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Download pdf 446KB - FAUNA Paraguay

Download pdf 446KB - FAUNA Paraguay

Download pdf 446KB - FAUNA

April 1994] Short Communications and Commentaries 495 ROBIN, J. P., Y. CHEREL, H. GIRARD, A. GELOEN, AND Y. LE MAHO. 1987. Uric acid and urea in relation to protein catabolism in long-term fasting geese. J. Comp. Physiol. B Comp. Biochem. 157:491-499. WILLIAMS, T. D., K. GHEBREMESKEL, G. WILLIAMS, AND M. A. CRAWFORD. 1992. Breeding and moulting The Auk 111(2):495-499, 1994 fasts in Macaroni Penguins: Do birds exhaust their fat reserves? Comp. Biochem. Physiol. A Comp. Physiol. 103:783-785. Received 29 June 1993, accepted 24 October 1993. Can Avian Distribution Patterns in Northern Argentina be Related to Gallery-forest Expansion-Retraction Caused by Quaternary Climatic Changes? Josf MARIA CARDOSO DA SILVA Zoological Museum, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark Nores (1992) presented an analysis of two bird dis- cation of the refuge model (for review, see Lynch tribution patterns in subtropical South America. The 1988) to a specific point in the subtropical region of first is comprised of disjunct distribution of pairs of South America. Therefore, it must require that the species and subspecies between the southern Yungas taxa involved present distributional concordance as and the Paranaense forests, which are separated by well as rigid ecological fidelity (Vanzolini 1981, Lynch 700 km of xerophytic Chaco vegetation. The second 1988). This problem is even bigger in Chaco, which is a supposed zone of secondary contact located in comprises several different types of forests and woodthe central Chaco, where some "nonforest" species lands (see Ramella and Spichiger 1989). Since Nores and subspecies interact. did not make a clear distinction between the different Nores proposed that both patterns were produced types of forests in the Chaco region, I assume that his by vegetational changes in the central Chaco associ- "forest" within the Chaco region means only "tall ated with the well-supported global climate changes humid gallery forest." during the Quaternary. He suggested that, when this It is implicit in Nores' hypothesis that the presentregion was more humid than today (possibly during day Chaco vegetation represents a major barrier to interglacial periods), forests advanced from the Yun- the dispersion of his forest birds. If this is correct, gas and the Paranaense regions along the Pilcomayo one would expect to find forest birds in this region and Bermejo rivers, forming a wide and continuous only in gallery forests along the rivers. Nores conforest bridge. Forest birds from both regions presum- vincingly showed that this is the case for many of his ably expanded their distributions during this epoch, forest species (see Nores 1992:fig. 3). whereas the ranges of nonforest birds were inter- However, he included in his list of forest birds rupted by this same ecological barrier. The opposite some species that did not fit entirely this situation. occurred when the forest bridge was fragmented dur- Nystalus chacuru is a savanna species (Sick 1985, Silva ing the following drier period. As the forest and non- 1992, Davis 1993). Some species are absent from the forest species sharing the same distribution pattern Argentine Chaco, but occur throughout Paraguayan show different "speciation" levels, Nores proposed and/or Bolivian Chaco and, thus, would not require that these vegetational shifts occurred several times belts of humid forests along the Pilcomayo and Berin the recent past. mejo rivers to reach the Yungas forests. This category There are, however, several fundamental problems of birds includes Pionus rnaximiliani (Smith 1960, Short with the analysis of Nores that cause me to question 1975), Piaya cayana (Short 1975), Veniliornis paserinus the validity of his conclusions. These problems can (Short 1975, 1982), Xenops rutilans (Vaurie 1980), Cyabe grouped in the following major topics: (a) prob- nocorax cyanomelas (Short 1975), Basileuterus culicivorus lems with habitat classification; (b) the authenticity (Short 1975, Ridgely and Tudor 1989, Davis 1993), and of a secondary contact zone in the central Chaco; (c) Hemithraupis guira (Short 1975, Isler and Isler 1987). questionable assumptions; (d) lack of paleoecological Other species (Philydor rufus and Pipraeidea melanosupport. nota) avoid the Chaco region, but are distributed al- Habitat classification.--The first problem with Nores' most continuously from the Yungas forests to the analysis is the lack of a precise definition for forest Paranaense forests throughout central Brazil and and nonforest birds. This is an important point be- southern Bolivia. In fact, this distribution pattern is cause his hypothesis can be considered as an appli- shown so clearly in different groups of birds that

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