Optimal Reaction Norms and Genetic Constraints in the Evolution of Plant Size in Ipomoea purpurea

小行星9707223 该项目的目标是试图了解模式生物牵牛花Ipomorea purpurea最佳适应其遇到的各种环境的程度。 具体而言，该项目旨在根据经验确定不同环境中几个性状的最佳值，然后确定自然种群是否已经进化到在各自的环境中表现出这些值。 该项目还试图确定可能阻止种群进化到这些最佳值的任何制约因素。 自然环境的特点，通常遇到的I。将首先对purpurea进行调查。 利用这些信息，将进行两个田间试验，其中我。紫花苜蓿是在土壤养分水平梯度或竞争强度梯度上生长的。 自然选择作用于与植物生长和大小有关的性状的模式将被测量，以确定这些性状的平均值在每个环境中离它们的最佳值有多远。 一组育种和选择实验将提供任何遗传约束的表征，以防止向这些最优进化，这些约束的重要性将通过计算机模拟进行评估。 自然选择的进化是在什么是有利的（选择如何起作用）和什么是可能的（由生物体的遗传学决定）之间的妥协。虽然生物学家在理解生活在简单受控环境中的模式生物（例如果蝇）的进化方面取得了很大进展，但对植物和动物种群对复杂自然环境的进化反应知之甚少。 这个项目的广泛目标是开始提供一个了解这种反应的生物体，通常遇到一个复杂的环境。

9707223 Rausher The goal of this project is to attempt to understand the degree to which a model organism, the morning glory Ipomorea purpurea, is optimally adapted to various environments it encounters. Specifically, this project seeks to characterize empirically the optimal value for several traits in different environments and then determine whether natural populations have evolved to exhibit those values in the respective environments. The project also seeks to characterize any constraints that may prevent populations from evolving to those optimal values. Characteristics of the range of natural environments normally encountered by I. purpurea will initially be surveyed. Using this information, two field experiments will be conducted in which I. purpurea is grown either a gradient of soil nutrient levels or a gradient of competitive intensity. The pattern of natural selection acting on traits related to plant growth and size will be measured to determine how far the means of these traits are from their optima in each environment. A set of breeding and selection experiments will provide a characterization of any genetic constraints acting to prevent evolution toward these optima, and the importance of these constraints will be evaluated by computer simulation. Evolution by natural selection is a compromise between what is favored (how selection acts) and what is possible (determined by the genetics of organisms). While biologists have made great strides understanding evolution in model organisms (e.g. fruit flies) living in simple, controlled environments, much less is known about the evolutionary responses of plant and animal populations to complex natural environments. The broad aim of this project is to begin to provide an understanding of such a response in an organism that typically encounters a complex environment.