Dissertation Research: Dispersed Introgression Between Yucca baccata and Y. schidigera (Agavaceae)

长期以来，杂交对于植物育种和作物生产一直很重要。然而，杂交在野生植物进化中的重要性却不太为人所知。这部分是因为难以检测和记录杂交事件的发生，也难以区分从另一物种引入的遗传新奇性与通过突变过程在物种内产生的自然遗传变异。最近，直接分析植物DNA的新的和强大的分子方法使得对这个问题的广泛分析成为可能。研究生汉森在兰乔圣安娜植物园的洛伦·里斯伯格博士的指导下，正在研究美国西南部两种丝兰之间重复杂交事件（称为基因渗入）的假定案例。蛋白质标记物通过电泳进行分析，核核糖体和质体DNA的变异通过酶限制位点进行分析。还正在研究几个相关的丝兰物种，以推断该组中物种之间的系统发育关系，以确定这两个杂交物种是否有一个最近的共同祖先。最近的祖先也可能导致共享遗传标记的模式，这可能与杂交混淆。蛋白质和DNA标记的范围进行研究，从核和叶绿体基因组，将有助于区分最近的共同祖先和目前的渐渗。因此，这项研究将促进对自然植物种群杂交的理解，并将有助于培养年轻的植物科学家。

Hybridization has long been important to plant breeding and the production of crop plants. Less well understood, however, is the importance of hybridization in the evolution of wild plants. In part this is because it can be difficult to detect and document the occurrence of hybridization events and to distinguish genetic novelties introduced from another species from natural genetic variation arising within a species by mutation processes. Recently, new and powerful molecular methods for analyzing directly the DNA of plants have made possible a broad analysis of this problem. Graduate student Hanson under the guidance of Dr. Loren Rieseberg of the Rancho Santa Ana Botanic Garden is studying a presumptive case of repeated hybridization events (termed introgression) between two species of yuccas of the American Southwest. Protein markers are being assayed by electrophoresis, and variation in nuclear ribosomal and plastid DNA is being analyzed by enzymatic restriction-sites. Several related yucca species are also being studied to infer the phylogenetic relationships among species in this group, in order to determine whether the two hybridizing species have shared a recent common ancestor. Recent ancestry can also lead to a pattern of shared genetic markers that could be confused with hybridization. The range of protein and DNA markers to be studied, from both nuclear and chloroplast genomes, will help distinguish between recent common ancestry and current introgression. The study will thus advance understanding of hybridization in natural plant populations, and will help in the training of a young plant scientist.