Dissertation Research: Local Genetic Differentiation and Adaptation of Quantitative Traits

本提案中概述的研究将检查自交受精的一年生植物Polygonum douglasii种群近亲繁殖的遗传和进化后果。近亲繁殖在动物和植物的自然种群中经常发生，并且有几个重要的遗传后果，它们倾向于通过随机遗传漂变减少种群中的总体遗传变异。近亲繁殖的一种极端形式是植物习惯性地自交种子，而不依赖其他植物的花粉。自交受精的植物种群在野生和作物物种中都很常见。这些种群被认为不包含重要生态性状的遗传变异，因此不能对不同环境下的自然选择作出反应。从这个意义上说，它们被认为是“进化的死胡同”。这种观点尚未得到彻底的验证，但最近的一些理论和实验结果表明，即使在高度自恋的人群中，也可能存在大量的遗传变异。本研究将通过将生态重要性状的遗传分化模式与(1)近交水平、(2)当地环境和(3)单一大种群的当地适应空间尺度联系起来，检验有关遗传变异性和适应特定环境的假设。温室育种实验和田间移植将评估该种群包含足够的遗传变异以适应不同环境的程度。这些实验还将探讨该种群是否实际上适应了该领域的自然环境范围。这项研究将有助于澄清关于近亲繁殖物种进化潜力的许多争议，这些问题对于设计策略以提高许多自交作物物种在广泛环境中茁壮成长的能力具有重要意义。

The research outlined in this proposal will examine the genetic and evolutionary consequences of inbreeding in a population of the self-fertilizing annual plant, Polygonum douglasii. Inbreeding occurs frequently in natural populations of animals and plants, and has several important genetic consequences which tend to reduce the overall genetic variation in a population via random genetic drift. One extreme form of inbreeding is exhibited by plants which habitually self-fertilize their seeds and do not rely on pollen from other plants. Self- fertilizing plant populations are quite common in both wild and crop species. These populations are thought to contain no genetic variability for ecologically important traits and therefore can not respond to natural selection in different environments. In this sense they are thought to be "evolutionary dead-ends." This belief has not yet been thoroughly tested, but some recent theoretical and experimental results suggest that substantial genetic variation may be present within even highly selfing populations. This study will test hypotheses regarding genetic variability and adaptation to specific environments by relating the pattern of genetic differentiation in ecologically important traits to (1) the level of inbreeding, (2) the local environments, and (3) the spatial scale of local adaptation in a single large population of P. douglasii. Breeding experiments in the greenhouse and transplantations in the field will evaluate the extent to which this population contains sufficient genetic variation to adapt to different environments. The experiments will also address whether the population is in fact adapted to a natural range of environments in the field. This study will help to clarify many controversies regarding the evolutionary potential of inbreeding species, issues which are important in designing strategies for improving the ability of the many selfing crop species to thrive in a wide range of environments.