Proposal (28) to South American Classification Committee
Recognize johnsoni as a separate species from Pseudocolaptes lawrenceii
Effect on South American CL: this proposal would split out the subspecies johnsoni from Pseudocolaptes lawrenceii (and therefore limit the distribution of the latter to Central America and remove it from SACC list).
Background: With complex age, individual, and geographic plumage variation in Pseudocolaptes, it's no wonder that taxonomy within the genus has had a complex history. For example, although perhaps a low-point, the taxon johnsoni of the Western Andes of Colombia and Ecuador was thought by Vaurie (1980) to represent an immature plumage of boissonneautii, despite Zimmer (1936) having already correctly defined its separate range; Zimmer concluded that it was a subspecies of lawrenceii, and that classification was followed by most subsequent authors (Peters, Meyer de Schauensee).
New information: Robbins and Ridgely (1990) suggested that johnsoni deserved recognition as a separate species. They based this primarily on its substantially lower elevational distribution, 900-1500 m. They wrote: "Differences in elevational preferences between johnsoni and nominate lawrenceii are as great as they are between johnsoni and boissonneautii." They also noted plumage characters that allow a diagnosis of johnsoni from lawrenceii, namely that it is a darker rufous throughout. They pointed out that johnsoni and boissonneautii were elevationally separated, perhaps even parapatric, on the western slope of the Andes in Ecuador. They remained cautious, however, because of an absence of knowledge of vocal differences between johnsoni and nominate lawrenceii (and in fact treated johnsoni under the heading of Pseudocolaptes lawrenceii).
Ridgely & Tudor (1994) and Ridgely & Greenfield (2001) treated johnsoni as a separate species from lawrenceii based on Robbins & Ridgely (1990), but did not provide any additional information.
Recommendation: I don't think the evidence is particularly strong either way in this situation, but I recommend a NO vote on this proposal because:
(1) Although the near parapatry of johnsoni and boissonneautii in Ecuador is sufficient evidence in my opinion for treating them as separate species, it does not directly affect this proposal, namely whether johnsoni should be treated as a separate species from Central American lawrenceii.
(2) The lower elevational distribution of johnsoni relative to lawrenceii is, I suspect, only a consequence of depression of elevational zones on the very humid western slope of the Western Andes, which, as I understand it, is a well-known trend, with many "montane" species found within a few hundred meters of sea level. Perhaps the presence of boissonneautii on same slope (a unique situation in the genus) also prevents it from extending higher (rather than any intrinsic limitation to lower elevations). Therefore, I don't think this is a "species level" character, especially given the flexibility of elevational ranges of many Andean birds.
(3) I hesitate to split allopatric populations without a rigorous comparison of vocal differences.
(4) The plumage differences, namely darker, more saturated pigmentation of johnsoni relative to lawrenceii, are not sufficient in themselves for taxon-ranking, especially with Gloger's Rule predicting a darker plumage in Pacific slope johnsoni. (On the other hand, P. lawrenceii and P. boissonneautii also differ primarily in coloration and degree of streaking.)
(5) Although the ranges of johnsoni and lawrenceii are disjunct, so are those of some other montane furnariids currently treated at the subspecies level, e.g., in Premnoplex brunnescens and Syndactyla subalaris.
English name: Ridgely & Tudor (1994) and Ridgely & Greenfield (2001) used "Pacific Tuftedcheek" for johnsoni. If we split it, I suppose we should follow this for reasons of stability, but I personally don't like application of "Pacific" to any non-marine bird.
Ridgely, R. S. & P. J. Greenfield. 2001. The birds of Ecuador. Vol. I. Status, distribution, and taxonomy. Cornell University Press, Ithaca, New York.
Ridgely, R. S. & G. Tudor. 1994. The bird of South America. Vol. II. The suboscine passerines. University of Texas Press, Austin, Texas.
Robbins, M. B., & Ridgely, R. S. 1990. The avifauna of an upper tropical cloud forest in southwestern Ecuador. Proc. Acad. Nat. Sci. Philadelphia 142: 59-71.
Vaurie, C. 1980. Taxonomy and geographical distribution of the Furnariidae (Aves, Passeriformes). Bulletin of the American Museum of Natural History 166: 1-357.
Zimmer, J. 1936. Studies of Peruvian birds, no. 21. Notes on the genera Pseudocolaptes, Hyloctistes, Hylocryptus, Thripadectes, and Xenops. American Museum Novitates 862: 1-25.
Van Remsen, 20 May 2003
Addendum from Remsen: I forgot to mention in original proposal that in 1996 the AOU checklist Committee considered a rejected an official proposal to recognize johnsoni as a separate species.
Comments from Zimmer: "I vote "NO" on this one. I'm not impressed by the differences in elevational distribution for the same reasons cited by Van, and Van's examples of Premnoplex and Syndactyla address the issue of allopatry nicely. I would not be surprised if johnsoni does prove to be a species separate from nominate lawrenceii, but lacking any data on vocal comparison, it seems premature to make such a change. The morphological distinctions between the two taxa are not of themselves impressive, and given the allopatric distributions, I think that some kind of vocal analysis is needed."
Comments from Robbins: "I vote "no" on this -- vocal comparisons are needed to ascertain whether johnsoni deserves species rank."
Comments from Schulenberg: "My vote: "No". I don't have very strong feelings either way, mostly out of ignorance. Johnsoni geographically overlaps with boissonneautii, with elevational segregation, so we can feel confident that these two are distinct.
"Zimmer stated that "its [johnsoni] affinities are close to lawrenceii", but I'm not sure that he explained what he meant by that or what led him to that conclusion. To my eyes lawrenceii looks more like boissonneautii than does johnsoni. I could see recognizing three species, or if two, then boissonneautii (including lawrenceii) and johnsoni, as easily as I could see recognizing the standard two, boissonneautii and lawrenceii (including johnsoni). So, my vote is less a statement that I think that Zimmer, Peters and Meyer de Schauensee had it right than a plea that someone, sometime examine geographic variation across the board (multiple taxa, multiple characters)."
Comments from Stotz: "I vote to keep Pseudocolaptes johnsoni in lawrenceii. There is no evidence that I can see that suggests that it is a separate species, although it could be. I fall back on the status quo."
Comments from Stiles: "NO. Probably correct but we need the evidence up front; in this case while I definitely agree with the proposal, having had experience with all three forms, I donęt have sonograms (etc.) and will suspend personal opinion in the interests of being consistent with stated principles."
Comments from Jaramillo: "NO. Perhaps all three are good species, but there is no good data on voice available particularly comparing johnsoni and lawrenceii. I suggest we keep johnsoni in lawrenceii until data are published."