Dissertation Research: The Role of Hybridization in the Evolution of Argyranthemum in Macaronesia

9902276詹森和格尔岑海洋岛屿是研究进化过程的理想天然实验室。 自达尔文以来，它们的孤立性、环境的多变性和容易确定的年龄帮助生物学家解开了进化变化背后的力量。 自然杂交是动植物进化的一种潜在的主要力量，通过对夏威夷和胡安费尔南德斯群岛物种的研究，我们对自然杂交的理解有了很大的进步。在罗伯特·K博士的指导下，德克萨斯大学奥斯汀分校的研究生Leslie Goertzen正在研究杂交在植物属（菊科）进化中的作用。这组24个物种只在Macaronesian群岛（加那利群岛，马德拉群岛和萨尔瓦多群岛）发现，是整个岛屿海拔地区适应辐射的一个壮观的例子，具有许多特征，使其成为解决进化问题的模型系统。 本研究将探讨古渐渗的属，以及当代物种接触的动态和后果的证据。这些岛屿植物的系统发育框架将使用可变的核DNA序列构建，这些数据和母系遗传的叶绿体DNA之间的统计比较将进行。 初步数据表明，几个物种对的两个数据集之间存在显着不一致，这增加了这些谱系进化过程中渐渗杂交的可能性。 当代杂交的具体情况将通过筛选自然种群和杂交种群的种特异性核和叶绿体遗传标记来检查。这将允许种间基因流动的方向和程度，如果有的话，被确定。来自不同海拔地区的物种的潜在杂交种特别令人感兴趣，以了解导致迁移到新栖息地的因素。此外，这些分析将提供与几种稀有物种的保护工作相关的数据，并有助于理解一个理论过程，该过程威胁着许多孤立条件下的生物，通过杂交灭绝。

9902276Jansen and Goertzen Oceanic islands are ideal natural laboratories for studying evolutionary processes. Their isolation, environmental variability, and easily determined ages have aided biologists ever since Darwin in unraveling the forces behind evolutionary change. Our understanding of natural hybridization, a potentially major force in plant and animal evolution, has been advanced considerably by studies of species in the Hawaiian and Juan Fernandez islands in particular. Under the direction of Dr. Robert K. Jansen at the University of Texas at Austin, graduate student Leslie Goertzen is studying the role of hybridization in the evolution of the plant genus Argyranthemum (family Asteraceae). This group of 24 species found only in the Macaronesian archipelagos (Canaries, Madeira, and Salvage islands) is a spectacular example of adaptive radiation throughout the islands' elevational zones and has many characteristics which make it a model system for addressing evolutionary questions. This study will examine evidence for ancient introgression in the genus as well as the dynamics and consequences of contemporary species contact. A phylogenetic framework for these island plants will be constructed using variable nuclear DNA sequences, and a statistical comparison between these data and maternally inherited chloroplast DNA will be performed. Preliminary data suggest significant incongruence between the two data sets for several species pairs, raising the possibility of introgressive hybridization during the evolution of these lineages. Specific cases of contemporary hybridization will be examined by screeningnatural and hybrid populations for species-specific nuclear and chloroplast genetic markers. This will allow the direction and extent of interspecific gene flow, if any, to be determined. Potential hybrids of species from different elevational zones are of special interest, for understanding factors causing shifts into new habitats. In addition, the analyses will provide data of relevance to conservation efforts for several rare species and contribute to the understanding of a theoretical process which threatens many organisms in isolated conditions, extinction via hybridization.