Evolution in the genus Baccharis L. - analysis of a homoploid hybrid complex based on genomic and chemical diversity

杂交被认为在生物进化中起着重要作用，特别是在植物中。虽然在大多数情况下杂种不育性通过多倍化克服，但也有植物物种组保持在亲本物种的倍性水平的例子。这使得杂种与一个或两个亲本回交，最终形成密集的杂种群。这种同倍体杂种复合体的一个例子是Baccharis L.（菊科）在智利，包括16种万年青灌木是雌雄异株和昆虫授粉。这些植物含有多种化学化合物，包括具有生物活性的萜烯和黄酮类化合物，例如用于防御食草动物或病原体。这一组的分类学已被彻底调查，导致许多杂交类群相互连接的描述假定纯种。然而，分类群之间的系统发育关系仍然没有得到解决，杂交事件的基础上假设的形态alone.Technical和方法的进步，在过去的几年里开辟了新的可能性，解开复杂的结构和演化的混合复杂的Baccharis一样。在这个项目中，我们将应用下一代测序技术，使用从整个植物基因组中采样的累积序列信息来重建涉及一组Baccharis杂交物种在智利自然栖息地的进化历史。将在过去气候变化的背景下讨论进化变化，并考虑过去几个世纪人类对植被的改造。为了了解化学变体的适应价值，我们将研究Baccharis杂交种的特化代谢。特别是，我们将分析挥发性化合物和非挥发性的极性代谢物在混合群，以阐明杂交如何影响专门的化合物的组成。适合杂交的后果将在原位和在耶拿的实验种群中进行研究，我们也将进行喂养实验。该项目汇集了来自马克斯·普朗克化学生态学研究所和耶拿弗里德里希·席勒大学的两个工作组，他们在植物专门代谢，经典分类学，分子生物学和分子群体遗传学的生态和进化方面的研究方面具有专业知识。

Hybridization has been considered to play an important role in biological evolution, especially in plants. While in most cases hybrid sterility is overcome by polyploidization, there are also examples for plant species groups that remain at the ploidy level of the parental species. This enables the hybrids to backcross with one or both parents eventually forming dense hybrid swarms. An example of such a homoploid hybrid complex is the genus Baccharis L. (Asteraceae) in Chile, comprising 16 species of evergreen shrubs which are dioecious and insect-pollinated. The plants contain a multitude of chemical compounds including terpenes and flavonoids that are biologically active, for example in defense against herbivores or pathogens. The taxonomy of this group has been investigated thoroughly leading to the description of numerous hybrid taxa interconnecting supposedly pure species. However, phylogenetic relationships between the taxa remain unresolved and hybridization events are hypothesized on the base of morphology alone.Technical and methodological advances over the last years have opened up new possibilities to disentangle the intricate structure and evolution of hybrid complexes like Baccharis. In this project we will apply next generation sequencing techniques using accumulated sequence information sampled from the whole plant genome to reconstruct the evolutionary history involving a group of hybridizing species in Baccharis in their natural habitats in Chile. Evolutionary changes will be discussed in the context of climate change in the past and considering vegetation transformation by humans during the last centuries. In order to understand the adaptive value of chemical variants, we will investigate the specialized metabolism of Baccharis hybrids. In particular we will analyze volatile compounds and non-volatile polar metabolites in hybrid swarms to elucidate how hybridization affects the composition of specialized compounds. Fitness consequences of hybridization will be studied in situ and in an experimental population at Jena where we also will perform feeding experiments. The project brings together two working groups from the Max Planck Institute for Chemical Ecology and the Friedrich Schiller University of Jena with expertise in investigations on ecological and evolutionary aspects of plant specialized metabolism, classical taxonomy, molecular phylogeny, and molecular population genetics.