Proposal (751) to South American Classification Committee

 

Revise species limits in Polioptila guianensis complex

 

Background

 

         There are five diagnosable forms within the Polioptila guianensis complex: the nominate guianensis [the Guianas south to the Amazon at Manaus], facilis [both banks of the upper río Negro], paraensis [south of the Amazon and east of the Madeira], attenboroughi [south of the Amazon and west of the Madeira], and clementsi [lower Nanay basin near Iquitos, Peru]. SACC currently recognizes two species: guianensis and clementsi.  Morphology and voice suggest that attenboroughi is closest to paraensis (Whittaker et al 2013), and the names facilis and paraensis are both older than clementsi.  Thus, it is safe to assume that the current SACC treatment views all taxa except clementsi as subspecies of guianensis sensu lato.  This general treatment is the outcome of proposals 203 & 204, which provide a good summary of the situation based on Whitney and Alvarez (2005).

 

         More recently, Whittaker et al (2013) presented new vocal analyses and genetic sequence data for guianensis and paraensis alongside their description of attenboroughi.  Based on limited genetic sequence data (1041 bp of ND2, from 4, 1, and 2 individuals of guianensis, paraensis, and attenboroughi, respectively), the closely related paraensis and attenboroughi are somewhat distant from guianensis.  Despite caveats related to the limited sample sizes divergence between (paraensis+attenboroughi) and guianensis appears to be larger than some other sister species pairs in the genus Polioptila, and there is a suggestion that P. guianensis sensu lato is not monophyletic. The vocal analyses show that attenboroughi is diagnosably distinct from other members of the complex (see proposal 619).

 

         A less-discussed feature of Whittaker et al (2013) is their figure 2G, which shows a “multi-note call” from P. guianensis guianensis that

1)   differs from the loudsong shown in Whitney & Alvarez, but

2)   still generally resembles loudsongs within the complex.

 

         Thus, Whittaker et al.’s interpretation that this vocalization is not a loudsong is critical to the notion that there are any diagnostic loudsong characters among this group whatsoever.  For unclear reasons, this recording is not available in the supporting online material at www.hbw.com/supporting-information#polioptila-attenboroughi

 

         Proposal 619 provides a reasonable overview of the current situation.  Some committee members expressed interest in an expanded version of proposal 619 that explicitly gives the committee the option to split facilis and paraensis from the nominate guianensis.

 

New information

 

         There is none.  However, BirdLife/HBW has recently lumped clementsi with guianensis, which casts uncertainty over conservation efforts (including recent endangered species legislation in Peru) directed at the critically endangered clementsi. I do not advocate allowing conservation-related concerns to influence taxonomic decisions.  However, the situation creates heightened applied interest in a formal decision by SACC to lump or continue to recognize clementsi (one way or the other).

 

The present proposal differs from proposal 619 in that it provides separate opportunities to consider the specific status of attenboroughi, paraensis, and facilis. It also asks SACC to reaffirm or reject species status for clementsi.

 

Sub-proposal A:

Split Polioptila paraensis from P. guianensis.

 

Sub-proposal B:

Recognize Polioptila facilis at the species level (distinct from both P. guianensis guianensis and P. (guianensis) paraensis). 

 

Sub-proposal C:

Cease to recognize Polioptila clementsi as a species-level taxon.

 

Sub-proposal D:

Recognize Polioptila attenboroughi as a species-level taxon. 

 

Note:

 

--If A passes, a NO vote on B would be agnostic about which form facilis belongs with. Because paraensis and guianensis both have priority over facilis, this is not destabilizing.

 

--Likewise, if A or B passes, a yes vote on C would be agnostic about which form clementsi should be lumped with.  This poses no nomenclatural issues, as the other names have priority over clementsi.  (This would otherwise be a nontrivial issue; witness the population of Platyrinchus saturatus that occurs sympatrically on white sands with Polioptila clementsi. It is vocally allied to birds from south of the Amazon, not birds from the Guianas!)

 

--Finally, if A or B passes, or C does not pass, a NO vote on D would be agnostic about which form attenboroughi should be lumped with (presumably paraensis).

 

 Recommendations:

 

A: YES.

B: no recommendation

C: NO

D: no recommendation

 

Explanation of recommendations:

 

A:  Data (limited by low sample sizes) suggest that (paraensis+attenboroughi) is not particularly close to nominate guianensis. In fact, (paraensis+attenboroughi) is apparently closer to schistaceigula than to guianensis. At present, the data are highly suggestive and sufficient to tip the scales to a YES vote, in my opinion.

 

B: If A does not pass, then neither should B (the arguments against passage are the same, and the arguments for passage are weaker due to the lack of genetic data). But I think A should pass. In that case, we have little data to determine whether facilis is closer to guianensis or paraensis, or whether it is conspecific with either taxon. As explained in the note above, it would not be destabilizing to hold off on making a decision about facilis.  In that respect, it is fortunate that we have genetic data from paraensis and not facilis, rather than the other way around.

 

C:  If A passes (as I think it should), then I recommend that clementsi should be maintained as a distinct species.  To my ear, the song of clementsi is the most distinctive in the complex (provided that the “multi-note call” of Whittaker et al.’s Figure 2G is not homologous to the loudsong of clementsi). The tiny range and absurd degree of apparent habitat specialization despite extensive poor-soil habitats contiguous with the known range (observations of myself, Pepe Alvarez, Juan Diaz, and Percy Saboya) are unique within the complex. If paraensis is specifically distinct from the nominate, why not clementsi too?

         If A does not pass, then I am agnostic about C. The information presented in Whitney and Alvarez (2005) was enough to convince the committee in proposal 203, and I don’t think subsequent information has changed anything.

 

D:  As the committee recently expressed in comments on proposal 619, this is a difficult case without firm grounds for deciding. Some committee members suggested that they might vote to recognize attenboroughi in the context of a proposal that also allows for the splitting of paraensis from the nominate. So here’s the proposal.

 

 

Jacob Socolar, April 2017

 

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