Dissertation Research: Consequences of Seasonal Variation for Within-Population Genetic Diversity

经调查的自然种群表现出大量的遗传多样性，即个体之间基因组成的差异。这种可变性使种群能够对不断变化的环境做出反应。变异对一个种群来说是至关重要的，因为它允许一个种群进化。环境在时间和空间上的差异被认为是维持这种遗传变异的两个主要因素。空间异质性在一系列环境中很常见，并已被证明支持遗传变异。特定的个体往往能更好地适应它们的微环境，因此整个种群是由许多适应略微不同环境的个体组成的。研究人员将通过实验测试一个种群中的个体是否能更好地适应特定的季节。通过确定个体在一年中的不同时间是否生长和繁殖得更好，他们可以检验这样一种观念，即环境中的时间和空间差异对保持遗传多样性很重要。没有任何利用植物的实验明确地测试了季节或年份之间环境差异的重要性。除了了解支持遗传多样性的潜在机制外，了解植物种群的季节性也可能有实际的好处。例如，除草剂施用的有效性部分取决于在植物生命周期中何时施用除草剂。此外，如果一个种群代表了适应不同季节的一系列基因型，那么特定的个体或种群可能有能力坚持或“预适应”改变的环境。人口对全球环境变化（如变暖）的反应是可以预测的。种群灭绝或遗传变化的预测可以用来检查群落和生态系统中物种组成的潜在变化。

Natural populations which have been surveyed exhibit large amounts of genetic diversity, i.e., differences in the genetic makeup between individuals. This variability allows the population to respond to a changing environment. Variability is crucial to a population because it allows a population to evolve. Differences in the environment through time and space are thought to be two primary factors maintaining this genetic variability. Spatial heterogeneity is common in a range of environments and has been shown to support genetic variability. Particular individuals are often better adapted to their microenvironment, thus the population as a whole is comprised of many individuals adapted to slightly different environments. The investigators will experimentally test if individuals of a population are better adapted to particular seasons. By determining whether individuals grow and reproduce better at different times within the year, they can test the notion that temporal as well as spatial differences in the environment are important in maintaining genetic diversity. No experiments using plants have explicitly tested the importance of environmental differences among seasons or years. In addition to understanding underlying mechanisms supporting genetic diversity, knowledge of the seasonality of plant populations may be of practical benefit. Efficacy of herbicide applications, for example, is partially a function of when during the plant life-cycle an herbicide is applied. Additionally, if a population represents an array of genotypes adapted to different seasons, particular individuals or populations may have the ability to persist in or be "preadapted" to an altered environment. A population's response to a global environmental change such as warming maybe predicted. Predictions of extinction or genetic change by populations may then be used to examine potential shifts in species composition of communities and ecosystems.