Proposal (240) to South American Classification Committee
Recognize Percnostola [Schistocichla] saturata (Thamnophilidae) as a species separate from P. leucostigma
Taxonomic history of saturata:
Salvin (1885) originally described the eastern tepui saturata as a species, but Cory and Hellmayr (1924) treated it as conspecific with leucostigma and both were treated as subspecies of Sclateria schistacea. Although Todd (1927) never examined a specimen of saturata, he treated it as a species in his newly erected genus Schistocichla. Based on sympatry, Zimmer (1931) treated leucostigma and schistacea as species, and both Zimmer (1931) and Chapman (1931) considered saturata as a subspecies of leucostigma. Because of the lack of new information on this range-restricted taxon, saturate has been maintained as a subspecies of leucostigma.
Braun et al. (2005 - pdf available from Robbins) demonstrated based on plumage, morphometrics, vocalizations, and genetics that saturata is quite distinct from leucostigma. The two are parapatric, with saturata replacing the lowland inhabiting leucostigma at the base of the eastern tepuis. This elevational replacement of closely related taxa is now appreciated for a number of eastern tepuis taxa.
Although morphological differences are subtle (e.g., both male and female are darker in respective plumage coloration than nominate leucostigma; male saturata have all black bills, whereas the mandible in male leucosticta is pale at the base; statistically significant differences between males in wing and exposed culmen length), the loud song is quite distinct between the two taxa (Braun et al. 2005). Based on 2064 bp of mtDNA (ATPase 6, ND2, and ND3), sequence divergence between saturata and leucostigma samples averaged 9 % (range 8.8%-9.1%, 200 comparisons). To put the molecular data in context, P. schistacea is 10 % divergent from saturata and leucostigma (Braun et al. 2005).
In summary, the morphological, vocal, and genetic data clearly demonstrate that saturata be recognized as a species. The authors suggested the English name, Roraiman Antbird for saturata given that there is no distinctive morphological character and Chubb (1921) used the name Roraiman Ant-creeper. The name Tepui Antbird would not be appropriate as saturata appears to be restricted to the easternmost tepuis. I strongly support the recognition of saturate as a species and the English name Roraiman Antbird.
Braun, J.M., M.L. Isler, P.R. Isler, J.M. Bates and M.B. Robbins. 2005. Avian speciation in the Pantepui: the case of the Roraiman Antbird (Percnostola [Schistocichla] "leucostigma" saturata). Condor 107:327-341.
Chapman, F.M. 1931. The upper zonal bird-life of Mts. Roraima and Duida. Bull. Am. Mus. Nat. Hist. 63:1-135.
Chubb, C. 1921. The birds of British Guiana. Vol. 1 (1916), Vol. 2 (1921). Bernard Quaritch, London.
Cory, C. and C.E. Hellmayr. 1924. Catalogue of birds of the Americas. Pteroptochidae-Conopophagidae-Formicariidae. Field Museum of Natural History, Zoological Series 13, part 3:1-369.
Salvin, O. 1885. A list of the birds obtained by Mr. Henry Whitely in British Guiana. Ibis 1885:418-439.
Todd, W.E.C. 1927. New gnateaters and antbirds from tropical America, with a revision of the genus Myrmeciza and its allies. Proc. Biol. Soc. Wash. 40:149-178.
Zimmer, J.T. 1931. Studies of Peruvian birds. I. New and other birds from Peru, Ecuador, and Brazil. Am. Mus. Novitates 500:1-23.
Mark Robbins, August 2006
Comments from Stiles: "YES. Braun et al. present a battery of convincing arguments for recognizing saturata as a species."
Comments from Zimmer: "YES. These are clearly two different species, as evidenced not only by strong vocal differences in loudsongs, but also by elevational parapatry. The two forms occur within 10 km or so of one another along the Escalera road in SE Bolívar, Venezuela. A vocal analysis by Isler et al (in press) of the entire leucostigma complex lends further support to the already published paper by Braun et al."
Comments from Stotz: "YES, although I should note that leucostigma will probably need to be further split. But that is not a strong argument for leaving saturata in leucostigma."
Comments from Jaramillo: "YES - solid data and analysis."
Comments from Pacheco: "YES. Os resultados da análise do repertório vocal por Isler, Isler, Whitney & Zimmer (Wilson J Orn 119:53-70) são consistentes com este estudo abrangente de Braun et al. e reforçam o arranjo aqui proposto."