Proposal (816) to South American Classification Committee

Generic placement and English names of Leptasthenura yanacensis and Sylviorthorhynchus desmursii

PART A. Generic placement of Leptasthenura yanacensis

Background

The Des Murs's Wiretail S. desmursii is a highly distinctive and almost iconic furnariid, largely restricted to Chusquea bamboo stands in the Patagonian Andes. It has just six rectrices, which form a unique slightly incurved lyre shape; in fresh plumage the tail tips are more bulbous and blunt in appearance and when worn the tail comprises just filamentous rachides.

The Tawny Tit-Spinetail L. yanacensis is an even more habitat-specialized furnariid being restricted to high altitude stands of Polylepis woodland and adjacent shrubbery in C Peru, Bolivia, and NW Argentina; it is very locally distributed. It's tail resembles that of many Leptasthenura, although with somewhat longer projecting spines and only ten rectrices, somewhat similar in shape to L. setaria. The bill of yanacensis is longer and finer than other Leptasthenura and resembles that of Sylviorthorhynchus. Leptasthenura yanacensis also shares a rufous forehead, which is not found in other Leptasthenura, with Sylviorthorhynchus.

The vocalizations of Sylviorthorhynchus and L. yanacensis differ strongly from those Leptasthenura in general. The repetitive vocalizations of these two species are lower pitched and slower than the high-pitched and fast trills of Leptasthenura.

As for nest structure, L. yanacensis builds a woven grass dome-shaped nest (pers. obs.) on a horizontal Polylepis bough, whereas S. desmursii builds a globular grass nest. Neither is like many of the cup-shaped, twig nests of Leptasthenura, which are often placed in nests of other birds or in cavities (Remsen 2003).

Current SACC note states:

“22c. Remsen (2003) noted that similarities in general morphology and tail structure suggested a possible relationship of Sylviorthorhynchus to Schizoeaca. However, genetic data (Gonzalez and Wink 2008, Moyle et al. 2009) indicate a close relationship to Leptasthenura, and Derryberry et al. (2011) found that Sylviorthorhynchus was the sister to L. yanacensis. Dickinson & Christidis (2014) transferred yanacensis to Sylviorthorhynchus.”

New data

Leptasthenura yanacensis has been shown to be sister to S. desmursii, and their divergence is as deep as that within Premnoplex (ca. 10MY; Derryberry et al. 2011, see Figure S1-H copied below); desmursii + yanacensis are sister to “true” Leptasthenura, from which they split ca. 15 MYA. In the event of a merger, Sylviorthorhynchus Gay 1845 has priority over Leptasthenura Reichenbach 1853 (type species L. aegithaloides).

This leaves three options for a rearrangement by SACC:

A1) Include only yanacensis and desmursii in Sylviorthorhynchus

A2) Place yanacensis in an, as yet, undescribed genus

A3) Place all Leptasthenura (including yanacensis) and S. desmursii in Sylviorthorhynchus

Recommendation:

We recommend voting YES to option A1, because it would create a coherent genus that can be defined by morphological and vocal features, in addition to being of comparable age to other genera such as the morphologically homogeneous Premnoplex in the same clade. This treatment was also applied by Dickinson & Christidis (2014).

We recommend a NO vote to Option A2. No other generic name is available, and so a new genus would have to be described. This seems inappropriate, because there are several morphological features that link this species pair: bill shape/length, rufous forehead, and reduced number of (unusually long) rectrices. Also, the new genus would be younger than other genera in the clade.

We recommend a NO vote to A3. Given branch depth, and their shared features, we believe that subsuming desmursii and yanacensis into the same genus of “true” Leptasthenura adds two odd-balls to an otherwise rather morphologically and vocally homogeneous genus.

PART B. English names of Leptasthenura yanacensis and Sylviorthorhynchus desmursii

Des Murs's Wiretail is such a well-entrenched name that we strongly vindicate no change. The conundrum of calling Tawny Tit-Spinetail something different then becomes difficult because it does not have a "wiretail" and it superficially looks extremely like a tit-spinetail even though the recent research shows that it is not one.

B1. Retain the current names

B2. Use the name Tawny Wiretail for yanacensis

B3. Use the name Des Murs's Tit-Spinetail for desmursii

Recommendation:

We recommend Option B1. Apart from maintaining stability, with the profusion of new genetic information, we anticipate a multitude of look-alike species that won't tick the boxes. This was also the preferred choice of Dickinson & Christidis (2014).

We could also live with B2, if not so accurate, it demonstrates a loose relationship between the two species.

We do not recommend B3 as it does not lend itself to the genetic data and in any case, Des Murs´s Wiretail is entrenched.

Mark Pearman and Nacho Areta, March 2019

Note from Remsen on voting procedure: To maintain our binary Y/N voting system, for Part A, let’s say that a YES vote is for A1, and a NO vote on means a vote for either A2 or A3 (and specific which one). Likewise for Part B, a YES vote means B1, and a NO vote means a vote for either B2 or B3 (and specific which one). As usual, Tom has Mark Robbins’ vote on the English name.

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Comments from Remsen: “A. YES on A1. This is exactly what Santiago and I have proposed in a perhaps moribund manuscript, and it’s what I did in the Howard-Moore list when I was still part of that project (and which was followed in the final version). A change is required by the genetic data, and we also favored the solution proposed here by Mark and Nacho. B. YES on B1; again, that’s what I in the Howard-Moore list when I was still part of that project (and which was followed in the final version) for the same reasons outlined herein.”

Comments from Claramunt: “A. YES to include only yanacensis and desmursii in Sylviorthorhynchus. The similarities between yanacensis and desmursii (aside from the tail) are striking; setting them apart from Leptasthenura makes this genus more cohesive. Merging all into a big genus Sylviorthorhynchus will not only upset stability but also create an unnecessarily heterogeneous genus.”

Comments from Zimmer:

“A1. YES, for all of the reasons nicely laid out by Mark and Nacho in the proposal.

A2. NO

A3. NO

B1. YES to retaining the current names, but, with one caveat/question. How does retaining “Tawny Tit-Spinetail” for yanacensis impact the group name of “Tit-Spinetail” as it pertains to all “true” Leptasthenura? Following our English naming conventions, aren’t we obliged to remove the hyphen from the group name?

B2. NO

B3. NO.”

Comments from Stiles: “A. YES to include yanacensis in Sylviorthorhynchus; B. YES to maintain current E-names.”

Comments from Pacheco: “YES to A1, for the convincing reasons presented here. NO to A2 and A3.”

Comments from Jaramillo: “Patagonian Andes? The wiretail is neither particularly Patagonian nor restricted to the Andes in my opinion. They are common to the coast! But that is beside the point.

“A1) and A3) NO

“A2) YES – Genera are subjective in how broad a group one chooses to include in a Genus. But they are also meant to be informative in identifying similar groups, and also identifying unique groups or species. If there was ever a unique bird, it is the Des Mur’s Wiretail!! I see no compelling reason to put it with (L.) yanacensis, and think the genus is much more informative if it is kept as a single species genus. Now, that means creating a new genus for yanacensis, and that is ok with me, it is also a pretty different critter. I don’t doubt that they are each other’s closest relatives. Trying to make general match up in ages of divergence to other genera (equivalent ages of lineages) has a general mathematical appeal, but the purpose of the genus is also to describe uniqueness and be informative in a more subjective manner. I think keeping Sylviorthorhynchus as a single species genus is warranted.

“B1) YES – retain current names. We have various lineages called canasteros, or spinetails, or woodcreeper, so I do not mind keeping Tawny Tit-Spinetail.