Proposal (70) to South American Classification Committee

 

Recognize auricularis and velata as separate species from G. aequinoctialis

 

Effect on South American CL: This proposal would split our Geothlypis aequinoctialis into three species, with recognition of trans-Andean auricularis and southern velata as separate species.

 

Background: The bird we treat as one species, Geothlypis aequinoctialis (Masked Yellowthroat), has a disjunct distribution, with the subspecies auricularis and peruviana in western Ecuador and Peru, velata in the tropical/subtropical lowlands south of the Amazon, and nominate aequinoctialis in northern South America. This follows the traditional classification (e.g., Hellmayr 1935, Meyer de Schauensee 1966, 1970, Lowery & Monroe 1968, Hilty & Brown 1986, Ridgely & Tudor 1989, Curson et al. 1994, Sibley & Monroe 1990). The extralimital form chiriquensis of Costa Rica and western Panama is treated as a subspecies of aequinoctialis by most (e.g., Hellmayr 1935, Meyer de Schauensee 1966, 1970, Wetmore et al. 1984, Ridgely & Tudor 1989, Stiles & Skutch 1989, Sibley & Monroe 1990, Curson et al. 1994, AOU 1983, 1998), but as a separate species by some (Lowery & Monroe 1968, Hilty & Brown 1986).

 

Plumage differences among these taxa are unimpressive, even for the perhaps-oversplit Geothlypis yellowthroats. My qualitative impression from skins is that there is more variation among subspecies of North American G. trichas than among the taxa in the aequinoctialis group, even including chiriquensis. Ridgely & Greenfield (1989) kept auricularis as a subspecies of aequinoctialis but noted that the auricularis group "may deserve full species status" and that the "male's facial pattern differs from nominate aequinoctialis group's by at least as much as do presently recognized species of yellowthroats in Middle America." This may be correct, but the difference is nonetheless is only in how far posteriorly the black extends into the auriculars, with auricularis having a truncated extension, more like that of an immature male aequinoctialis (paedomorphic character?).

 

New information: Escalante-Pliego (1992) presented allozyme data from nine species of Geothlypis, with nine population samples from G. trichas and also samples from chiriquensis, nominate    aequinoctialis, and velata. Although she found that the trichas samples differed only slightly and in no geographically coherent way, whereas in aequinoctialis fixed differences were found "between various populations" at two loci. She noted the contrast between high levels of genetic distance among aequinoctialis populations to the conservative phenotypic differentiation. Comparing her (Nei's) genetic distance values to those of other parulids presented by Barrowclough & Corbin (1978), she noted that the values among the aequinoctialis populations were at the level shown by species, not subspecies, i.e., > 0.100, and concluded that the "four allopatric forms of the aequinoctialis complex would seem to deserve species rank."

 

Ridgely & Greenfield (2001) treated auricularis as a species, citing Escalante-Pliego as the reason. They also mentioned that songs of presumed peruviana were "quite different" from auricularis and that yet another species-level taxon might be involved.

 

Analysis: This is a classic case of the problems of changing species limits in the absence of critical evaluation. At the outset, let me make it clear that I have no idea how many species-level taxa are involved in aequinoctialis (much less all those Middle American yellowthroats), and that there may be two, three, four, or more species involved. That being said, there are absolutely no published data that support any change in current taxonomy. First, the allozyme data. As Escalante-Pliego (1992) should have pointed out, those comparative Nei's distance data from Barrowclough & Corbin involved boreal and temperate latitude, highly migratory species of warblers, and as we all should know by now, genetic distance measure of any kind tend to much higher for sedentary tropical birds, often by an order of magnitude. Therefore, any comparative use of those data is flawed. Even within Escalante-Pliego's own data set, she pointed out the influence of sedentary behavior and habitat fragmentation on genetic distances within Geothlypis. Furthermore, general use of genetic distance data for assigning taxon rank is a bucket of problems all of its own that is beyond the scope of current analysis.

 

One naturally wonders about vocalizations in this group. With the tendency of trichas to show strong regional differences in song, one might predict that such differences might be accentuated in tropical resident populations and provide "fuel" for speciation. This indeed may be the case, but not only are direct qualitative comparisons absent, but such an analysis would require careful, quantitative comparisons with special precautions for local dialect formation.

 

Recommendation: Obviously, I vote "NO" on this proposal. The currently published data are so conspicuously deficient that it is discouraging to see taxonomic changes made this way, even if a three-way or more split is eventually justified.

 

Literature Cited:

BARROWCLOUGH, G. F., AND K. W. CORBIN. 1978. Genetic variation and differentiation in the Parulidae. Auk 95: 691-702.

CURSON, J., D. QUINN, AND D. BEADLE. 1994. Warblers of the Americas. Houghton Mifflin.

ESCALANTE-PLIEGO, B. P. 1992. Genetic differentiation in yellowthroats (Parulinae: Geothlypis). Acta XX Congr. Intern. Orn: 333-341.

HELLMAYR, C. E. 1935. Catalogue of birds of the Americas. Field Mus. Nat. Hist. Publ., Zool. Ser., vol. 13., pt. 8.

HILTY, S. L., AND W. L. BROWN. 1986. A guide to the birds of Colombia. Princeton University Press, Princeton, New Jersey.

LOWERY, G. H., JR., AND B. L. MONROE, JR. 1968. Family Parulidae. Pp. 3-93 in "Check-list of birds of the World, Vol. 14" (Paynter R. A., Jr., ed.). Museum of Comparative Zoology, Cambridge, Massachusetts.

MEYER DE SCHAUENSEE, R. 1966. The species of birds of South America and their distribution. Livingston Publishing Co., Narberth, Pennsylvania.

MEYER DE SCHAUENSEE, R. 1970. A guide to the birds of South America. Livingston Publishing Co., Wynnewood, Pennsylvania.

RIDGELY , R. S., AND P. J. GREENFIELD. 2001. The birds of Ecuador. Vol. II. Field guide. Cornell University Press, Ithaca, New York.

RIDGELY, R. S., AND G. TUDOR. 1989. The birds of South America, vol. 1. Univ. Texas Press, Austin.

SIBLEY, C. G., AND B. L. MONROE, JR. 1990. Distribution and taxonomy of birds of the World. Yale University Press, New Haven, Connecticut.

STILES, F. G., AND A. SKUTCH. 1989. A guide to the birds of Costa Rica. Cornell Univ. Press, Ithaca, New York.

 

Van Remsen, October 2003

 

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Comments from Stotz: "NO. I need something other than genetic distance for species recognition."

 

Comments from Robbins: "[NO] I find Van's comments compelling for not supporting the recognition of auricularis and velata as separate species from aequinoctialis."

 

Comments from Jaramillo: "NO _ Leave them as they are for now, pending publication of new data. Note that Patricia Escalante and John Klicka have new information on this complex. She presented some of the data at the NOC in Puyehue. Among the general findings were that Oporornis was polyphyletic, with formosus being in the Geothlypis clade. Within Geothlypis there were two large clades, the small-masked (aequinoctialis and poliocephala groups) and the full-masked (speciosa, rostrata, trichas, nelsoni, flavovelata, beldingi and semiflava). A surprising finding was that chiriquensis (now with aequinoctialis) is actually in the other clade being sister to semiflava which it is geographically closest to. There is also a western and eastern clade within trichas that needs to be resolved, with the western clade including beldingi! The problem is that I can't recall how the different components of aequinoctialis, other than chiriquensis, were related to each other in the cladograms. In any case the good news is that there is brand new data, which may resolve these questions at a later date, bad news is that it isn't published yet."

 

Comments from Zimmer: "I vote "NO". This one has always seemed weak to me, and, again, published analysis is lacking. I'd prefer to wait."

 

Comments from Stiles: "NO for reasons given under D. petechia."

 

Comments from Nores: "NO. Sin subestimar el trabajo de Patricia Escalante, pienso que las razones dadas por Remsen son válidas y hasta tanto no hayan resultados genéticos definitivos, parece mejor conservar el actual ordenamiento."