Proposal (960) to South American Classification Committee

Treat Tolmomyias flavotectus as a separate species from T. assimilis

The SACC note reads:

"76a. Tolmomyias assimilis was formerly (e.g., Cory & Hellmayr 1927) considered a subspecies of T. sulphurescens, but Zimmer (1939a) provided rationale for considering it a separate species, and for treatment of flavotectus of Central America and the Chocó, considered a separate species by Cory & Hellmayr (1927), as a subspecies of T. assimilis. Zimmer (1939a), followed by Pinto (1944), considered flavotectus to have priority over assimilis as the species name, but see <REF>."

Ridgely & Greenfield (2001) for Ecuador and Hilty (2021) for Colombia also split T. flavotectus (W of Andes) from T. assimilis (E of Andes).

Harvey et al. 2020 provided the following tree:

The tree shows that flavotectus (i.e., T. assimilis from Panama) is sister to all the other Tolmomyias and thus distantly related to T. assimilis (presumably including samples of assimilis and sucunduri).

The vocal differences between flavotectus and other taxa are striking (see https://xeno-canto.org/species/Tolmomyias-assimilis and https://xeno-canto.org/species/Tolmomyias-flavotectus; and the brief analysis by Boesman 2016) and the species was lumped without a solid basis. Note however that much variation in vocalizations remains in taxa currently included in T. assimilis, which are out of the discussion here. Separating T. flavotectus seems a safe step forward, while T. assimilis as currently delineated would still include possibly at least 3 species (i.e., assimilis, sucunduri and examinatus/neglectus). At this point, separating T. flavotectus is mandatory, while there is not enough published information to decide on what to do with the remaining T. assimilis taxa.

I recommend splitting T. flavotectus, as done by Cory & Hellmayr (1927), and in agreement with deep genetic differentiation, sister relationship to all Tolmomyias, and vocal differences.

References:

Boesman, P. (2016). Notes on the vocalizations of Yellow-margined Flycatcher (Tolmomyias assimilis). HBW Alive Ornithological Note 121. In: Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. https://doi.org/10.2173/bow-on.100121

HARVEY, M. G., G. A. BRAVO, S. CLARAMUNT, A. M CUERVO, G. E. DERRYBERRY, J. BATTILANA, G. F. SEEHOLZER, J. S. MCKAY, B. C. O’MEARA, B. G. FAIRCLOTH, S. V. EDWARDS, J. PÉREZ-EMÁN, R. G. MOYLE, F. H. SHEDLON, A. ALEIXO, B. T. SMITH, R. T. CHESSER, L. F. SILVEIRA, J. CRACRAFT, R. T. BRUMFIELD, AND E. P. DERRYBERRY. The evolution of a tropical biodiversity hotspot. Science 370: 1343-1348.

J. I. Areta, February 2023

Note from Remsen on English names: Ridgely & Greenfield (2001) used “Yellow-margined Flatbill” for T. flavotectus and “Zimmer’s Flatbill” for T. assimilis. We will need a separate proposal on English names if this one passes, so be thinking about choices.

:

Comments from Remsen: “YES. That flavotectus should be considered a separate species has been known to field people for decades, but without published data on vocalizations, the Zimmer treatment has been perpetuated in most classifications. The new genetic data require that flavotectus be treated as a separate species.”

Comments from Lane: “YES to separating T. flavotectus from the remainder of the T. assimilis group, with the understanding that the latter will no doubt weather more splits in the future once we gain a better understanding of the populations therein.”

Comments from Stiles: “YES to splitting flavotectus from assimilis; probable (?) further splits in assimilis await further data.”

Comments from Zimmer: “YES. As noted in the Proposal, as well as in some of the comments by committee members, there is still more splitting to be done within the wide-ranging assimilis-group, but this is the one split for which there is clear-cut, published, genetic evidence that not only supports a split, but demands it.”

Comments from Claramunt: “YES. The phylogenetic data are robust. This seems yet another case in which lumping by similarity, in the heydays of the polytypic species concept, created polyphyletic species.”

Comments from Robbins: “YES for recognizing flavotectus as a species. Because of the distinct vocalizations, a straightforward decision. Undoubtedly there will be additional splits within the assimilis complex.

Comments from Mario Cohn-Haft (voting for Pacheco): “YES. Splitting out flavotectus from polytypic assimilis is an easy one for me, even not being familiar with the former.  it's not even in the assimilis "complex" according to the gene tree, so that's a YES. What happens in the future to the true assimilis complex isn't part of the issue as far as i can tell.”