9801587 Peterson Spatial scale has been considered carefully in the study of fragmented ecosystems, but the effects of temporal scale have been largely overlooked. Most fragmentation studies focus on anthropogenically fragmented situations that were largely fragmented on a time scale of 101 - 102 yr. This is a time scale within which faunas are expected to still be in the dynamics of relaxation. Naturally fragmented systems, however, provide an opportunity to view older fragmentation schemes ( 103 - 104 yr), potentially allowing analysis of response patterns under equilibrium conditions. The Oaxaca Valley in southern Mexico represents a naturally fragmented ecosystem, ideal for the study of the long-term effects of habitat fragmentation. Twelve thousand years ago, humid pine-oak forest was the dominant vegetation type throughout the region. This forest type is now restricted to high elevations. In the proposed study, the resident bird communities in these relict patches will be inventoried, distribution patterns described and avifaunal variation related to patch characteristics. Distributional data will be compiled using existing historic specimen data, and inventories completed by field inventories. Fragments will be described based on direct field measurement, consultation of thematic maps, and data from remotely sensed imagery. Robust new statistical techniques, which we have tested in anthropogenically fragmented ecosystems, will be applied to understanding influences of temporal scale on effects of fragmentation on avifaunas. Additional analyses will focus on functional groups of taxa, such as feeding guilds, phylogenetic lineages, etc., to provide more detailed understanding of processes involved. Results will be applied to designing a reserve system for maximal preservation of the bird diversity of the ecosystem.
