Proposal to South American Classification Committee
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Reorganize the generic classification of the “core tanagers” Proposal (437) to South American Classification Committee Several genetic studies have consistently identified a large clade of the Thraupidae (including nearly 100 species, at least a third of the Thraupidae, depending upon where family limits are eventually fixed), including the type genus Thraupis, the very large genus Tangara, and a diverse group of more-or-less montane genera (Yuri & Mindell 2002, Burns et al. 2002, Burns & Naoki 2004). For convenience, Burns & Naoki called this clade the “core tanagers”. Sedano & Burns (2010) have now produced a nearly complete phylogeny of this clade (including all current genera and 93 of 99 current species). This phylogeny is based upon large (1000+base pairs) samples of two mitochondrial genes and is rooted by the “Tholospiza” group (Coereba, the geospizine finches and several West Indian finches that have been identified as embedded in the Thraupidae and the closest relatives of the “core tanagers” in some studies. The Sedano & Burns study produced a consistent, mostly well-supported tree with Bayesian and maximum-likelihood analyses that, if accepted, would require considerable modifications in the current generic classification of the “core tanagers”. Sedano & Burns made a number of recommendations based on this tree, but these tended towards lumping of many distinctive groups into a few, highly heterogeneous and virtually non-diagnosable genera. The object of this proposal therefore is to seek a compromise solution that maintains genera as monophyletic groups while at the same time maintaining diagnosability with the least possible disruption of the current nomenclature. Even with these guidelines, it is evident that a considerable number of generic changes will be required. For the recommendations I propose, I have relied principally on the synonymies in Hellmayr (1936) and Ridgway (1911). I will divide the proposal into several parts, following the phylogeny of Sedano & Burns: 1) the Tangara group; 2) Chlorochrysa and the Paroaria clade; and 3) the mountain tanager clades. 1) The Tangara group: among the surprising results of the Burns & Sedano study is that Tangara, considered a monophyletic group by Burns and Naoki (2004), is actually polyphyletic with respect to Thraupis. Although the overall species groupings in Tangara itself found by Burns & Naoki were supported, Thraupis (itself polyphyletic) was found to be embedded in Tangara by Sedano & Burns. This would require either lumping the “true” Thraupis into Tangara to form a huge, heterogeneous genus, or splitting up Tangara into several smaller, monophyletic genera while maintaining a monophyletic “true” Thraupis that morphologically seems decidedly out of place in Tangara. Here I pursue this alternative and recommend the following generic arrangement. a) Tangara Brisson 1760: the “true” Tangara comprise a large group of 26 species, the type of which is brasiliensis (now considered a subspecies of T. mexicana). The species included are those from vassorii through seledon in the phylogeny. This clade includes several subclades that could be split off if one wishes to maintain relatively homogeneous branch lengths throughout. This would require splitting Tangara into at least five smaller genera: Procnopis Cabanis 1844 for vassorii through fucosa in the phylogeny; a new genus for cyanotis and labradorides; Gyrola Reichenbach 1850 for gyrola and lavinia; Chrysothraupis Bonaparte 1851 for chrysotis through johannae; and Tangara Brisson 1860 for inornata through seledon. Several of these could be split further, but given that branch lengths are often short and support for many of the nodes is not terribly good, I see little point in doing so at this point. For the present, I prefer to retain a broad Tangara for all as they do form a fairly homogeneous group. b) Ixothraupis Bonaparte 1850: forming a separate clade from the preceding, this genus includes the “spotted” group of 5 species, varia through xanthogastra in the phylogeny; the type species is T. punctata. c) Chalcothraupis Bonaparte 1851: includes only T. ruficervix, for which the genus was described (although there might be some confusion, as Bonaparte apparently also included labradorides here; but according to Hellmayr, ruficervix is the type of the genus.) This species is one of a two-part basal polytomy of the clade that otherwise includes only the “true” Thraupis but it differs considerably in plumage and morphology from these, and is also rather different in plumage and in its fatter bill from the remainder of Tangara. An alternative would be to include it in Thraupis, which I prefer not to do given the above differences. d) Thraupis Boie 1826: the seven species included here (episcopus, sayaca, glaucocolpa, cyanoptera, abbas, ornata (the type) and palmarum) form a coherent group in size and morphology; the species bonariensis and cyanocephala were excluded and will be treated below. e) Euschemon Sclater 1851): includes the remaining 13 species of Tangara, palmeri through cucullata in the phylogeny; the type is flava (now considered a subspecies of cayana). This group includes the most sexually dimorphic members of Tangara as well as several more-or-less “hooded” species. 2) Chlorochrysa and the Paroaria clade: Chlorochrysa forms a well-separated small clade of its own and clearly merits recognition as a separate genus. The Paroaria clade includes a number of small, morphologically distinctive genera showing few resemblances among themselves: Stephanophorus, Diuca, Neothraupis, Lophospingus, Cissopis, and Schistochlamys as well as Paroaria itself. Given the striking degree of divergence among these mostly small genera, I favor maintaining all of them as any lumping would produce virtually undiagnosable salads. The levels of divergence in the phylogeny are high for most as well; the two most closely related, Cissopis and Schistochlamys, are perhaps the mist divergent of the lot. 3) The mountain-tanager clades: this group includes three major clades, each of which includes two or more monophyletic subclades that require evaluation: a) a clade containing two current genera, Wetmorethraupis and Bangsia. The former is sister to the several Bangsia species, which form a monophyletic group. The differences in plumage and size are not that great: Wetmorethraupis looks a bit like a very fancy big Bangsia. However, all species of Bangsia are trans-Andean, with the group centered in the Chocó region, whereas Wetmorethraupis is cis-Andean, occurring to the south of any Bangsia (as well as on the other side of the Andes, which suggests a long-standing divergence). I tentatively favor recognition of both genera. I should also note that this phylogeny provides no support whatever for one of the most frequent lumping in the past, Bangsia into Buthraupis: the two are not even closely related, let alone sisters. b) clade that includes several distinctive, monophyletic groups: i) Thraupis bonariensis and Pipraeidea melanonota: These sister species differ somewhat in size and plumage (the latter suggests a smaller, plainer version of the former), but no more so than do members of several other genera, such that I see no formidable obstacles to including both in Pipraeidea; the alternative would be to name a new, monotypic genus for T. bonariensis (for which no specific previous generic name appears to exist). ii) Iridosornis: the 5 species of this current genus form a monophyletic group for which generic status can be retained. iii) Calochaetes, Delothraupis, and Dubusia: Calochaetes is sister to the other two and differs strikingly in plumage, ecology (basically a foothill to cloudforest species) and somewhat in morphology (more chunky and shorter-tailed) from both of them; I would maintain it as a separate genus. Delothraupis and Dubusia, on the other hand, are similar in morphology and in being high Andean species; they differ mainly in the color of the underparts and somewhat in size. My recommendation would be to lump Delothraupis into Dubusia, as some have done (e.g., Meyer de Schauensee 1970): a number of other genera include species with this degree of differences, and it seems best to recognize their status as sister species. I also note that “Saltator” rufiventris probably falls in this clade; if so, the alternatives would presumably be to include it in Pipraeidea or name a new genus for it, but its generic status can only be resolved by further studies. iv) The Anisognathus clade: this clade includes a basal polytomy of four groups: (A) Thraupis cyanocephala; (B) Buthraupis wetmorei; (C) Anisognathus somptuosus and notabilis; and (D) A. igniventris, lachrymosus, and melanogenys. Here, two options are available: lump all species into Anisognathus Reichenbach 1850, the oldest name for the entire group; or recognize each group as a separate genus. More work will be required to define the structure of this clade, and if all these are lumped the result would be a very heterogeneous group in size, plumage color, and at least bill morphology; hence, I propose the second alternative of four genera, each of which is well characterized. These would be: A) Sporathraupis Bonaparte 1850 for T. cyanocephala; the genus name was coined for this species, which certainly has no place in Thraupis; B) Tephrophilus Moore 1934 for B. wetmorei; again, coined for this species and so used by many authors; C) Compsocoma Cabanis 1851 for A. somptuosus and notabilis, as used by Hellmayr and many others; and D) Anisognathus Reichenbach 1850 for A. igniventris, lachrymosus and melanogenys. Each of these groups is distinctive and easily diagnosed; Hellmayr used the same division of Anisognathus (although he used Poecilothraupis, a synonym of Anisognathus, for group D. Although further research may well reveal more structure in this clade leading to lumping of some of these groups, for the present I think it is best to be consistent with the evidence in hand and, given the clear phenotypic differences among them, recognize all four as genera. v) The Buthraupis clade: this clade breaks basally into two groups: B. montana on the one hand, and Chlorornis and B. eximia and aureodorsalis on the other, C. riefferii being sister to B. eximia and aureodorsalis. One could justify one, two or three genera here, the oddball being C. riefferii, whose bright green plumage and red bill contrast strikingly with the blue-black-yellow plumages of the others. All are moderately to very large, heavy-bodied, rather short-billed high Andean forest tanagers such that if one were willing to overlook the jarring color clash, one could include all in Buthraupis Cabanis 1851. Recognizing two genera would separate B. montana and restrict the color clash to Chlorornis Reichenbach 1850, which would now include eximia and aureodorsalis as well as riefferii. The three-genus alternative would separate eximia and aureodorsalis from riefferii in the genus Cnemothraupis Penard 1919 (type eximia). My inclination would be to recognize three genera, to retain relatively similar branch lengths for all, but given the sometimes rather low support values of several nodes, one could perhaps justify including all in Buthraupis. In summary, this proposal breaks into several subproposals:
Perhaps fortunately, this set of proposals, as it stands, would not require erecting any new generic names, although a number of older generic names would now be resurrected; any further splitting (as in the still-broad Tangara) would require naming at least one new genus. I have not presented separate proposals in which the phylogeny is concordant with the current classification, as in the recognition of Chlorochrysa and Calochaetes; I assume that these would be noncontroversial. I also did not treat specifically the case of “Saltator” rufiventris, which current evidence indicates is a tanager, probably related to Pipraeidea. This will merit a separate proposal when more evidence accrues. To summarize, I recommend YES votes on all eight subproposals. Literature Cited Burns & Naoki 2004 (see proposal 291) Hellmayr 1936: Catalogue of Birds of the Americas, Part 9. Ridgway 1902: Birds of North and Middle America, part 2. SEDANO, R. E., AND K. J. BURNS. 2010. Are the Northern Andes a species pump for Neotropical birds? Phylogenetics and biogeography of a clade of Neotropical tanagers (Aves: Thraupini). Journal of Biogeography 37: 325–343.
1) keep things as simple as possible and make as few changes to the taxonomy (i.e., avoid proposing new generic names or resurrecting old ones that would be unfamiliar). 2) keep the taxonomy consistent with strongly supported nodes in the tree (i.e., no paraphyletic genera and no genera that might easily be rendered polyphyletic with additional data). 3) avoid naming new monotypic genera. Monotypic genera don't tell you anything about relationships to other taxa. All you learn from having a monotypic genus is that whoever recognizes the genus thinks that particular species is morphologically divergent from everything else. To me, this is often a subjective call and that is why I prefer classifications that recognize cladogenesis (nodes) over anagenesis (apomorphies along a branch that aren't shared). We basically only recommended taxonomic changes when the structure of the tree required us to do so. Our recommendations for taxonomic changes in the group are pretty well spelled out in our paper. Rather than repeat them all here, I would ask that the committee see the discussion in our paper, in particular page 336. Below I will give my opinion on each of the proposals A. Divide the Tangara group of Sedano & Burns into five genera, as proposed above: Tangara, Ixothraupis, Chalcothraupis, Thraupis and Euschemon. I recommend a YES. A NO vote would be for maintaining all of these (including Thraupis) in a very broad Tangara (as recommended by Sedano & Burns). I would vote "no" to this proposal. I think the suggested change represents a pretty radical departure. The name Tangara is an incredibly useful and a familiar word to many Neotropical ornithologists and birders in general. If this taxon were to be split up into all these subparts, we would loose the ability to conveniently talk about this taxon as a group. Yes, the Thraupis that are embedded within Tangara are different from the other members of Tangara, but not so different as to warrant sacrificing Tangara itself. In addition, I am very concerned about Euschemon (the genus proposed for palmeri through cucullata). The support for this node is only 0.85 Bayesian posterior probability and 51% bootstrap (basically no support). Further analyses and additional data could easily render this group paraphyletic. B. Maintain a moderately broad genus Tangara, but as restricted above. I tentatively recommend a YES. A NO vote would favor subdividing the restricted Tangara further; the five-way split I suggested above would seem the most reasonable alternative but others are possible, such that a new proposal would be required specifying two or more alternatives. I don't think Tangara should be subdivided for the reasons outlined above. C. Recognize the genera Stephanophorus, Diuca, Neothraupis, Lophospingus, Cissopis and Schistochlamys and Paroaria. While this might seem like oversplitting, most of the nodes dividing this group are fairly basal and all are very distinctive morphologically. I recommend YES; a NO vote would favor lumping of some of them, presumably starting with Schistochlamys and Cissopis (and if the NO wins, a set of new proposals would be needed to determine which and how many lumpings we favor). I agree with this proposal. This is basically sticking with the status quo for these genera and our phylogeny is consistent with all of these genera. For that reason, we did not recommend any changes to classification within this clade. D. Continue to recognize Wetmorethraupis and Bangsia as separate genera (YES) vs. lumping Wetmorethraupis into Bangsia (NO). I agree with this proposal. Bangsia is monophyletic, and thus we see no reason to change the existing taxonomy here. The remaining proposals, E - H, relate to the clade containing Pipraeidea to Buthraupis eximia (Fig. 2). In our paper, we recommended that all of these be placed in a single genus, Iridosornis (which is the earliest name). One reason we did this was that species in Buthraupis and Thraupis were spread across the group, and we wanted to avoid using a bunch of new or resurrected generic names. Plus, using a single genus name for all these species provides an opportunity to highlight their shared distributions (mostly Andean) and evolutionary history. I think having a single scientific name would facilitate and promote their study as a single group of "mountain-tanagers". For the reasons outlined in the paragraph above, I would prefer the committee vote no to proposals E-H and instead merge all these species into Iridosornis. That said, I realize this opinion might not be popular with the committee, so I did think hard about each of these individual proposals. I do think Gary's proposals for this clade offer a way to add only a few names, while retaining many of the traditional genera. For that reason, I might be ok with E, F, some parts of G, and H. For proposal G, I do not think there is enough evidence to split Anisognathus at this point. As we mention in our paper, although we don't have evidence for a monophyletic Anisognathus, we also don't have evidence against a monophyletic Anisognathus. The two clades of Anisognathus may very well connect together with additional data, so it's probably better to stick with the status quo at this point. I would be ok with other aspects of G (Sporathraupis and Tephrophilus). To summarize, for the clade containing Pipraeidea to Buthraupis eximia, I would prefer a single genus Iridosornis, but if the committee is really opposed to this, I would be ok with partitioning these species into these genera: Pipraeidea Iridosornis Calochaetes Dubusia Tephrophilus Sporathraupis Anisognathus Buthraupis Chlorornis Cnemothraupis Regarding Saltator rufiventris, we didn't include it in Sedano and Burns, but this species is sister to Delothraupis/Dubusia when included in an analysis with all the core tanagers. So, the committee could safely merge Saltator rufiventris into Dubusia at this point. Again, thanks for the opportunity to comment. I will be very interested to see how the committee votes on this proposal. What we found in this group is pretty representative of tanagers as a whole (i.e., very few traditional genera that are monophyletic). Comments from Thomas Donegan: “This is a comment on the treatment for the Anisognathus group (part of Proposal G). In Donegan & Avendaño (2010) we looked into the Compsocoma / Anisognathus issue in some detail, but regrettably various paragraphs ended up being excised from the manuscript following peer reviewer comments concerning the scope of the paper. “As things currently stand, Poecilothraupis looks more likely to be the senior name for this group than Anisognathus. Three names (Compsocoma, Anisognathus, and Poecilothraupis) were all described within a maximum period of 2 years. It would seem that the name Anisognathus was first published only on the text below a plate, on a date before the date on which Compsocoma and Poecilothraupis were published. However, the text describing the genus Anisognathus came out after Compsocoma and Poecilothraupis were published. The date of publication of each of these names is in any event very difficult to pin down. One suspects that a messy Commission case may be needed to sort this out, e.g. by fixing dates or suppressing Poecilothraupis and/or Compsocoma. A discussion on the priority of genus names for this group is included in a separate document, in case this is of interest to committee members or others who want to pursue this matter further. “Whatever one’s interpretation of the molecular data, the genus Compsocoma is well-defined morphologically and behaviourally. We noted in Donegan & Avendaño (2010) that: “Blue-winged Mountain Tanager A. somptuosus and Black-chinned Mountain Tanager A. notabilis are more robust birds with stronger flight … but were lumped (with little justification) into Anisognathus by Meyer de Schauensee (1966). We treat Compsocoma as a subgenus of Anisognathus herein.” Where the two genera occur together, Compsocoma is often in higher forest strata than Anisognathus and is more mobile. Several taxa within both a narrow Compsocoma and Anisognathus may require species rank and some of them have been split by modern authors (e.g. C. somptuosus), so the genera produced will probably not be as small long-term as one might initially think. If one were to ignore history and act only rationally, then recognition of Compsocoma would be sensible based on comparative morphological differences between other tanager genera and now poor support for a monophyletic Anisognathus. However, having seen what happened to Pipromorpha, I appreciate that historical treatments are considered important by many persons. “On balance, I like the idea of recognising Compsocoma. However, the main point of this comment is this: moving a whole load of additional species into Anisognathus (as possible under Proposal G but not recommended by either Gary or Kevin) makes for a potentially unstable and unwelcome scenario. If unifying these species were to be thought sensible as a concept (thankfully, it would seem not), it might be worth waiting to sort out name priority issues first. “Reference: Donegan, T.M. & Avendaño, J.E. 2010. A new subspecies of mountain tanager in the Anisognathus lacrymosus complex from the Yariguíes Mountains of Colombia. Bull BOC 130(1): 13-32. Comments solicited from Raul Sedano: “Thanks to Gary for bringing an interesting proposal and the opportunity to provide comments on it. Overall, I do not agree with most the recommendations; however, I find many of them practical to implement. Kevin covered many notions from the paper but I also would like to add few observations from P#437 and the emphasis that the sequence from Sedano and Burns might imply for this group. “Stiles' Proposal (P#437) for delimiting Core Tanagers in roughly 23 to 27 genera is substantially different from the 11 genera proposed as modification of current sequence in Sedano and Burns (2010). They are also different in the level at which subclades are designated as genera. This conflicting taxonomic view between P#437 and Sedano & Burns (2010) could imply that genera designation in this case will easily end up being a matter of taste and consistency (for example see the interesting discussion in P#417). “To add on Kevin's comments on P#437, in our paper, subclade designation for few genera also emphasized the homoplastic nature of external phenotypes in the core tanager radiation. One example of this emphasis is the notion of a species rich genus "Iridosornis" with remarkable species variation in i.e. color and body size. This clade "Iridosornis" could also highlight a shared distributional pattern largely in the Andes that resulted from evolutionary processes in and out of the Northern Andes or likely due to restricted gene flow along the Andes itself. Thus, Iridosornis somehow reflects patterns that are the result of long-term evolutionary processes. Designating this as a genus would have the potential of being also an informative key name as the well-played role of the genus name Tangara, for communication among ornithologist and birdwatchers' communities. “In contrast, Gary's proposal P#437 urges for more fine subclade recognition, emphasizing an eclectic collection of anagenetic diagnostics and with no emphasis whatsoever in share evolutionary patterns among the resulting multiple genera. “Thus, I rather fewer genera as in Sedano & Burns that coincide with the following three overall diagnostic themes on the evolutionary patterns: “1. We learned something about the broad relationships of nine monotypic genera and we were able to reduce that taxonomical uncertainty in some extend to four monotypic genera. Sure, far from perfect solution but P#437 will end up with a taxonomical sequence with 7 monotypic genera (some of them resuscitated names) and nothing about their broad phylogenetics is told with that genera sequence. “2. Taxa whose cladogenesis is concentrated early in their histories partition more of their morphological disparity among, rather than within subclades. Thus, the suggested sequence in our paper reflects this expected pattern. In fact, Tangara and Iridosornis are quite different form each other as you might think for each of the five monotypic genera and Paroaria, Chlorochrysa, Lophospingus and Schistochlamys (This is a generalization under current research). Here, I disagree with P#437 because it may be overemphasizing among subclades differences based on a disparate collection of traits. “3. The larger two genera (Tangara and Iridosornis) somewhat hold a geographical context among clades and their distinctive evolutionary patterns, in and out of the Andes as a whole. (Iridosornis would show a more restricted pattern to the Andes than Tangara or than any other genera in the core tanager clade) “That said, this is my opinion on proposal A-H in P#437. “Subproposal 437 A: I would vote "no", I agree with Kevin comments “Subproposal 437 B: I do not think Tangara should be subdivided BUT if P437 ends up subdividing its sister clade then why not to subdivide Tangara as well. “Subproposal 437 C: I would vote "no" (waiting for the new set of proposals) “Subproposal 437 D: I would vote “yes.” “Subproposal 437 E.: Lump Thraupis bonariensis into Pipraeidea ; I recommend YES (a NO vote would require devising a new genus for the former). For the moment, I leave open the question of "Saltator" rufiventris for want of sufficient data. “Subproposal 437 F: Lump Delothraupis into Dubusia. I recommend a YES; a NO would be for maintaining them as separate, monotypic genera. “Subproposal 437 G: I agree with K. Burns comments on this subproposal. To summarize, for the clade with origin on the most recent common ancestor between Pipraeidea to Buthraupis eximia, I would rather a single genus Iridosornis, but if the committee is really opposed to this, I would be ok with partitioning these species into these genera: Pipraeidea Iridosornis Calochaetes Dubusia Tephrophilus Sporathraupis Anisognathus Buthraupis Chloronis Cnemothraupis “Thank you all for the opportunity of commenting in this taxonomical sequence.” Comments from Robbins: “I presume we are voting on each subproposal. In general, I support Kevin Burns and Raul Sedano’s guidelines for their proposed taxonomic changes. Hence, I vote as follows:
h. “Yes”. Yüklə 84 Kb. Dostları ilə paylaş:
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