Dissertation Research: Two Modes of Speciation in Coreopsis (Asteraceae): A Chloroplast DNA Study

Coreopsis （Asteraceae）的物种形成有渐进模式和突变模式。两组分化类群的叶绿体DNA将被10个限制性内切酶消化，相应的过滤器将被8个克隆的叶绿体DNA片段探测。在三个逐渐分化的桔梗二倍体形态变种中发现的多样性将用于确定是否在分类品种之间或在其范围的两个主要的，不连续的地理部分之间发生分化。研究人员将对涉及新芽孢松及其衍生物新芽孢松的假定的物种突变事件进行研究，以确定物种内叶绿体DNA多样性的相对数量是否与突变事件相对应，如果是，伴随的种群瓶颈可能有多严重。对cpDNA多样性的初步调查显示了相当大的种间、种群间和种群内的差异。本研究的结果将对涉及两种物种形成模式的遗传过程提供重要的见解，并将证明cpDNA在物种水平以下的多样性分析中的实用性。

Within Coreopsis section Coreopsis (Asteraceae) both gradual and saltational modes of speciation are represented. Chloroplast DNA from both sets of diverging taxa will be digested with ten restriction enzymes, and the corresponding filters will be probed with eight cloned chloroplast DNA fragments. The diversity found within the three gradually diverging diploid morphological varieties of C. grandiflora will be used to determine whether divergence is occurring between the taxonomic varieties or between the two major, discontinuous geographical portions of its range. The presumed saltational speciation event involving C. nuecensoides and its derivative C. nuecensis will be examined to determine whether the relative amounts of chloroplast DNA diversity within the species correspond with a saltational event, and if so, how severe the accompanying population bottleneck may have been. A preliminary survey of cpDNA diversity has revealed considerable interspecific, interpopulational, and intrapopulational variation. The results of this study will give important insights into the genetic processes involved in two modes of speciation, and will demonstrate the usefulness of cpDNA for diversity analyses below the species level.