Correlations Among Environmental Agents: Implications for Plant Ecology and Evolution

9318523 Miller对自然选择导致物种进化的研究表明，许多令人感兴趣的特征，如叶片形状或生长速度，都是由许多基因座（许多基因）控制的，但人们可以定性地预测在经历自然选择时这些特征将如何进化。例如，以前的研究已经调查了昆虫的食草性如何导致植物物种对食草性的进化变化。然而，很明显，生物体同时受到多种环境因素的影响。例如，沙丘一年生沙巴提亚（Sabatia stellaris）似乎同时受到资源竞争、水分供应和食草性的影响。拟议的研究询问一个主体（如竞争）的选择如何受到第二个主体（如食草）的同时作用的影响。理论预测表明，任何一种因素的选择都会增加，在某些情况下，第二种因素的存在会显著增加。拟议的研究将量化在各种不同的田间试验条件下生长的萨巴蒂亚植物中与竞争、草食和水分胁迫相关的性状选择：竞争、草食、水分胁迫，以及这三种环境因素的几种组合。在每一种环境中，一些已知对应对竞争、草食和/或水分胁迫很重要的植物性状将被量化。通过计算具有这些性状的植物在不同条件下产生的种子，这些性状的选择将在每种环境中量化，并且可以测试预测。本研究结果对于理解不同自然环境下物种的进化速率和遗传多样性的维持等基本问题具有重要意义。它们对于制定或理解农业系统中的育种计划也很重要，因为在农业系统中，完成度和草食性等因素是司空见惯的。

9318523 Miller Studies on the ways in which natural selection leads to the evolution of species have demonstrated that many traits of interest, such as leaf shape or growth rate, are controlled by numerous loci (many genes), but that one can qualitatively predict how traits will evolve when undergoing natural selection. For example, previous research has investigated how herbivory by insects would lead to evolutionary changes in herbivore resistance of a plant species. Clearly, however, organisms are affected simultaneously by multiple environmental agents. The dune annual Sabatia stellaris, for example, appears to be simultaneously affected by resource competition, water availability, and herbivory. The proposed research asks how selection for one agent (e.g. competition) is affected by the simultaneous action of a second agent (e.g. herbivory). Theoretical predictions suggest that the selection by any one agent will be increased, in some cases dramatically, by the presence of any second agent%%% The proposed research will quantify selection for traits related to competition, herbivory, and water stress in Sabatia plants grown under a variety of different experimental conditions in the field: competition only, herbivory only, water stress only, and several combinations of these three environmental agents. In each environment, a number of plant traits known to be important for dealing with competition, herbivory, and/or water stress will be quantified. By counting the seeds produced by plants with these traits under various conditions, selection for these traits will be quantified in each environment and predictions can be tested. The results of this study may be important for understanding basic questions about rates of evolutionary change of species in different natural environments and the maintenance of genetic diversity. They may also be important for developing or understanding breeding programs in agricultural systems where factors su ch as completion and herbivory are commonplace.