Hybridization and reticulation as driving forces in the evolution of grasses from temperate regions (grass subfamily Pooideae)?

草亚科(约3300种)是地球上S温带气候带的特征。这个植物群对人类来说非常有意义，因为它进化出了小麦、大麦、黑麦和燕麦等主要农作物。因此，重要的是(1)确定这个亚家族中存在的进化谱系，(2)澄清它们之间的相互关系，(3)确定它们如何起源的时间序列。在前一个项目阶段，我们实现了来自叶绿体和核基因组(matK-trnK区，重复的核核糖体ITS)的DNA序列数据的密集属的覆盖。结合形态、染色体和生物地理研究结果对数据进行了分析。这导致了几个深远的分类学变化，包括在Pooideae的早期分歧谱系中发现了新的部落Duthieeae，改变了主要进化谱系(部落、亚族)的范围和重新安排。总体而言，Pooideae亚科部分成员的分子系统发育信息以及许多属在树中的位置似乎与基于形态的分类不一致。因此，过去频繁的杂交，部分甚至是来自不同部落的属之间的杂交(部落间杂交)被讨论为这些不一致的潜在解释。为了获得过去杂交和网状进化作用的直接证据，该项目将重点放在双亲遗传的核基因组上。近年来，核单拷贝基因被越来越多地用于分析杂交过程、同倍体的导入、二倍体-多倍体的关系，从而最终进化成网状结构。这些非重复标记经常比核糖体阵列更好地保存进化历史，因为它们不太容易发生基因转换，在这个过程中，一个父母拷贝被另一个取代。在我们关于拓扑异构酶6(TopO6)和乙酰辅酶A羧化酶1(Acc1)的初步工作的基础上，我们将对这些SCG的5个外显子/内含子区域进行测序，这些外显子/内含子区域已经在我们之前的研究中被成功地测试，以及来自其他SCG的4个外显子/内含子区域的测序。我们将集中讨论Pooideae(Stipeae，Duthieeae等部落)中广泛未解决的早期分歧谱系。和大型燕麦/坡族部落复合体。在我们的研究中，从这些类群中选择了70个和190个具有代表性的分类群。将使用传统的桑格方法和下一代测序(NGS)来收集DNA信息。SCGs的数据集将与已经为分类学上完全重叠的分类群样本生成的叶绿体matK-trnK和核ITS数据进行比较。这种对不同遗传(单亲和双亲)和不同进化的DNA区域的分析有望首次提供基于DNA的杂交过程的直接证据，并在它们的重建中具有很高的潜力。

The grass subfamily Pooideae (~3300 species) is characteristic of the Earth´s temperate climate zones. This plant group is extremely meaningful for humans, because it has evolved major crop plants like wheat, barley, rye and oat. It is significant therefore (1) to identify the evolutionary lineages present within this subfamily, (2) to clarify their interrelations and (3) to determine the temporal sequence how they originated. In the preceding project phase we achieved a dense coverage of genera for DNA sequence data from the plastid and nuclear genome (matK-trnK region, repetitive nuclear ribosomal ITS). The data were analysed in conjunction with morphological, chromosomal and biogeographical research results. This led to several far-reaching taxonomic changes including the discovery of the new tribe Duthieeae among the early diverging lineages of Pooideae, to altered circumscriptions and re-arrangements of major evolutionary lineages (tribes, subtribes). On the whole, the molecular phylogenetic information for parts of the subfamily Pooideae and the placement of many genera in the trees seem to be at odds with classifications based on morphology. Frequent past hybridisation, partly even between genera from different tribes (intertribe hybridisation) therefore was discussed as a potential explanation of these inconsistencies. To obtain direct evidence on the role of past hybridisation and reticulate evolution, this project will focus on the biparentally inherited nuclear genome. Nuclear single copy genes (SCGs) have been increasingly used in recent years to analyse hybrid processes, introgression in homoploids, diploid-polyploid relationships, thus finally evolutionary reticulation. These non-repetitive markers preserve the evolutionary history frequently much better than the ribosomal arrays since they are less prone to gene conversion, a process, in which one parental copy is replaced by the other. Building on our preliminary work on topoisomerase 6 (Topo6) and acetyl-CoA carboxylase 1 (Acc1), we will sequence 5 exon/intron regions of these SCGs, which already have been successfully tested in our previous studies, and 4 from other SCGs. We will focus on the widely unresolved early diverging lineages of Pooideae (tribes Stipeae, Duthieeae, etc.) and the large Aveneae/Poeae tribe complex. For our study, 70 and 190 representative taxa have been selected from these groups. Conventional Sanger method and Next Generation Sequencing (NGS) will be used to gather DNA information. The data set of the SCGs will be compared with the plastid matK-trnK and nuclear ITS data, which have already been generated for the taxonomically completely overlapping sample of taxa. This analysis of differently inherited (uniparentally vs. biparentally) and differently evolving DNA regions is expected to give for the first time direct, DNA-based evidence of hybrid processes and has a high potential in their reconstruction.