Proposal (574) to South American Classification Committee
Elevate Knipolegus franciscanus to species rank
Effect on SACC: This would split Knipolegus franciscanus from K. aterrimus.
Background: The current SACC footnote summarizes the situation:
99. Silva & Oren (1992) considered the subspecies franciscanus to be a separate species from aterrimus; see also Ridgely & Tudor (1994). Proposal needed.
Hosner and Moyle (2012) published a species-level phylogeny of Knipolegus, including three of the four Knipolegus aterrimus subspecies (Marañon heterogyna was not available). Knipolegus aterrimus aterrimus and K. a. anthracinus formed a clade sister to K. hudsoni; K. a. franciscanus was recovered sister to K. lophotes + K. nigerrimus. Silva and Oren (1992), Ridgely and Tudor (2009), and van Perlo (2009) already treat K. franciscanus as a species-level taxon based on female plumage differences. Caatinga Black-Tyrant and Sao Francisco Black Tyrant have been used recently for K. franciscanus. Hosner and Moyle recommended Caatinga Black-Tyrant because it is more commonly used (based on Google Searches). However, IOC prefers Sao Francisco Black Tyrant. I do not feel strongly about any English name.
Recommendation: Yes. Maintaining the status quo results in a paraphyletic K. aterrimus; female plumages are distinctive.
Hosner, P. A. and R. G. Moyle. 2012. A molecular phylogeny of black-tyrants (Tyrannidae: Knipolegus) reveals strong geographic patterns and homoplasy in plumage and display behavior. Auk 129: 156-167.
Ridgely, R. S., and G. Tudor. 1994. The Birds of South America, vol. . University of Texas Press, Austin.
Ridgely, R. S., and G. Tudor. 2009. Field Guide to the Songbirds of South America: The Passerines. University of Texas Press, Austin.
Silva, J. M. C., and D. C. Oren. 1992. Notes on Knipolegus franciscanus Snethlage, (Aves: Tyrannidae), and endemism of central Brazilian dry forests. Goeldiana Zoology.
Van Perlo, B. 2009. A Field Guide to the Birds of Brazil. Oxford University Press, New York.
Peter A. Hosner, March 2013
Comments by Remsen: “YES. The genetic data leave no doubt that treatment of franciscanus as a separate species is required.”
Comments from Stiles: “YES. Both to avoid paraphyly and to recognize plumage differences between species in females in a genus in which male plumages are notoriously conservative/similar (as in Cercomacra, for example).”
Comments from Zimmer: YES. The genetic data place franciscanus as sister to two other predominantly Brazilian taxa (lophotes and nigerrimus), which makes a lot more sense biogeographically. Female plumage differences between franciscanus and other members of aterrimus are pronounced. As Gary notes, male plumage in this entire group is very evolutionarily conservative. I would probably cast my vote for São Francisco Black-Tyrant as an English name, although I am used to referring to franciscanus as “Caatinga Black-Tyrant”. “São Francisco” more accurately describes the species’ range, and it fits nicely with the recently described Arremon franciscanus (São Francisco Sparrow). Much of the real caatinga region lies to the north of the range of K. franciscanus.
Comments from Pacheco: “YES. The phylogeny of Hosner and Moyle confirms objectively the long-suspected taxonomic independence of this inhabitant of dry forests from heart of Brazil. This species is not exactly a Caatinga dweller nor is it representative of São Francisco Basin. It is also in the headwaters of the Tocantins River. Perhaps "Snethlage's Black Tyrant" is appropriate.”
Comments from Robbins: “YES. The Hosner and Moyle genetic data clearly demonstrate that franciscanus should be treated as a species.”
Comments from Nores: “YES. Strong genetic data evidence that franciscanus should be treated as a species. Moreover, female plumage differences between franciscanus and other members of aterrimus are distinctive.”