Dissertation Research: An Evolutionary Study of Astragalus Sect. Leptocarpi Subsect. Californici (Fabaceae)

黄芪是世界上最大的开花植物属，在北美西部特别有代表性，那里有400多种。然而，其物种很少成为生物系统研究的主题。原产于亚利桑那州、加利福尼亚州和内华达州的九种密切相关的一年生成员被选为进行此类研究的合适群体。这些植物的果实和花在形态上的差异程度，反映在它们以前被划分为三个不同的属上，是相当显著的。拟议研究的目的是研究产生和保存这种多样性的进化过程。具体而言，本研究将1)基于解剖学、细胞学和遗传学数据阐明研究组成员之间的系统发育关系；2)利用遗传变异分析得出的数据来评估该群体的育种系统、物种形成过程和分化水平。

Astragalus (loco weed) is the largest genus of flowering plants in the world and is especially well represented in western North America, where there are over 400 species. Nevertheless, its species have rarely been the subject of a biosystematic study. Nine closely related annual members of the genus, native to Arizona, California, and Nevada, have been chosen as an appropriate group for such a study. The extent of morphological divergence in the fruits and flowers of these plants, reflected in their previous assignment to three different genera, is quite remarkable. The objective of the proposed research is to examine the evolutionary processes which have brought about and preserved this diversity. Specifically, this study will 1) clarify phylogenetic relationships among the members of the study group based on anatomical, cytological, and genetic data, and 2) use data derived from the analysis of genetic variation to evaluate breeding systems, speciation processes, and levels of divergence in the group.