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.
Lit Cit:
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: " NO. 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: "NO -- vocal comparisons are
needed to ascertain whether johnsoni deserves species rank."
Comments from Schulenberg: "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: "NO. 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 don´t 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."