The underlying assumption of many evolutionary studies is that evolutionary change in developmental processes occurs indirectly, by selection on the characters formed by those processes. While variation among characters must be the result of variation in underlying developmental processes, it is the functioning of those characters that is subject to natural selection. Evolutionary change in development results, but only because these processes give rise to the selected character. In contrast, a little explored aspect of evolution is the possibility that selection acts directly on developmental processes themselves. Because plants grow and develop continuously throughout their lifetime, developmental processes are likely to be critical components of the functioning of these organisms and subject to selection. The alpine tundra presents a particularly intriguing environment in which to explore the results of natural selection on plant development. The alpine is a harsh environment with a very short growing season. Plants have a limited amount of time in which to develop, grow, and reproduce. A common pattern of development in many such environments is preformation. Plants form all structures used during any one growing season during the preceding growing season. These structures remain dormant and unexpanded during the winter and can expand and begin functioning rapidly in the spring. The alpine, however, is also an unpredictable environment. Patterns of snow drift and melt are variable from year to year, drought is common and varies with patterns of snow melt, and snow and freezing temperatures can occur at any time during the growing season. The most common pattern of plant development in such spatially and temporally varying environments is phenotypic plasticity (the ability of an individual to alter its phenotype and development). Thus, in the alpine, plants encounter two conflicting selective regimes both of which are expected to act directly on developmental processes. The short harsh season is expected to select for the predetermined pattern of preformation, while the unpredictability of the environment is likely to select for flexibility of development. These two patterns of development are in direct conflict: preformation is likely to limit any flexibility or developmental response to current environmental conditions. What, then, is the actual pattern of development that has evolved in response to these conflicting demands? The proposed research will examine the developmental properties of preformation and plasticity of plants in the alpine environment. The results will address the issue of the evolution of developmental processes and life histories, and can also be used to predict vegetation response to changing climatic conditions. The Colorado alpine is currently being studied as a model system for examining the effects of global change. Because the alpine is such a harsh and marginal environment, small climatic changes are expected to have dramatic effects on species distribution. A more thorough understanding of the range and limits of developmental responses of alpine plants to environmental variation will provide new and important information for models of vegetation change or persistence.
