A Continental-Wide Perspective: The Genepool of Nuclear Encoded Ribosomal DNA and Single-Copy Gene Sequences in North American Boechera (Brassicaceae)

74 of the currently accepted 111 taxa of the North American genus Boechera (Brassicaceae) were subject to pyhlogenetic reconstruction and network analysis. The dataset comprised 911 accessions for which ITS sequences were analyzed. Phylogenetic analyses yielded largely unresolved trees. Together with the network analysis confirming this result this can be interpreted as an indication for multiple, independent, and rapid diversification events. Network analyses were superimposed with datasets describing i) geographical distribution, ii) taxonomy, iii) reproductive mode, and iv) distribution history based on phylogeographic evidence. Our results provide first direct evidence for enormous reticulate evolution in the entire genus and give further insights into the evolutionary history of this complex genus on a continental scale. In addition two novel single-copy gene markers, orthologues of the Arabidopsis thaliana genes At2g25920 and At3g18900, were analyzed for subsets of taxa and confirmed the findings obtained through the ITS data.当前学界认可的北美十字花科（Brassicaceae）弯蕊芥属（Boechera）111个分类单元（taxa）中，有74个被纳入系统发育重建与网络分析。本数据集涵盖911份种质样品（accessions），其对应的内转录间隔区（ITS，Internal Transcribed Spacer）序列已完成分析。系统发育分析得到的多数系统发育树分辨率不佳，结合验证该结果的网络分析结果，这一现象可被解读为该类群存在多次独立且快速物种分化事件的指示信号。本次网络分析叠加了四类辅助数据集：i）地理分布数据、ii）分类学数据、iii）繁殖模式数据、iv）基于系统地理学证据的类群分布历史数据集。本研究首次为整个弯蕊芥属存在广泛的网状演化提供了直接证据，并为这一复杂类群在大陆尺度上的演化历史提供了新的深入见解。此外，研究人员针对部分分类单元分析了两个全新的单拷贝基因标记——拟南芥（Arabidopsis thaliana）基因At2g25920与At3g18900的直向同源基因（orthologues），并验证了通过内转录间隔区序列数据得到的研究结果。