan Shield (N=2), and Amazonian ramonianus (N=4) from Ecuador, Peru, Venezuela, and Bolivia. They sampled 1 mitochondrial gene, ND2, and 1041 base pairs, of which 557 were phylogenetically informative.
They found that their three groups fell into three clades: (1) caligatus was basal to a group of taxa that included not only the other violaceus samples but also T. curucui and T. surrucura, with strong support (100% maximum likelihood bootstrap, 100% Bayesian support); (2) nominate violaceus and T. curucui are sisters, also with strong support (100% maximum likelihood bootstrap, 100% Bayesian support); and (3 Amazonian ramonianus is the sister to group 2 (83% maximum likelihood bootstrap, 86% Bayesian support).
Analysis and Recommendation: With genetic support from only a single, mitochondrial gene as the basis for the relationship, one could argue that the tree is only a gene tree, not a species tree, or that incomplete lineage-sorting confounds the result. However, with the qualitative vocal data, I think that published evidence is sufficient for a change in species limits, so I tentatively recommend a YES. From the plumage and genetic data, one could also make a case that ramonianus should also be elevated to species rank, but I think this should await more detailed vocal analyses as well as sampling crissalis from E Brazil.
DaCOSTA, J. M., AND J. KLICKA. 2008. The Great American Interchange in birds: a phylogenetic perspective with the genus Trogon. Molecular Ecology 17: 1328-1343.
Note on English names: Ridgely & Greenfield (2001) coined “Northern Violaceous Trogon” for caligatus and “Amazonian Violaceus Trogon” for viridis, and this was followed by Hilty (2003). However, Cory, Ridgway, and other authors of that era used “Gartered Trogon” for caligatus, leaving Violaceus for violaceus, and this was, most notably, followed by Gill & Wright (2006). I like these simpler names, which also avoid the irksome need to hyphenate “Violaceus-Trogon” under the AOU system. Also, those long compound names are fairly unpopular, despite their ability to imply relationships. And in this case, with none of the component taxa likely each other’s sister, they are actually misleading as to relationships. Finally, “Northern” and “Amazonian” are fairly insipid. Therefore, I propose we use these shorter, more accurate, more venerable names as the status quo (therefore requiring a proposal the longer compound names could be instituted by proposal), but I’d like to take a poll of our English-first members to see if they like this.
Van Remsen, November 2008
Comments from Zimmer: “YES, on the basis of genetic and plumage data, combined with qualitative vocal data. However, I would go further and strongly suggest that ramonianus, together with crissalis, constitutes a species distinct from both nominate violaceus and the caligatus group of Central America and trans-Andean western South America. The DaCosta & Klicka paper presents genetic data backing such a treatment for ramonianus, which, in my experience, is the most vocally distinct taxon in the entire group. There is no published vocal analysis to prove this, but there are published qualitative descriptions, as well as published sample recordings of nominate violaceus, the caligatus group, and ramonianus/crissalis. Examples are also searchable online at the Macaulay Laboratory website (probably also at Xenocanto). For example, go to the site, and do a search for Trogon violaceus recordings. Check out LNS recordings #38963 (Ted Parker recording from Pando, Bolivia) and #11364 (Curtis Marantz recording from Amazonas, Brazil), both of which are representative of ramonianus. You will see that the notes of the song have a diphthongal or nearly bisyllabic quality. This squares with the description of the song of “Amazonian Violaceous Trogon” in Ridgely & Greenfield’s Birds of Ecuador, which the authors describe as “a fast but relatively short series of clipped “cow” notes, the notes often becoming doubled (“cadow-cadow-cadow..”).” This is in marked contrast to not only the songs of trans-Andean caligatus, but also to Guianan/n Amazonia east of the rio Negro nominate violaceus, both of which sound much more like Blue-crowned Trogon (T. curucui) in having a longer, faster series of higher-pitched notes which are more reminiscent of the song of Ferruginous Pygmy-Owl (Glaucidium brasilianum). Again, compare the two LNS recordings of ramonianus noted above to any LNS recordings of nominate violaceus from the Guianan region, or to any recordings of the caligatus group from Central America or western South America. In my experiences, the differences noted (bisyllabic or diphthongal notes, fewer notes per song, slower pace and lower pitch for ramonianus versus single-syllable notes, many more notes per song delivered at faster pace and higher pitch for nominate violaceus) are absolutely consistent throughout their respective ranges. Songs of crissalis, although possibly not identical to those of ramonianus, are at least distinctly similar, and are noticeably different from those of nominate violaceus. I would argue that the available genetic, morphological and vocal evidence for splitting ramonianus/crissalis from nominate violaceus is at least as solid as the evidence for splitting the caligatus group from nominate, and that the vocal differences are much greater between ramonianus/crissalis and nominate, than between nominate and the caligatus group. (Caution: Do not be misled by some of the purported violaceus LNS recordings from Mato Grosso, Brazil, which sound like north bank (nominate) violaceus. I am certain that these represent misidentifications of the songs of Trogon curucui, an easy and natural error for observers familiar with the songs of violaceus from Central America or the Guianan region to make. In each such recording that was accompanied by a voice announcement, the recordist reported the recorded bird as unseen, but thought to be violaceus.)
“As regards English names, I think Van’s suggestions of “Gartered Trogon” for the caligatus group and “Violaceous Trogon” for nominate, are excellent. HBW lists “Amazonian Trogon” as a name available for ramonianus, and I think that would be appropriate for the combined ramonianus/crissalis.”
Comments from Robbins: “YES, as one can readily hear by making vocal comparisons between these taxa on the Macaulay LNS and Xenocanto America websites, coupled with the Klicka et al. genetic data makes this a straightforward decision.
“In addition to recognizing caligatus as a species, I fully support taking this a step further, as Kevin suggests, and recognizing ramonianus/crissalis as a species. Finally, I not only support Van’s English name suggestions for caligatus and nominate violaceus, but Kevin’s suggestion of Amazonian Trogon for ramonianus/crissalis.
Comments from Stiles: “YES. With genetic evidence in hand that corroborates the differences in morphology and vocalizations, the burden of proof now falls heavily upon the lumpers. Regarding Kevin’s suggestion to split ramonianus/crissalis, he might well be right but I would prefer to see this as a separate proposal, where more detailed arguments can be brought to bear.”
Comments from Nores: “YES. Los datos genéticos, morfológicos y de vocalizaciones muestran claramente que se trata de una especie diferente de T. violaceus. Lo que si, esto implica que las subespecies sallaei y concinnus de Mexico y Centro América pasan a ser subespecies de T. caligatus. Por las mismas razones, y por los datos aportados por Zimmer estoy de acuerdo en considerara ramonianus-crissalis como una especie diferente de T. violaceus.”
Comments from Cadena: “YES. Kevin's point on ramonianus etc. is also well-taken (I assume this will become a separate proposal).”
Comments from Stotz: “YES. I am pretty convinced by Kevin's discussion of violaceus versus ramonianus along with the genetic work that these should be split, but I think we should have a separate proposal for it. I favor Van's English names.”
Comments from Jaramillo: “YES – Song, morphology and genetics all line up to clarify the relationship here. I look forward to another proposal for ramonianus, as that does indeed sound different. Also Yes on Violaceous and Gartered trogons.”
Comments from Pacheco: "YES. Em concordância com os dados apresentados e comentários aqui expostos.”