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498 Short Communications and Commentaries [Auk, Vol. 11!
and central Brazil (Ratter et al. !978), Bolivia (Davis
!993) and Paraguay (Ramella and Spichiger !989).
There is good evidence that they were more widely
distributed in the past, but only during the dry periods
of the Quaternary (Ab'Saber !988) or Late Tertiary
(Rizzini !979, Ratter et al. !989). Besides, for the
dry river beds sampled by Nores to be interpreted as
evidence of once-continuous gallery forest, it also
would be necessary to suppose that they have approximately
the same age. Considering the extraordinary
dynamics of these rivers, I think this would
be improbable.
In conclusion, I suggest that Notes' article exemplifies
how a biogeographical analysis can be biased
when researchers attempt to fit limited data into a
crude refuge model. In order to fit the model, one
must accept or create many unnecessary and sometimes
questionable assumptions. Such an approach
has been strongly criticized even by proponents of
the refuge model (e.g. Vanzolini 1981, Whitmore and
Prance !987). In the specific example of Nores' analysis,
the author ignored the dynamic geological history
of his study area (Baez and Yah6 1979, Ramella
and Spichiger 1989, Ojeda and Mares 1989, Shapiro
1991, Taylor !99!). Thus, he did not consider the importance
of other events (e.g. Plio-Pleistocene tectonism,
flooding associated with changes in sea level)
that might explain the observed pattern as (or more)
parsimoniously than interpretations based on the refuge
paradigm.
An'SAnER, A.N. 1977. Os dominios morfoclimticos
da Am6rica do Sul. Primeira aproximago. Geomorfologia
52:1-23.
An'SAnER, A.N. 1988. O Pantanal mato-grossense e
a teoria dos reffigios. Rev. Bras. Geogr. 50:9-57.
ADAMOLI, J., E. B. SENNHAUSER, J. M. ACERO, AND A.
RESCIA. 1990. Stress and disturbance: Vegetation
dynamics in the dry Chaco region of Argentina.
J. Biogeogr. 17:491-500.
BAEZ, A.M., AND G. J. S. YANfL 1979. Late Cenozoic
environmental changes in temperate Argentina.
Pages 141-156 in The South American herpetofauna:
Its origin, evolution, and dispersal (W. E.
Duellman, Ed.). Museum of Natural History, Univ.
Kansas, Lawrence.
BARTON, N.H., AND G. M. HEWrrr. 1985. Analysis
of hybrid zones. Annu. Rev. Ecol. Syst. 16:113-
148.
CRACRAFr, J. 1985. Historical biogeography and patterns
of differentiation within South America
avifauna: Areas of endemism. Ornithol. Monogr.
36:49-84.
DAVIS, S. E. 1993. Seasonal status, relative abundance,
and behavior of the birds of Concepci6n,
Departamento Santa Cruz, Bolivia. Fieldiana
Zoologia, n.s. 71:1-33.
ENDLER, J.A. 1977. Geographic variation, speciation
and clines. Princeton Univ. Press, Princeton, New
Jersey.
ENDLER, J. A. 1982. Problems in distinguishing historical
from ecological factors in biogeography.
Am. Zool. 22:44!-452.
FORD, J. 1986. Avian hybridization and allopatry in
the region of the Elnasleigh uplands and Burdekinlynd
divide, north-eastern Queensland. Emu
86:87-110.
HAFFER, J. 1974. Avian speciation in tropical South
America. Nuttall Ornithol. Club No. 14.
HAFFER, J., AND J. W. FITZPATRICK. 1985. Geographic
variation in some Amazonian forest birds. Or-
Acknowledgments.--I thank J. Fjeldsfi, J. Fitzpatrick,
nithol. Monogr. 36:147-!68.
ISLER, M. L., AND P. R. ISLER, 1987. The tanagers:
Natural history, distribution, and identification.
Smithsonian Institution Press, Washington, D.C.
LYNCH, J. D. 1988. Refugia. Pages 311-342 in Analytical
biogeography: An integrated approach to
J. Cracraft, D.C. Oren, F. C. Straube, M. E. Petersen, the study of animal and plant distribution (A.
N. Scharff, C. Rahbek, R. Constantino, and an anon- Myers and P. Giller, Eds.). Chapman and Hall,
ymous referee for useful comments on previous drafts Ltd., London.
of the manuscript. I extend special thanks to G. D. NORES, M. 1992. Bird speciation in subtropical South
Schnell, whose editorial comments greatly improved America in relation to forest expansion and rethe
final version of this paper. My studies are sup- traction. Auk 109:346-357.
ported by Conselho Brasileiro de Desenvolvimento OJEDA, R. g., AND M. g. MARES. 1989. A biogeo-
Cientifico e Techn61ogico (CNPq).
graphical analysis of the mammals of Salta Province,
Argentina. Special Publications, The Museum,
Texas Tech Univ. 27:1-66.
LITERATURE CITED
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RAMELLA, L., AND R. SPICHIGER. 1989. Interpretaci6n
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