Chapter 12 - Finch Communities in a Climatically Fluctuating Environment

Abstract

This chapter is concerned with the change in communities caused by environmental fluctuations and the connection between observable change and change over longer periods of time in the past. Seasonal and annual fluctuations in environmental conditions over periods about decades are well known from direct observation and measurement. Fluctuations in climate, especially temperature, are probably the best known fluctuations for the longest period. In recent years, the records have been extended backward in time through analysis of tree rings, alluvial deposits, ice cores, and coral cores, and it has become apparent that temperature fluctuations display two patterns: periodic or quasi-periodic oscillations and state shifts. The chapter also suggests that the community has a core of species, and that other species are sometimes added or subtracted according to the environmental circumstances. Thus, the biological consequences of extreme climatic conditions experienced during the long-term study provide a view of community dynamics in the historical and prehistorical past.