Proposal (866) to South American Classification Committee

 

Change the scientific name of Chapada Flycatcher (yes, again)

 

Background: Chapada Flycatcher came to our attention when it was described as Suiriri islerorum by Zimmer et al. (2001). As later was documented by Kirwan et al. (2014), however, islerorum is a junior synonym of Elaenea affinis Burmeister 1856. This issue was considered several years ago by SACC (Proposal 671), as a result of which the SACC scientific name for Chapada Flycatcher became Suiriri affinis.

 

Mentioned in passing (page 75) in the 2001 paper was the observation that "preliminary molecular analyses of tissue samples indicates that S. islerorum [= S. affinis] is strongly differentiated genetically from both S. s. affinis [now Suiriri suiriri burmeisteri] and S. s. bahiae (J. Bates pers. comm.). Those results will be presented elsewhere as part of an overview of genetic diversity in Suiriri".

 

New information: Unfortunately Bates never published an overview of genetic diversity in Suiriri. Eventually, however, another research group tackled this issue. Lopes et al. (2018) documented that indeed "Suiriri" affinis and Suiriri suiriri are "strongly differentiated genetically":

 

 

 

 

Their phylogenetic analysis, based on DNA sequence data from mitochondrial and nuclear genes, indicates that Suiriri suiriri is an elaenine flycatcher, consistent with standard classifications (e.g., Traylor 1979, Dickinson and Christidis 2014) and with other recent phylogenies (e.g., Ohlson et al. 2008, Tello et al. 2009), whereas "Suiriri" affinis is deep within the fluvicoline group.

 

In the apparent absence of an available name (and I hope that they did due diligence here), Lopes et al. proposed a new genus, Guyramemua, with Elaenea affinis Burmeister 1856 as the type species.

 

Analysis: Clearly affinis and suiriri are not congeneric.  We have two options. Option One is to transfer to Chapada Flycatcher to Guyramemua, which is a bit of a mouthful, but is an available name.  Guyramemua is neuter, so the spelling of the species name must change from affinis to affine.

 

The second option, as pointed out by Santiago Claramunt, would be to transfer Chapada Flycatcher from Suiriri to Sublegatus. In this case, the spelling of the species epithet would not change.

 

Recommendation: I recommend Option One, to change the scientific name of Chapada Flycatcher from Suiriri affinis to Guyramemua affine.  I recognize the relatively short branch length from Chapada Flycatcher to Sublegatus.  But, as was described in Zimmer et al. (2001), Chapada Flycatcher has a distinctive wing-wagging display that is unusual (although not unique) among tyrannids; placing it in Sublegatus, in which such a display seems to be lacking, serves to downplay one of the more interesting attributes of Chapada Flycatcher.  That said, the most important task here for SACC is simply to get Chapada Flycatcher out of Suiriri, where it does not belong.

 

Literature Cited:

 

Dickinson, E.C., and L. Christidis. 2014. The Howard & Moore complete checklist of the birds of the world. Fourth edition. Volume 2. Aves Press, Eastbourne, United Kingdom.

 

Kirwan, G.M., F.D. Steinheimer, M.A. Raposo, and K.J. Zimmer. 2014. Nomenclatural corrections, neotype designation and new subspecies description in the genus Suiriri (Aves: Passeriformes: Tyrannidae). Zootaxa 3784: 224-240. https://doi.org/10.11646/zootaxa.3784.3.2

 

Lopes, L.E., A.V. Chaves, M.M. de Aquino, L.F. Silveira, and F.R. dos Santos. 2018. The striking polyphyly of Suiriri: convergent evolution and social mimicry in two cryptic Neotropical birds. Journal of Zoological Systematics and Evolutionary Research 56: 270-279. https:/doi.org/10.1111/jzs.12200

 

Ohlson, J.I., J. Fjeldså, and P.G.P. Ericson. 2008. Tyrant flycatchers coming out in the open: phylogeny and ecological radiation of Tyrannidae (Aves, Passeriformes). Zoologica Scripta 37: 315–335. https://doi.org/10.1111/j.1463-6409.2008.00325.x

 

Tello, J.G., R.G. Moyle, D.J. Marchese, and J. Cracraft. 2009. Phylogeny and phylogenetic classification of the tyrant flycatchers, cotingas, manakins, and their allies (Aves: Tyrannides). Cladistics 25: 429-467. https://doi.org/10.1111/j.1096-0031.2009.00254.x

 

Traylor, M.A., Jr. 1979. Family Tyrannidae, tyrant flycatchers. Pages 1-299 in M.A. Traylor, Jr. (editor), Check-list of birds of the world. Volume 8. Museum of Comparative Zoology, Cambridge, Massachusetts.

 

Zimmer, K.J., A. Whittaker, and  D.C. Oren.  2001.  A cryptic new species of flycatcher (Tyrannidae: Suiriri) from the Cerrado region of central South America. Auk 118: 56–78.

 

Tom Schulenberg, July 2020 (with minor subsequent revisions to original proposal’s Analysis and Recommendations sections to address Claramunt et al.’s concerns)

 

 

 

Comments from Remsen:  YES.  I don’t think anyone saw this one coming!  But that’s what the DNA says, and as Tom pointed out, assuming due diligence has been performed on available names, a new genus is required.”

 

Comments from Stiles: “YES.  Required by the genetic data.”

 

Comments from Areta: “YES. Putting affinis in Sublegatus is not a reasonable choice, given the marked differences in displays, behavior and vocal structure.”

 

Comments from Claramunt: “NO.  Very interesting and robust phylogenetic result, and very interesting biological explanation.  However, regarding the taxonomy, the most obvious option should be to transfer the Chapada Flycatcher to Sublegatus, not to create a monotypic genus.  From the evidence presented, it seems to me that affinis fits nicely in Sublegatus, which is an already smallish and homogeneous genus.  This is apparent from the evidence shown in the paper itself, discussing the similarities of affinis and Sublegatus, note the stubby beak typical of Sublegatus (see the photographs in Fig. 1). Of course affinis is not identical to the other Sublegatus -- it’s a different species, somewhat modified by social mimicry -- but I think it fits in Sublegatus nicely. Branch lengths seem within the range of other genera. In sum, I think the cons outweigh the pros; I don’t see the need to create a monotypic genus and introduce a new (and difficult to pronounce) name in the already complex taxonomy of the Tyrannidae.”

 

Comments from Robbins: “NO.  Clearly affinis needs a new generic allocation; however, I vote No, for the sole reason of having to create yet another monotypic genus.  As Santiago suggested, I support transferring affinis to Sublegatus.  If we can place credence in comparative node depth and genetic divergence, putting affinis in Sublegatus would be on par with how Myiophobus is defined (see figure in the proposal from Lopes et al.).”

 

Additional comments from Remsen: Given Santiago’s comments and Mark’s comment on node depth, I withdraw my Yes vote until better justification for the new genus is presented.

 

Comments from Stiles: “NO. Yes to separating affinis from Suiriri; but I agree with Santiago that the genetic evidence is also compatible with including it in Sublegatus.”

 

Comments from Bonaccorso: “NO. Completely agree with Santiago and Mark. No need for another monotypic genus within Tyrannidae, as affinis can fit nicely within Sublegatus.”

 

Comments from Zimmer: “YES.  It has been clear to me, ever since John Bates did the original molecular analysis on the 10 specimens of Suiriri "islerorum" (= affinis) and the 10 specimens of S. s. affinis (= burmeisteri) that we collected from the Chapada dos Guimarães region of Mato Grosso, Brazil, that "islerorum" (= affinis) would require a new generic allocation.  When John called to give me the results, his response to my question of "Well, does your analysis support our contention that there are two species [of Suiriri] involved?", was to say, ‘Not only are there 2 species, but they don't even belong in the same genus!’.  Off the top of my head, I believe he found 16% sequence divergence between "islerorum" (= affinis) and "affinis" (= burmeisteri), and the closest thing he could find to "islerorum" was Sublegatus (8% sequence divergence).  So, before even publishing our results describing "islerorum" (= affinis) as a species distinct from the rest of Suiriri, we knew that it would need to be reallocated to another genus.  That we did not do so at the time, was due partly to the desire to prioritize the findings regarding species-limits, and partly because the genetic work underpinning the need for generic reallocation was part of a much larger genetic study that John and his colleagues were working on.  So, yes, the need for generic reallocation of Suiriri affinis is clear.

 

“I disagree with Santiago's contention that the "most obvious option should be to transfer the Chapada Flycatcher to Sublegatus, not to create a monotypic genus."  In my opinion, It does not "fit nicely in Sublegatus", which, as Santiago notes, is "an already smallish and homogeneous genus."  Aside from the general plumage pattern of grayish chest, yellowish belly, brownish-olive upperparts, and buffy wingbars (a general pattern not unique by any means to Sublegatus, and, in fact, shared with Elaenia, Myiarchus, Suiriri, and gobs of tyrannulets spread through various genera), the only morphological character that I can see that could be considered as uniting S. affinis with Sublegatus is the stubby bill (mentioned by Santiago).  I think it's fairly well established that bill morphology is a very plastic character, subject to extreme selective pressure, and should not be given undue weight as a taxonomic character.  Sticking with plumage characters, there is not one described taxon in Sublegatus that has either the boldly contrasting pale rump, the very blackish tail, or the broad, contrasting, buffy terminal band to the tip of the tail, let alone the entire suite of these plumage characters that distinguish the Chapada Flycatcher.  More importantly, the vocal repertoire of Chapada Flycatcher is off-the-charts different from that of any of the named species of Sublegatus (all of which, are fairly similar to one another, particularly arenarum and modestus), and the habitual duetting behavior of Chapada Flycatcher, accompanied as it is by exaggerated physical displays, themselves stereotypical both to species and sex, is something that is not even approached by anything that I've seen any Sublegatus do.  As for the question of comparative node depth and genetic divergence as seen in Lopes et al. (2018), it also looks as if the branch lengths between affinis and Sublegatus are not that different from those between Alectrurus and Gubernetes, and the node depth of affinis + Sublegatus would be comparable to that of Empidonomus + Tyrannus, so that does little to budge me off my position that Chapada Flycatcher is a real outlier relative to the small and homogeneous grouping of Sublegatus as currently constituted.

 

“Frankly, I don't see much difference between this case and the one being considered in Proposal #867 (concerning reallocation of "Thraupis/Pipraeidea" bonariensis to its own monotypic genus), which everyone seems to support, other than that adoption of that proposal would leave us with two sister-species, each placed in monotypic genera, whereas, adoption of Proposal #866 would leave us with sister genera, one of which contains 3 morphologically, vocally and behaviorally homogeneous species, and the other of which is monotypic and distinct from its sister genus in plumage, vocalizations, and complex display behaviors.”

 

Comments from Jaramillo: “YES, This is a deep branch, also there are some major differences in voice/behavior between Chapada and Sublegatus. It could be argued that affinis fits nicely in Sublegatus based on structure, but then again it fit nicely in with Suiriri as well! So that is not much of an argument to me. The deep branch and behavioral, vocal differences lead me to vote yes on Guyramemua.”

 

Additional comments from Zimmer: “Interesting to read the latest round of comments regarding whether to recognize a monotypic genus Guyramemua for the reallocation of Suiriri affinis versus moving it to Sublegatus, and, more generally, on the whole question of the desirability of monotypic genera.  There have been lots of points raised by those who favor the reallocation to Sublegatus, and I would like to address some of them, both with respect to the specifics of this Proposal, and from a more generalized, philosophical perspective.  My apologies in advance for the length of my remarks!

 

“Mark states that “Clearly, defining genera is highly subjective, so there is no right or wrong.”  I agree with this statement 100%.  Once the condition of monophyly has been met (as in the present case), whether to recognize one genus or two becomes a matter of taste.  I’ve made no secret of my preference for recognizing genera that are more narrowly defined and internally cohesive (morphologically, vocally and ecologically), but I realize that not everyone shares that preference. Several members have argued against creating monotypic genera, on the grounds that these are, somehow, not informative.  I would counter this by echoing Vitor’s comments on the topic, which, in my opinion, were spot-on.  It all depends on what sort of information one looks to a working classification for.  If all you are interested in is the phylogeny, then go to the phylogeny!  Mark notes that “What I have taken from the past 10-15 years of genetic data sets, which have become the underpinnings of our taxonomy, is that differences in morphology, voice, habitats, etc. are quite limited in defining relationships except in cases of species limits.”  To a certain extent, I agree with this assertion too.  But then, what are we to do with this?  If, as Van suggests, “that a lot of the subjectivity would be removed by focusing more on comparative node depths etc. as a proxy for time” and that such an approach would be better “than the unrepeatable artsy subjectivity we all use in drawing generic boundaries within a monophyletic group”, my question would be “So what kind of additional information, aside from what is already evident in the phylogeny, would we be imparting by drawing generic boundaries based upon comparative node depth?”  Or, as Vitor put it:  “So phylogenetics is more important than the biology of the species?”

“I agree with Van that “each of us has a different idea of the subjective limits of generic boundaries” and that “those ideas often depend on how familiar one is with the group”, but I’m not sure what he was getting at when he added “the greater the familiarity, the greater weight to the differences, generally”.  Was this an expression that more weight should be given to the evaluation of differences by those with greater familiarity, or, was it implying that there was inherent bias towards recognizing differences by those with greater familiarity?  If the latter, I would push back by suggesting that the greater the familiarity one has with all of the taxa involved, the more objectively one can evaluate and contextualize not only the differences between taxa, but also the similarities.  In the case of the Chapada Flycatcher, Van’s observation would seem to ring true, because all of the people weighing in who know both S. affinis and Sublegatus in life seem to recognize just how different they are, and, consequently, favor the Guyramemua option.  However, I would argue that the bias in this scenario lies with those who don’t know Chapada Flycatcher in life, and who, without that experience to draw upon, necessarily, revert to superficial, coarse-grained similarities/differences in plumage, which, as the genetics have shown us over and over again, particularly among suboscine passerines, is much less indicative of relationships than similarities/differences in vocalizations and biology/ecology.

 

“In this context, I would urge everyone to review the positions taken over the recognition of Cyanophonia in Proposal #856.  Some among us expressed the desirability of resurrecting that genus (despite comparatively short node lengths), based on Cyanophonia being “phenotypically and genetically distinct” (from Chlorophonia); that Cyanophonia is “monophyletic, highly supported and clearly diagnosable by plumage”; that such a path would result in a “simple and descriptive classification”; and, that to do otherwise (i.e. transfer the Cyanophonia species into Chlorophonia), would result in a genus (Chlorophonia) that “would no longer be diagnosable.”  Yet, the same members who made these arguments supporting the restoration of Cyanophonia, favor sinking the Chapada Flycatcher into Sublegatus, despite the fact that the Chapada Flycatcher is also “phenotypically and genetically distinct”, “monophyletic”, “highly supported, and clearly diagnosable by plumage”, and, that placing it in its own genus would result in “a simple and descriptive classification”, whereas, reallocating it to Sublegatus would result in a slightly simpler classification but one which, would be, arguably, less descriptive, and which, I would contend, would make Sublegatus so heterogeneous as to render it undiagnosable.  There are only two rationales that I can see for the conflicting approaches taken to these two cases: 1) an underlying, philosophical distaste for monotypic genera; and/or 2) lack of appreciation for just how different affinis is, relative to Sublegatus.  I understand the philosophical differences over monotypic genera (although I would reference Vitor’s defense of monotypic genera, which makes the case better than I could), but, again, some of the same members who are so opposed to erecting a monotypic genus for the Chapada Flycatcher, had no such qualms in recognizing not one, but two monotypic genera, when it came to removing Blue-and-yellow Tanager from Pipraeidea and placing it in Rauenia (a move that I wholeheartedly supported as well).  The primary distinction between these cases (Cyanophonia and Pipraeidea/Rauenia) and Guyramemua that I can see, is that the latter involves a group in which plumage is evolutionarily conservative (rendering differences between taxa subtle), whereas the other two examples both involve groups in which plumage is anything but conservative, and in which plumage differences are blatantly obvious in photographs, even to those unfamiliar with the various taxa in life.

 

“Assuming that we are all in agreement that defining generic boundaries is subjective, and that there is no right or wrong answer, then, it seems to me that Proposal #866 should be structured with 2 distinct parts:  #866A, remove Chapada Flycatcher from Suiriri (which I think, everyone agrees with); and #866B, erect a monotypic genus.  However, I don’t think that this should be structured in a way that moving affinis to Sublegatus becomes the default option if we fail to get the votes needed to pass #866B.  Transfer to Sublegatus should require a separate proposal, requiring the same 2/3s majority vote for passage.  To do otherwise, would result in tipping the scales in a way that gives less weight to the votes of the members who actually know the involved taxa in life.  Nor do I agree, as Santiago seems to suggest in his response to Vitor, that the burden of proof in this debate falls on those who contend that the Chapada Flycatcher is too different to include in Sublegatus.  Starting with Zimmer et al. (2001), there have been some very detailed published accounts detailing not only the morphological characters that diagnose Chapada Flycatcher, but also spectrographic evidence of the calls, songs and duets, as well as detailed behavioral descriptions, including the sexually stereotypic physical displays associated with the duets.  Although the bulk of these discussions were focused on presenting these distinctions relative to Suiriri, I did include a comparative discussion of Sublegatus in my diagnosis of Chapada Flycatcher.  All anyone lacking field experience with Chapada Flycatcher has to do to see for themselves the distinctiveness of this taxon relative to Sublegatus, is to go to the WikiAves on-line photo archive and search “Suiriri affinis” – you will find page after page after page of photos, including gobs of spectacular ones of wildly displaying birds showing off the contrastingly pale yellow rump, the much blacker tail, and the contrasting pale terminal band to the tail, all features lacking in all 3 currently recognized species of Sublegatus, and all features which, not coincidentally I imagine, are prominently featured in the wing-and-tail-flapping displays of Chapada Flycatcher.  Then, while still on WikiAves, use the search bar to go to the pages for the various members of Sublegatus.  The distinctions should be obvious.  Scrub-Flycatchers look like miniature Elaenias to me – the whole jizz is different from Chapada Flycatcher, which, no surprise, gives off a Suiriri-type feel, which helps explain why it was erroneously placed in the incorrect species, genus, and even subfamily for so long, without detection.  Similarly, it is not difficult to go to an on-line sound archive such as Xeno-Canto and compare vocalizations of Chapada Flycatcher to those of the various Sublegatus species.  I guess what I’m saying, is that the “quantitative and comparative evidence” is abundant, published, and out there (in the public sphere), and that the burden to provide it (beyond citation of sources for that evidence) should not be incumbent on either the author of the Proposal (in this case, Tom Schulenberg), or, on those of us supporting the Guyramemua option, at least not any more so than it should be incumbent on members supporting the expanded Sublegatus option to provide evidence supporting their position.  The default position for not being sufficiently familiar with the evidence should be “abstention/recusal” from voting, not a “NO” vote.

 

“Again, the burden of proof should be at least as high for those wanting to sink affinis into Sublegatus.  As Vitor stated:

 

“So, if SACC members do believe Chapada Flycatcher belongs in Sublegatus, I plea all voters do that based on some rationale that justify recognizing all 4 species as a unit, despite the many differences highlighted by Kevin -- and not based on "I don't like monotypic genera".

 

“Many of us, when evaluating species-limits, employ the “yardstick approach” in our decision-making process, using degree of morphological, vocal, behavioral and genetic difference between other recognized species in the same genus to infer the significance of differences in the taxon being evaluated.  It strikes me that this is the same technique that we would be using when focusing on comparative node depths in related groups to delimit genera.  But why not apply the comparative yardstick approach to the whole suite of morphological, vocal, behavioral and genetic data in making decisions about delimiting genera within monophyletic groups?  Node depth, as a proxy for time, is something that can be “seen” by birders or ornithologists only when looking at a tree diagram.  How intuitive, descriptive, or utilitarian is a classification defined by things that can’t be observed on the living bird, particularly when these are in opposition to things such as morphology, voice, and behavior that are obvious to the observer?  Because, there is no right or wrong answer, why not have a taxonomy informed by genetic data, and adhering to principles of monophyly, that reflects what can be observed in the living birds, instead of prioritizing the abstract (node-depth = time)?

 

“I would challenge everyone advocating for placing affinis in Sublegatus to look at the morphological, vocal, behavioral and genetic distinctions between the three species of Sublegatus as currently constituted, and then compare that “yardstick” to the differences between affinis and any of the other three species.  Then, explain to me how you would diagnose the expanded genus of Sublegatus + affinis?  I fully understand that there are all kinds of precedent for incorporating some very different species within the same genus.  Mark invoked the example of the morphological, vocal and ecological diversity encompassed within Setophaga as an example.  But, to my mind, that is a very different case.  Setophaga is a speciose genus encompassing striking diversity in plumage, vocalizations and ecology, whose constituent species were previously spread across four genera.  Even before so many species from those genera were folded into Setophaga, there was a striking amount of within-genus variation – just look at the amount of variation (morphological, vocal, ecological) that was included within Dendroica.  That example is not even remotely similar in my opinion to what we see in the present case, in which you are talking about adding one very different member (an outlier morphologically, vocally, and behaviorally) to a small, internally cohesive, and extremely homogeneous group.

 

“Finally (!!!), I would just reiterate, that since neither approach (monotypic genus for affinis versus expanded Sublegatus) is inherently more correct than the other, and, since, in the present case, there is no real argument to be made one way or the other on grounds of taxonomic stability (i.e. affinis is going to a new genus one way or the other, and, either we end up erecting a new genus, or, we upend how an existing genus is diagnosed), that we should not treat an expanded Sublegatus as the default option to not recognizing Guyramemua, and, instead, treat it as a separate proposal that would require proponents of that treatment to support and defend.  It strikes me as irrational, that, in a case where the status quo (in this case, maintaining affinis within Suiriri) is not a tenable position, and that neither of the two alternatives on the table are inherently right or wrong, that the default position should be that favored by members who have no experience with affinis in life, and who, by their own admission, “have not examined specimens or comparative evidence”, and are “left in darkness”, especially, when the recognition of Guyramemua has the support of all of the committee members and outside advisors who actually know the living bird.”

 

Comments from Whitney: “Van asked that I chime in on the subject of generic alignment in the Sublegatus clade.  First, I completely agree with the sentiments expressed (most elaborately) by Vítor and Kevin.  To summarize:  Generic boundaries within a well-supported, multi-species clade are largely subjective, and, in attempting to draw them as helpfully or informatively as possible, we should look to the biology of the species involved, “the living birds,” as Kevin closed his opinion yesterday.

 

“Although it has not been the subject of concerted phenotypic or genetic study, Sublegatus is clearly a paraphyletic assemblage, and even includes (supposedly named) taxa that breed in sympatry; additional taxa may overlap during austral winter.  I’ll take a shot at four similar-looking, vocally strongly differentiated, BSC species-level taxa throughout the range from e Panama to nc Argentina.  Chapada Flycatcher is clearly different from them all, both morphologically and vocally.  Behaviorally, it is much more similar, however, including the wing/tail display.  The nominate and some other populations of Sublegatus do perform a similar display as members of a pair come together, albeit a “smaller” display — less dramatic and less prolonged — than the display of Chapada Flycatcher — the point being that there is, in fact, a similar behavior there, with no assumption of homology (several flycatchers in at least three subfamilies perform somewhat similar displays!).  Obvious differences in size aside, in the field, I see as many or more similarities than differences between Chapada Flycatcher and the various Sublegatus.  So, on balance, I might lean toward using Sublegatus for them all, to heighten attention to the fact that they are sisters.

 

“But I think there is one over-arching reason not to do that — and that is phylogeography of the clade.  The entire distribution of Chapada Flycatcher is overlapped by sister Sublegatus, and, moreover, the two occur not just in sympatry, but in syntopy across a vast area, which points to significantly more ecological divergence than meets the eye (i.e., there’s a lot to learn about these birds).  Although "sisters in syntopy/sympatry" has not been invoked in making taxonomic judgements, I suspect it is highly informative, as implied in the description of Herpsilochmus sellowi (Whitney et al. 2000), which is widely or locally sympatric with four, syntopic with at least two, Herpsilochmus.  We now know it’s sister to Biatas!

 

“I vote for Guyramemua.”

 

Additional Comments from Bonaccorso: “YES. I change my original vote to accept Guyramemua. The Fluvicolinae are so complex) for so many reasons) that if using Guyramemua helps to understand evolutionary change in the group better, so be it.”

 

Comments from Pacheco: “YES. I vote for Guyramemua. I know directly the species involved in this “philosophical” case. It may not be important, but in the field I never made any association between Chapada Flycatcher and the small homogeneous group of Sublegatus. Display behavior and vocal repertoire are blatantly and distinctly at odds with what you see in Sublegatus. This feeling seems to be very strong in those who know both groups better: Kevin, Bret and Vitor. I agree with them that there is less harm in treating him in a monotypic genus Guyramemua than sinking him in Sublegatus.”