Proposal (806) to South American Classification Committee

 

 

Recognize Elaenia sordida as a separate species from Elaenia obscura

 

Effect on SACC: This proposal would add a species to the list by removing the subspecies sordida from Elaenia obscura and elevating it to species rank.

 

Background: The SACC currently treats Elaenia obscura as a single species with two subspecies, Elaenia obscura obscura and Elaenia obscura sordida. The populations of the two taxa are disjunct: obscura is distributed along the east slope of the Andes from south Ecuador to Bolivia and northwest Argentina; sordida occurs in south central and southeast Brazil, east Paraguay, northeast Argentina and extreme northern Uruguay.

 

Analysis: Hosner (2004) stated that sordida is on average larger than obscura and described some differences in plumage but there is no suggestion that these are sufficient to justify status as a distinct species.

 

Rheindt et al. (2008), however, stated that ‘the mitochondrial divergences between Andean E. o. obscura and Atlantic E. o. sordida are comparable to those between sister species of Elaenia (e.g. E. spectabilis and E. pelzelni), and are ten times higher than divergences within E. o. obscura sampled from along a 1500 km Andean transect.  E. o. obscura and E. o. sordida … are best treated as separate species: E. obscura and E. sordida.'  This finding was confirmed in Tang et al. (2018): 'All our analyses delimited E. obscura (from the Andes) and E. sordida (from the Atlantic mountains of Brazil) as well as E. fallax (from Jamaica) and E. cherrei (from Hispaniola) as distinct species in support of previous mtDNA-based proposals to elevate both E. obscura sordida and E. fallax cherrei to species level (Rheindt et al., 2008).'

 

Boesman (2016) showed differences between the (dawn) songs of the two taxa of a magnitude which in the Tyrant Flycatcher family is typically only seen among distinct species. Minns (2017) confirmed Boesman’s findings as to songs and examined the differences in their calls. He showed that the repertoires of both taxa are extensive and that there is minimal overlap between them. The vocal differences demonstrated in these two articles are consistent and in most cases they are sufficient to permit attribution of any single vocalization of the overall repertoire to sordida or obscura with confidence.

 

This is thus a case of two taxa having minor morphological differences and significant genetic and vocal differences, not unlike the case of Elaenia chiriquensis/Elaenia brachyptera, which received a unanimous YES vote for splitting into two species (proposal 686). We even feel the present case to be better supported by evidence, given that numerous recordings of (dawn) song for both taxa are available (vs. only one of the eastern population and none for the western population in the case of E. brachyptera).

 

Recommendation: We recommend a YES vote to split E. obscura and E. sordida as two separate species based on the combined genetic and vocal evidence.

 

English name: The HBW has already split the two taxa, giving E. sordida the English name Brazilian Elaenia (del Hoyo et al. 2018). This is not an ideal name as E. sordida occurs in Paraguay, Argentina and Uruguay, as well as (mainly) Brazil, so we suggest a separate proposal on the English name.

 

Literature cited

Boesman, P. 2016. Notes on the vocalizations of Highland Elaenia (Elaenia obscura). HBW Alive Ornithological Note 131. In: Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from www.hbw.com/node/932054 on 7 October 2018).

del Hoyo, J., Collar, N. & Kirwan, G.M. (2018). Brazilian Elaenia (Elaenia sordida). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/1343699 on 7 October 2018).

Hosner, P.A. 2004. Family Tyrannidae (Tyrant Flycatchers). P. 273 in: del Hoyo, J., Elliott, A. & Christie, D.A. eds. Handbook of the Birds of the World. Vol. 9. Cotingas to Pipits and Wagtails. Lynx Edicions. Barcelona.

Minns, J.C. 2017. Vocal differences in Elaenia obscura. www.xeno-canto.org/article/218

Rheindt, F.E., Christidis, L. & Norman, J.A. 2008. Habitat shifts in the evolutionary history of a Neotropical flycatcher lineage from forest and open landscapes. BMC Evol. Biol. 8: 1193.

Tang, Q., Edwards, S.V. & Rheindt, F.E. 2018. Rapid diversification and hybridization have shaped the dynamic history of the genus Elaenia. Molecular Phylogenetics and Evolution. Volume 127, October 2018, Pages 522-533.

 

Peter Boesman and Jeremy Minns, October 2018

 

 

 

 

Comments from Stiles: “YES. All lines of evidence are consistent with considering sordida a separate species from obscura.”

 

Comments from Areta: “YES. This is a long-awaited split, as morphological and especially vocal differences have been known for a long time. The differences in dawn songs and diurnal call are very marked, as shown by the analysis of Jeremy Minns, which might well merit publication. I would like to see more solid genetic data. The single blood sample of supposed sordida used by Rheindt et al. (2008) comes from a locality until recently apparently not known to be inhabited by sordida (this does not mean that it not present there), and there is no photographic, audio or specimen record to confirm its identification (Jan Kristensen in litt. June 2017). Likewise, I have not seen any type-specimen examination on this front. My concern in cases like this one is the lack of attention to formal taxonomic procedures when taking taxonomic decisions. This is why I think that stability is better served when data is gathered with care, analyzed and properly published. Integrating disparate data to inform our judgments is fine, but nailing down names to types and providing incontrovertible evidence is best.