ROW/RPG: Developmental Plasticity in Polygonum viviparum

许多进化论研究的基本假设是，发育过程中的进化变化是通过对这些过程形成的特征进行选择而间接发生的。虽然字符之间的差异必须是潜在发育过程中差异的结果，但这些字符的功能受到自然选择的影响。发展结果的进化变化，但仅仅是因为这些过程产生了选定的特征。相比之下，进化的一个很少被探索的方面是选择直接作用于发育过程本身的可能性。由于植物在其一生中不断生长和发育，发育过程很可能是这些有机体功能的关键组成部分，并受到选择的影响。高山冻土带提供了一个特别耐人寻味的环境，在这里可以探索自然选择对植物发育的结果。阿尔卑斯山是一个生长季节很短的恶劣环境。植物发育、生长和繁殖的时间有限。在许多这样的环境中，一种常见的发展模式是预习。植物构成了在前一个生长季的任何一个生长季中使用的所有结构。这些结构在冬季保持休眠和不扩张，并可以在春季迅速扩张和开始运作。然而，阿尔卑斯山也是一个不可预测的环境。积雪和融化的模式每年都是不同的，干旱很常见，随着积雪融化的模式而变化，在生长季节的任何时候都可能出现降雪和冰冻温度。在这种时空变化的环境中，植物最常见的发育模式是表型可塑性(个体改变其表型和发育的能力)。因此，在高山地区，植物会遇到两种相互冲突的选择机制，这两种机制都有望直接作用于发育过程。预计短暂的严酷季节将选择预先确定的形成模式，而环境的不可预测性可能会选择发展的灵活性。这两种发展模式是直接冲突的：预先形成可能限制对当前环境条件的任何灵活性或发展反应。那么，为回应这些相互冲突的需求而演变的实际发展模式是什么？这项拟议的研究将考察高山环境中植物的前期形成和可塑性的发展特性。这些结果将解决发育过程和生活史的演变问题，还可以用来预测植被对不断变化的气候条件的反应。科罗拉多州的高山山脉目前正在被作为检验全球变化影响的模型系统进行研究。由于高山是如此恶劣和边缘的环境，微小的气候变化预计会对物种分布产生巨大影响。更深入地了解高山植物对环境变化的发育反应的范围和限度，将为植被变化或持续性模型提供新的重要信息。

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.