Proposal (#365) to South American Classification Committee

 

Proposal to South American Classification Committee

Erect the new genus Eleoscytalopus for the "Scytalopus" indigoticus species group

Effect on SACC list: If it passes, this proposal would lead to the recognition of a new genus of Rhinocryptidae, and would result in moving two species currently included in Scytalopus to this new genus.

Background: Ornithologists have long recognized that the tapaculos in the genus Scytalopus occurring in Eastern Brazil can be clearly separated in two distinct assemblages, the S. speluncae and S. indigoticus species-groups. The distinctiveness of these two groups in plumage characteristics and, particularly, in vocalizations, has even led some authors to suggest they are not each other's closest relatives, and thereby to propose two separate events of colonization of this region from Andean stock. Kevin Zimmer highlighted the distinctiveness of the voices of S. indigoticus and S. psychopompus with respect to all other Brazilian Scytalopus recently in his comments on SACC proposal no. 329.

New information: A recent study by Maurício et al. (2008) has provided strong evidence that the genus Scytalopus as currently defined is not monophyletic. Sequences of two mitochondrial and two nuclear gene fragments independently suggest that the "Scytalopus" indigoticus species group (i.e. S. indigoticus and S. psychopompus) is actually the sister group to the genus Merulaxis, whereas Scytalopus in a strict sense (i.e. a clade that includes Andean taxa including the type species of the genus S. magellanicus and the Brazilian S. speluncae species group) is sister to the genus Eugralla, with Myornis sister to the Eugralla-Scytalopus clade. As surprising as this result might seem, it is strongly supported by all genes, and there are quite a few informative indels in nuclear introns that provide additional support. Moreover, Maurício et al. provided evidence from internal anatomy that this phylogenetic arrangement is consistent with putative skeletal and syringeal synapomorphies, perhaps the most notable of which is the lack of a furcula (i.e. fused clavicles) in Myornis-Eugralla-Scytalopus, and the presence of this structure in Merulaxis and the S. indigoticus group. Based on these results, Maurício et al. (2008) recommended erecting a new genus Eleoscytalopus for S. indigoticus and S. psychopompus. The alternative of transferring these species to Merulaxis was considered less useful as it would lead to a highly heterogeneous genus in comparison to other genera of tapaculos currently recognized by SACC.

Analyses and recommendation: Noting I am a coauthor of the Maurício et al. paper, I highly recommend a YES vote. I would also add that the sister relationship between Merulaxis and Eleoscytalopus is further supported by plumage similarities (i.e. bluish coloration on the upperparts) and arguably by vocalizations (the "froggy trill" of Eleoscytalopus resembles the voice of Merulaxis).

References:

Maurício, G. N., H. Mata, M. R. Bornschein, C. D. Cadena, H. Alvarenga & S. L. Bonatto. 2008. Hidden generic diversity in Neotropical birds: molecular and anatomical data support a new genus for the "Scytalopus" indigoticus species-group (Aves: Rhinocryptidae). Molecular Phylogenetics and Evolution. In press: doi: 10.1016/j.ympev.2008.06.017

Note: Although the paper referenced above has not appeared in print, a corrected proof (which will not be modified further) is available online at the MPE website, and also (at least temporarily) will be available at this site:

http://evolvert.uniandes.edu.co/Site/Publicaciones_files/mpe08-1.pdf

 

C. D. Cadena, August 2008

=================================================================

Comments from Schulenberg: "YES. Count me among those who were surprised by this result. But the new phylogeny, indicating that Scytalopus is polyphyletic if it were to include the indigoticus species group, is very well supported."

Comments from Nores: "YES. Es evidente de que se trata de dos grupos bien diferentes, a pesar del parecido externo. Lo que si, yo no veo que el parentesco entre Eleoscytalopus y Merulaxis se evidencia también por el color, como lo indica Cadena. Para mi son muy distintos tanto en color como en aspecto."

Comments from Jaramillo: "YES - I recall Bennett Hennessey playing some tape of indigoticus to me, a taxon I have no experience with, and was blown away by how different the vocalizations of that creature were. The coloration is actually rather divergent from standard Scytalopus too. So we have that, and the genetic work, which all point to a separate group and one that is allied to the Bristlefronts. In addition to erecting the genus, they should also be placed closer to Merulaxis."

Comments from Remsen: "YES. The genetic data require recognition of this new genus."

Comments from Stiles: "YES. Genetic data are solid and fit with information on vocalizations
and morphology."

Comments from Pacheco: "YES. Os dados apresentados corroboram em demasia a proposição."

Comments from Zimmer: “YES.  I realize that this proposal has already passed, but as my earlier comments on SACC proposal #329 should make clear, the voices of the indigoticus really are very different from those of Scytalopus.  Mauricio et al. 2008 have done an excellent job of justifying the erection of this new genus, and I am in total agreement with their conclusions.”