Collaborative Research: Understanding the Roles of Natural Selection and Evolutionary Constraints in the Maintenance of Invariant Floral Traits.

9903880一致生物多样性的一个显著特征是在比较生物特征时观察到的模式。虽然有些特征表现出相当大的变异性，可以唯一地识别种群中的个体，但其他特征的变异性较小，并被相关物种的大群体所共享。尽管生物学家早就认识到变异作为未来进化的原材料的重要性，但对变异有时可能缺乏的原因研究较少。这种变异的缺乏可能是由于缺乏遗传变异或与其他性状的遗传相关性导致的对进化的限制。或者，缺乏变异可能是因为自然选择消除了不适合的变异，并保持了一小部分能很好地适应环境的特征。在这项研究中，一种温室人工选择和田间自然选择研究的新组合将被用来确定限制或选择是否导致两组花性状的低水平变异。本研究将以野生萝卜(Raphanus Raphanistrum Brassicaeae)为材料，从花药形态、花药长短比和花冠外长花丝伸展程度两个方面进行研究。通过这项研究产生的对约束和选择的基本理解可能适用于理解各种应用的进化问题，例如作物和野生物种是否能够迅速适应全球气候变化，濒危物种的保护(通常缺乏遗传变异)，以及病原体和害虫对抗生素、农药和除草剂的抗药性的进化。

9903880ConnerA remarkable property of biological diversity is the patterning that is observed when characteristics of organisms are compared. While some features show considerable variation and can uniquely identify individuals within a population, other traits are less variable and are shared by large groups of related species. Although biologists have long recognized the importance of variation as the raw material for future evolution, the reasons why variation may sometimes be lacking are less often studied. This lack of variation could be due to constraints on evolution, caused by a lack of genetic variation or by genetic correlations with other traits. Alternatively, the lack of variation could result from natural selection eliminating unfit variants and maintaining a narrow range of traits that are well-adapted to the environment. In this research, a novel combination of artificial selection in the greenhouse and studies of natural selection in the field will be used to determine whether constraints or selection cause the low levels of variation found in two sets of floral traits. The research will be done using the wild radish (Raphanus raphanistrum Brassicaeae) and two aspects of anther morphology, the ratio of long- and short-filament lengths and the extent of long-filament exertion beyond the corolla. The basic understanding of constraints and selection generated by this research may be applicable to understanding a variety of applied evolutionary problems, such as whether crops and wild species can adapt rapidly to global climate change, conservation of endangered species (which often lack genetic variation), and the evolution of resistance to antibiotics, pesticides, and herbicides by pathogens and pests.