Dissertation Research: Inflorescence Size in Natural and Experimental Populations of Milkweeds

一个主要的争议是关于大型花展示对低坐果植物的适应性意义：为什么产生这么多额外的花是为了产生花粉，从而成功地将雄性基因传递给其他花。这种“花粉捐赠假说”一直是一个难以解决的问题。虽然测量果实或种子的产量相当容易，但从技术上讲，量化花粉的成功要困难得多。最近，植物种群生物学家已经转向父系排除分析作为一个可能的解决方案。原则上，这项技术与使用血型来确定人类亲子关系的过程相同。本研究将在乳草（Asclepias）中验证花粉捐赠假说。遗传标记从蛋白质电泳将用于执行父系排除分析。这将识别种群中单个植物产生的种子。通过去除实验群体中的花来控制花序大小，以确定花序大小与种子数量和产生的种子数量之间的关系。这项研究将提供重要的基本信息，关于塑造植物花序大小进化的力量。它还将提供有关种群内部和种群之间基因流动水平的数据。最后，植物父系分析的发展将为研究本地和作物植物的育种系统提供基础。此外，如果需要再次使用乳草作为木棉和橡胶的替代来源（就像第二次世界大战那样），我们将更好地了解限制坐果的力量，并将对如何设计有效的育种计划有新的见解。

A major controversy exists regarding the adaptive significance of large floral displays in plants with consistently low fruit-set: why produce so many the extra flowers are there to produce pollen which will successfully convey male genes to other flowers. This "pollen donation hypothesis" has been a difficult issue to address. While it is reasonably easy to measure fruit or seed production, it is technically much more difficult to quantify pollen success. Recently, plant population biologists have turned to paternity exclusion analysis as a possible solution to the problem. In principle, the technique is identical to the process of using blood types to determine human paternity. The proposed research will test the pollen donation hypothesis in milkweeds (Asclepias). Genetic markers from protein electrophoresis will be used to perform a paternity exclusion analysis. This will identify seeds sired by individual plants in the population. Inflorescence size will be manipulated by removing flowers in experimental populations to determine the relationship between inflorescence size and numbers of seeds sired and numbers of seeds produced. This study will yield important basic information about the forces that shape the evolution of inflorescence size in plants. It will also provide data regarding levels of gene flow within and between populations. Finally the development of paternity analysis in plants will provide a basis for investigating breeding systems of both native and crop plants. Furthermore, should the need arise again (as in World War II) for milkweeds to be used as substitute sources of kapok and rubber, we will understand better the forces that limit fruit-set and will have new insights into how to design effective breeding programs.