BIOGEOGRAPHY OF NEOTROPICAL BIRDS - CONCEPTUAL HIERARCHIES AND PROSPECTS FOR FUTURE-RESEARCH

The Neotropical Region is defined here as the area from about the Trop ic of Cancer in Mexico south through Central America to Panama, the wh ole of South America south to the Cape Horn archipelago, and the archi pelagos of the West Indies and Galapagos. The ornithological literatur e on the neotropical fauna could be reviewed in order to analyze the v arious elements of the fauna and to trace their respective origins in time and space. However, in the present paper this literature is revie wed instead from the point of view of hierarchic levels of analysis an d of hierarchic levels of perception. After a summary of the data base used for biogeographic studies on neotropical birds (paleontogical, t axonomical, distributional, and ecological data), three conceptual fra meworks are described. The first organizes biogeography into three lev els: historical, ecological, and theoretical. In the second scheme con ceptual units are integrated into four spatio-temporal levels which co rrespond to four domains of biogeography: non-interactive equilibrium, assortative equilibrium, evolutionary or speciational equilibrium, an d paleontological or paleobiogeographic equilibrium. The third framewo rk contains a hierarchy of five levels of spatial perception of biogeo graphic phenomena: the station, the biotope, the sector, the region, a nd the continent. Two examples taken from studies in the high Andean p aramo and puna biomes illustrate graphically and concretely the hierar chic nature of biogeographic processes. Finally, a research program is proposed for long-term projects feasible from research centers locate d in the Neotropical Region and manned by resident personnel. The five -level spatial hierarchy permits one to carry out local studies at a l arge map scale as well as more global projects at a smaller map scale. The choice of project and of level(s) of approach must be dictated by the personnel, financial and technical resources available to a given research center. Such a hierarchic organization should permit cross-f ertilization between and among various levels (and of course between a nd among the various questions asked at each level). Consequently, inv estigators working at different levels should be able to integrate the ir studies yet maintain the uniqueness of their proyect.