Proposal (815) to South American Classification Committee
Generic placement and common names of Cranioleuca sulphurifera and Limnoctites rectirostris
PART A. Generic placement of Cranioleuca sulphurifera
The Sulphur-throated Spinetail Cranioleuca sulphurifera was found to be sister to the Straight-billed Reedhaunter Limnoctites rectirostris (Derryberry et al 2011, see Figure S1-B copied below), and this duo was found to be sister to most Cranioleuca (except gutturata) and Thripophaga berlepschi. To avoid a paraphyletic Cranioleuca, the SACC would have to either:
1) Include sulphurifera in Limnoctites
2) Place sulphurifera and L. rectirostris in Cranioleuca
3) Place sulphurifera in an as yet undescribed genus
Behaviorally, both species, C. sulphurifera and L. rectirostris, stand apart from traditional Cranioleuca (type species Cranioleuca albiceps) in their reclusive skulking nature. They are also unique in that both seem specialized on the marsh habitats: L. rectirostris is almost absolutely restricted to sawgrass stands of large-leaved Eryngium, and C. sulphurifera inhabits reedbeds (notably those of Scirpus giganteus). They are largely non arboreal, unlike other Cranioleuca. The juveniles of both species are ventrally buff, unlike other Cranioleuca. Vocalizations are long trills (as in many furnariids), and both songs accelerate towards the end. Whereas the song of L. rectirostris is a high-pitched series of accelerating notes, that of C. sulphurifera is a three-parted lower-frequency trill with an accelerating rising introduction, a flat series of couplet-like notes and a descending accelerating end.
We recommend voting YES to option 1. Ecologically, and morphologically Limnoctites forms a cohesive group, and separating Limnoctites from Cranioleuca also helps the latter gain coherence. The age of this expanded Limnoctites (ca. 2MY) is about the same as the age of Xenerpestes, and it branches off the main Cranioleuca clade at a slightly earlier age than the clade containing Roraimia adusta, “Cranioleuca” gutturata, and Thripophaga cherriei and T. fusciceps.
We recommend a NO vote to Option 2. This would result in an expanded, more heterogenous Cranioleuca, and would represent the second-best option. However, this alternative also creates a behaviorally, ecologically and vocally more diverse Cranioleuca.
We recommend a NO vote to Option 3. No other generic name seems to be available for sulphurifera, and a new genus would have to be described. This seems unlikely to happen, and 1) the divergence time between sulphurifera and rectirostris is well below currently recognized genera in Furnariidae, and 2) the similarities discussed above outweigh their recognition in separate genera.
PART B. English names of Cranioleuca sulphurifera and Limnoctites rectirostris
1) If Part A1 passes, use the name Sulphur-bearded or Sulphur-throated Reedhaunter for C. sulphurifera. There are two widespread and competing names in use, Sulphur-throated and Sulphur-bearded. SACC currently uses Sulphur-throated, but Sulphur-bearded is more accurate, since yellow is restricted to a stripe in the center of the throat, making it look like a beard.
Part B1, option 1.1) Use Sulphur-bearded Reedhaunter for C. sulphurifera
Part B1, option 1.2) Sulphur-throated Reedhaunter for C. sulphurifera
2) If Part A2 passes, use the name Straight-billed Spinetail for L. rectirostris.
3) If Part A3 passes, create a new group name for C. sulphurifera.
4) Retain the current names, regardless of any generic switch.
Recommendation: If Part A1 passes, we support Part B1, option 1.1 (Sulphur-bearded Reedhaunter for C. sulphurifera). If Part A2 passes, we recommend Part B4 (retain current names).
Nacho Areta and Mark Pearman, March 2019
Supplementary Figure 1B from Derryberry et al. (2011)
Comments from Claramunt: “A. YES to include sulphurifera in Limnoctites. I am working on a manuscript about the entire group, but this change is straightforward and we cannot wait anymore. The sister relationship between these two is supported by molecular data. Together they are likely sister to Cranioleuca, but support is only moderate, and even if they are sister to Cranioleuca, I think that recognizing them as a separate genus makes sense given their unique habitat and morphological distinctness. I don’t think they form a coherent group morphologically, rectirostris being very distinctive, but Nacho correctly points to some shared similarities.”
Comments from Remsen: “A. YES. As part of the LSU furnariid project, I was already familiar with this issue and had already made the change to the Howard-Moore classification when I was still working on that project, which was maintained in the final version. Our SACC note on this is as follows, and I would have made the proposal except I thought Santiago was working on a paper on this:
“19. Vaurie (1980) and Sibley & Monroe (1990) merged Limnoctites into Limnornis; this was followed by Dickinson (2003), but see Ridgely & Tudor (1994) and Remsen (2003). Olson et al. (2005) have shown that Limnornis and Limnoctites are not particularly closely related, with Limnoctites embedded within Cranioleuca, and with Limnornis closely related to Phleocryptes (see also Irestedt et al. 2006, Moyle et al. 2009). However, taxon-sampling still so incomplete within the genus that although C. sulphurifera and Limnoctites are almost certainly sisters, their inclusion together in Cranioleuca is uncertain. SACC proposal to merge Limnoctites into Cranioleuca did not pass. Broader taxon-sampling (Derryberry et al. 2011) confirmed the sister relationship between Limnoctites and C. sulphurifera, and that this pair is sister to all other Cranioleuca except C. gutturata. SACC proposal needed. <<wait Claramunt paper>>”
“B1.1: YES, for reasons outlined in. the proposal. I think the cost to instability is outweighed by the benefits of (1) matching a genus name to an English name (increasingly difficult to do), and (2) slightly more accurate “bearded” – normally, I object to name “improvement” per se, but as long as we are going to change the name anyway, we might as well employ the slightly better descriptive name.”
Comments from Zimmer:
A. “YES to Option 1: Include sulphurifera in Limnoctites. Vocally, behaviorally, and in their shared restriction to different types of marsh habitats, these two species (now shown by genetic data to have a sister-relationship) form a coherent genus. Moving them into an expanded Cranioleuca, although perhaps defensible on purely genetic grounds, would obscure the sister relationship between sulphurifera and rectirostris, while watering down the cohesion of Cranioleuca. The morphological distinctions between sulphurifera (wing pattern, yellow beard, minimal ventral streaking, short bill) and rectirostris (less distinctive wing pattern, no contrastingly colored “beard”, absence of ventral streaking, extra-long bill) don’t seem worthy of recognition in separate genera, nor does the divergence time between the two support such a conclusion. The biggest single morphological distinction of rectirostris is its “Pinocchio” bill, which is likely a trophic adaptation tied to its specialized relationship with Eryngium, and therefore, a relatively plastic character subject to extreme selective pressure.
B. “YES” to Part B1, option 1.1: use “Sulphur-bearded Reedhaunter” as the English name for sulphurifera. If A1 passes, then the English name of rectirostris would remain the same (“Narrow-billed Reedhaunter”) and the group name of sulphurifera would change from “Spinetail” to “Reedhaunter”, which is even more appropriate for sulphurifera than it is for rectirostris (which doesn’t actually inhabit reeds, but grassy marshes with Eryngium). I think that “Sulphur-bearded” is more accurate and descriptive as a modifier than “Sulphur-throated”, not only because the yellow is confined to a median stripe (as opposed to covering the entire throat), but also, because those yellow feathers appear to me (based strictly upon field observation) to be elongate relative to the other throat feathers, and also expressive. I’ve seen individuals in which the yellow stripe was not apparent one moment, and then extended like a pointy little beard (almost like that of an Oxypogon hummingbird) the next. As an aside, I might also add that the expressive nature of the yellow “beard” in sulphurifera, would, off the top of my head, represent a unique character state if this species were to be retained in Cranioleuca – at least I can’t think of any Cranioleuca with a contrasting throat patch whose visibility is transient/expressive (much as the black throat patches of many Synallaxis spinetails are, and, to a lesser extent, the yellow-chin patch of Certhiaxis).”
Comments from Stiles: “A. YES to include both in Limnoctites (hence NO for alternatives); B. YES for Sulphur-bearded.”
Comments from Pacheco: “YES in option 1, an appropriate solution that fits with behavioral information. I ask for Vitor's confirmation on this particular case. Limnoctites being masculine, the sulphurifera epithet possibly must agree: Limnoctites sulphuriferus.
Comment from Remsen: “Dickinson & Christidis (2014) indicate that Limnoctites is masculine and that sulphurifera is a variable ending; therefore, if the proposal passes, the variable ending must be changed.”
Comments from Jaramillo: “A1 YES – move both to Limnoctites. Similarity is clear when you know these birds in the field, Straight-billed has that massively long bill, but we know how plastic this feature is in birds. 2 and 3 NO.
“B1 – Really there is no need to change the names, and usually I would go for stability over a change. But then again, these are not birds that most English-speakers know well or encounter frequently. As such, an improvement of the name and moving them both to reedhaunters is ok with me. Sulphur-bearded is the best name. Having said that, there is no need to change the name of the Curve-billed Reedhaunter in my opinion, let’s not get in a cascading need to improve every name that is out there. Just like Spinetail applies to a bunch of birds, and Canastero does as well, we can be OK to have Reedhaunter apply to more than one genus right?