Dissertation Research: Evolutionary History of Reproductive Systems in Closely Related Taxa of the Lichen-forming Genus Porpidia (Ascomycota)

本研究项目的总体目标是阐明Porpidia属（地衣形成的子囊菌门）内的关系，并分析其种内和种间生殖模式转换的分布和相互依赖性。之所以选择这一属，是因为它聚集了许多表现出截然不同的生殖模式的密切相关的分类群。P. flavocoerulescens（有性）/P。选取无性“种对”Melinodes进行详细的种群水平分析。两种繁殖模式之间的假设变化模式将使用系统发育方法进行检验。“物种对”内的潜在种群结构和历史将使用综合系统地理学和谱系学分析进行研究。今天，尽管这个问题在理论上得到了深入的关注，但有性和无性生殖模式的意义及其持续共存仍然没有得到解决。造成这种情况的部分原因是现有经验数据的稀缺性和差异性，因此无法对提出的假设进行严格的检验。像Porpidia这样的模型系统包含了从有性到无性的不同繁殖模式的密切相关物种，为深入了解不同水平重组的历史和后果提供了重要手段。到目前为止，调查几乎完全集中在该问题的系统发育或种群遗传方面。本研究将是首次在地衣子囊菌中整合系统发育和群体遗传学方法。它不仅可以推断进化史的模式，还可以深入了解潜在的人口过程和形成这些模式的历史事件。

0105024MuellerThe overall objectives of this research project are to clarify relationships within the genus Porpidia (lichen-forming Ascomycota), and to analyze the distribution and interdependence of transitions between reproductive modes within and among its species. The genus was chosen, due to its accumulation of closely related taxa that show contrasting reproductive modes. The P. flavocoerulescens (sexual)/P. melinodes (asexual) "species pair" was selected for detailed population-level analyses. Hypothetical patterns of changes between the two modes of reproduction will be tested using a phylogenetic approach. The underlying population structure and history within the "species pair" will be studied using an integrated phylogeographic and genealogical analysis.Today the significance of sexual and asexual reproductive modes and their continued coexistence are still unsolved, despite the in-depth theoretical attention the issue has received. This situation is in part due to the scarcity and disparate nature of available empirical data, which do not allow stringent tests of proposed hypotheses. Model systems such as Porpidia that include closely related species with different modes of reproduction ranging from sexual to asexual provide important means to gain insight into the history and consequences of different levels of recombination. So far, investigations have concentrated almost exclusively on either the phylogenetic or population-genetic aspects of the problem. The present study will be the first in lichenized ascomycetes to integrate both phylogenetic and population-genetic approaches. It will not only infer patterns of evolutionary history, but also provide insight into the underlying population processes and historical events shaping these patterns.