Dissertation Research: Speciation Processes in Serpentine Endemics: A Molecular Systematic Study of the Streptanthus glanduloses Complex (Cruciferae)

稀有和特有物种提供了独特的研究机会 物种形成的原理和过程。 关于Streptanthus glandulosus complex（Cruciferae）是一组蛇纹石 地方性流行病，其中大多数是罕见的或受到威胁的。 这个复杂 是一个特别突出的例子， 在种群和分类群的分歧基板。 这些 一年生植物以间断种群出现在蛇纹土上 从特哈马县到圣路易斯的加州海岸山脉 奥比斯波县，被不合适的地区所隔离， 非蛇纹岩栖息地 这种隔离，伴随着 近亲繁殖，可能导致了许多不同的表型 在每个物种内的种群中可识别。 的 该群体的进化史是未知的，分类学上的界限是 争议：从一个物种的三个变种到13个不同的 物种已被确认。 因此，S.腺肌复合体 不仅需要系统的研究， 一个很好的论坛，在那里研究物种形成过程， 蛇特有种 基于种群间杂交 Kruckeberg（1957）的实验表明， 在复杂的种群的干涉性和 他们被分开的距离。 我们建议， Kruckeberg对距离隔离的经典研究使用了 酶电泳和限制性位点的组合 分析叶绿体DNA以检查遗传差异， 系统关系和进化过程。 的 具体目标是：（1）评估等位酶和cpDNA 居群间分化及相关遗传分化 （2）建立地理格局; 使用cpDNA限制性位点数据的复合物，并使用 为了评估古特有现象和新特有现象的假定实例， 从分布较广的类群中最近衍生出的有限类群， 和反复适应的蛇纹耐力;（3）估计 使用等位酶数据的种群间基因流动水平; (4)比较限制性和限制性等位酶变异性水平， 广布的分类群。 干涉性、等位酶、 和限制性酶切位点分析。腺肌复合体 提供了一个几乎无与伦比的研究场所 物种形成过程，并将提供必要的信息 对建筑群进行合理管理。

Rare and endemic species provide unique opportunities to study the principles and processes of speciation. The Streptanthus glandulosus complex (Cruciferae) is a group of serpentine endemics, most of which are rare or threatened. This complex represents a particularly striking example of the role of substrate in the divergence of populations and taxa. These annual plants occur on serpentine soils in disjunct populations in the Coast Ranges of California from Tehama County to San Luis Obispo County, isolated by intervening regions of unsuitable, non-serpentine habitat. this isolation, accompanied by inbreeding, may have resulted in the many different phenotypes identifiable among populations within each species. The phylogeny of the group is unknown and taxonomic delimitations are disputed: from three varieties of one species to 13 distinct species have been recognized. Thus, the S. glandulosus complex not only requires systematic study but it also offers an excellent forum in which to study speciation processes in serpentine endemics. Based on interpopulational crossing experiments, Kruckeberg (1957) showed a negative correlation between interfertility of populations of the complex and the distance by which they were separated. We propose to build on Kruckeberg's classic studies of isolation by distance using a combination of enzyme electrophoresis and restriction site analysis of chloroplast DNA to examine genetic divergence, systematic relationships, and evolutionary processes. The specific objectives are : (1) assess allozymic and cpDNA divergence among populations and correlate genetic divergence with geographic patterns; (2) construct a phylogeny of the complex using cpDNA restriction site data and use the phylogeny to evaluate putative examples of paleoendemism and neoendemism, recent derivation of restricted taxa from more widespread ones, and recurrent adaptation of serpentine tolerance; (3) estimate levels of interpopulational gene flow using allozymic data; and (4) compare levels of allozyme variability in restricted and widespread taxa. The integration of interfertility, allozymic, and restriction site analyses of the S. glandulosus complex offers an almost unparalleled venus from which to study speciation processes, and will provide the information necessary for sound management of the complex.