Split Drymophila caudata into four species
Effect on SACC: If adopted, three species would be added to the South American checklist by splitting Drymophila caudata into four species, as recommended by Isler and colleagues (2012): D. klagesi Hellmayr and Seilern, 1912, D. hellmayri Todd, 1915, D. caudata (Sclater, 1854), and D. striaticeps Chapman, 1912.
Background on a taxonomic conundrum: Not included in the Isler et al. paper is a full description of the taxonomic history of Drymophila caudata. Sclater (1854) described Formicivora caudata based on “Bogota” trade skins. He described the male as having the middle of pileum and nape solid black and a heavily streaked plumage overall. These characteristics are clearly depicted in the plate of the description (http://bit.ly/RDy9Os). Isler et al. (2012) had access to the syntypes at BMNH and could confirm these diagnostic traits.
Almost six decades after the description of caudata, Hellmayr and Seilern (1912) described Drymophila caudata klagesi from Venezuela, a taxon that also has a solid black middle pileum as in D. c. caudata but that differs in other respects. However, Hellmayr and Seilern used as comparative material for nominate caudata three male specimens with striped crowns: two “Bogotá” skins and one from Santa Elena, Antioquia, Colombia (Central Andes). Clearly, Hellmayr assumed that the “Bogotá” skins in front of him (sent by A. Menegaux from the Paris Museum) corresponded to true caudata (i.e. topotypical), but this was not the case. There is no a single indication in the literature that the syntypes of caudata at the BMNH were actually examined for this or any other descriptions or studies that followed.
That same year Chapman (1912) described D. c. striaticeps as a subspecies distinct from D. c. caudata as his specimens from the Western and Central Andes of Colombia exhibited completely striped (black and white) crowns unlike what the Sclater’s description indicated for nominal caudata. Chapman was looking at male specimens that appeared as those that Hellmayr and Seilern assumed to be of the nominal form. Although Chapman did not inspect the syntypes of caudata at the BMNH directly, he was guided by Sclater’s description and thought that two adult males from Santa Marta, which also have black crowns, corresponded to nominate caudata (Chapman 1912, p. 146). Chapman was in the right direction but apparently was not aware at that point of the interpretations of Hellmayr and Seilern written in the D. c. klagesi description.
In 1915, Todd described D. c. hellmayri from Santa Marta as a subspecies of D. caudata (Todd 1915, p. 80) and argued that its diagnostic characters included the black middle crown and nape indicating that, according to a personal comment by C. E. Hellmayr, “in typical D. c. caudata these parts are always prominently streaked with white, except in worn plumage”. This assertion clearly contradicted Sclater’s original description (of caudata) and casted doubts on the validity of Chapman’s striaticeps. Further data on Santa Marta birds resulted in a better characterization of the local form of this antbird (D. c. hellmayri) by Todd and Carriker (1922), particularly, for its unique rufous-brown tone of the tail. A long quote of C. E. Hellmayr in Todd and Carriker’s monograph (p. 307) reveals a number of conclusions that were not verified at the time but that resulted in a great deal of confusion, ultimately obscuring the diversity of this group of antbirds: “Drymophila caudata striaticeps Chapman is simply D. c. caudata redescribed. Mr. Chapman was misled by the original description and accompanying figures. Adult males from Bogota (topotypical) and the Western Andes of Colombia (striaticeps), [for which] I have examined a series in the Paris Museum, are perfectly identical inter se and have the top of the head regularly streaked with white. In breeding time the white edges sometimes become nearly obsolete. It must have been such a specimen that served as type of Sclater's description. Birds from western Ecuador agree in every respect with the Colombian ones”. Isler and colleagues (2012) found this to be incorrect, a mistake stemming from “Bogotá” trade skins in different museums from different regions in Colombia, where the diversity of this group of antbirds is concentrated.
Chapman added to the confusion when he wrote (1917, p. 378): “in the absence of topotypical specimens I was led to believe, both by Sclater's original description and plate, as well as by his description in the British Museum Catalogue, in which it is said the "centre of the cap is black," that true caudata had the cap black and, consequently, that Santa Marta males, in which the cap is black represented this form. Hence the birds from western Colombia with a striped crown were described under the name striaticeps. Hellmayr, however, writes me that the type, as well as other Bogota specimens, which he has examined, have the crown striped, and are not separable from Ecuadorian specimens. It follows, therefore, that striaticeps becomes a synonym of caudata, from which the black-crowned Santa Marta bird is separable”.
Other subspecies were described in the 20’s and 30’s from the Andes of Ecuador Peru and Bolivia, all with males with striped crowns. Carriker (1935, p. 324) when describing the subspecies boliviana argued against Hellmayr’s interpretation by stressing that: “Contrary to the views of Dr. Hellmayr, I think that striaticeps Chapman, is a perfectly good race […]. The males differ from caudata in having the whole pileum heavily streaked with white, while in caudata the median portion of the pileum and occiput is pure black […and by having] much heavier streaking on the throat and chest.” Nonetheless, striaticeps continued to be treated as a junior synonym of caudata, the newer more southern forms were also synonymized with caudata (see Peters 1951, p. 210), leading to the taxonomy of three subspecies recognized until today: caudata, hellmayri and klagesi (Zimmer and Isler, 2003) in addition to the more recently introduced aristeguietana from Serranía de Perijá (Aveledo H. and Pérez C., 1994). None of the subspecies of Drymophila caudata has ever been treated as separate species.
New published information: Isler et al. (2012) conducted a study combining data on phylogeography, vocalizations, geographic plumage variation, including the syntypes of D. caudata caudata, and environmental and elevational distributions to attempt to resolve this taxonomic conundrum, to assess species limits, and to study the biogeography of differentiation of these montane antbirds. These authors uncovered the confusion outlined above and concluded that the description by Sclater is indeed accurate and that the syntypes are clearly distinct from all other subsequently named forms in this group, including the other two black capped taxa klagesi and hellmayri, and even more so from the streaked capped striaticeps (contra Hellmayr). The authors found support for recognizing four valid species-level taxa.
Male specimens of the four species recommended by Isler et al. (2012). Photos courtesy H. V. Grouw and J. P. López.
The four major lineages recovered in the molecular analysis corresponded to four major, divergent, vocal and plumage groups to the level that these were recommended for recognition as separate species. Some of these species are also divergent in their ecological and elevational ranges – with hellmayri and klagesi found at more foothill elevations than the upper montane species caudata and striaticeps. All the details of the analyses and rationale behind the taxonomic recommendations can be found in the paper whereas the map in Fig. 1 depicts the occurrence records of the four species:
- Drymophila klagesi (Hellmayr and Seilern, 1912) - Klages’s Antbird. Venezuela and NE Colombia in Serranía de Perijá and the northern Eastern Andes in depto. Norte de Santander.
- Drymophila hellmayri (Todd, 1915) - Santa Marta Antbird. Colombia, endemic to the Sierra Nevada de Santa Marta.
- Drymophila caudata (Sclater, 1854) - Long-tailed Antbird. Colombia, endemic to the western slope of the Eastern Andes and the Upper Magdalena valley in Caquetá and Huila.
- Drymophila striaticeps (Chapman, 1912) - Streak-headed Antbird. Colombia, Ecuador, Peru, and Bolivia along the main Andean cordillera.
The region of provenance of the syntypes is discussed by Isler et al (2012, p. 580). Given all the information available to the authors they deduced that the syntypes corresponded to one of the four proposed species recovered in their analysis, the one that is distributed in the western slope of the Eastern Andes south to the Upper Magdalena valley in Caquetá and Huila, Colombia. The authors did not declare a particular locality for the syntypes in the strict sense nor they designated new types either. The map (Fig. 1) is explicit in their take on the provenance of the syntypes, and it parallels their conclusion: "...and it appears likely that the types of caudata came from somewhere in this area, probably Santander". “Bogotá” skins were collected in various regions of Colombia (hence, the presence of streaked and unstreaked-headed Drymophila specimens). Chapman's account on the history of “Bogotá” collections is compelling and continues to be the most important study of these collections (1917, p. 13-15); he explained that among the areas of origin of “Bogotá” skins included southern Santander and the upper Magdalena Valley in San Agustin – areas were Isler et al. (2012) had modern specimens and vocal samples indicating a species-level divergent lineage, i.e. D. caudata sensu stricto. Given all available information, I think that there is no other region in South America where the syntypes of caudata could have come from other than that stretch of the western slope of the Eastern Andes where the sampling gaps still remain large. Hopefully, modern specimens and data from this region are made available sometime soon and confirm this conclusion.
Recommendation: I recommend a YES vote to recognize these species limits and English names.
Isler, M. L., A. M. Cuervo, G. A. Bravo, & R. T. Brumfield. 2012. An integrative approach to species-level systematics reveals the depth of diversification in an Andean thamnophilid, the Long-tailed Antbird. Condor 114: 571–583
Other references therein and in the SACC bibliography.
(PDFs of the original description papers and monographs can be freely accessed on BHL and other such sites, or are also available upon request, including a translation to English of the description of D. c. klagesi).
Andrés Cuervo, September 2012
Comments from Stiles: “YES. A really interesting and thoughtful piece of work!”
Comments from Remsen: “YES. Good vocal evidence for 4 species-level taxa.”
Comments from Zimmer: “YES. Nice concordance between vocal, morphological, molecular, and ecological data sets. The extent of the vocal differences alone between the four groups provides sufficient evidence for splitting along the lines proposed by the authors.”
Comments from Thomas Donegan: “We recently assessed these splits for the Colombian checklist and accepted all of them. Some comments on sampling issues and gaps which affect some of the newly split species and photographs in life of most of them are set out in the paper linked below and may be of interest.
“Reference: Donegan, T.M., Quevedo, A., Salaman, P. & McMullan, M. 2012. Revision of the status of bird species occurring or reported in Colombia 2012. Conservación Colombiana 17: 4-14. http://www.proaves.org/proaves/images/RCC/Con_Col_17_1-14_Actualizacion_Listado.pdf”
Comments from Pacheco: “YES. A consistent suggestion. A minor correction about the indication of name and authorship: the authorship must remain in parentheses only in Drymophila caudata (Sclater, 1854) because it was originally described in different genus. That is not the case in other three.”
Comments from Nores: “YES. Good concordance between molecular, vocal and morphological evidence.”