Data from: Analyzing reticulate relationships using CpDNA and pyrosequenced ITS1 as exemplified by Veronica subgen. Pseudolysimachium (Plantaginaceae)

Veronica subgen. Pseudolysimachium constitutes a group of about 28 species across northern Eurasia, many of them with considerable intraspecific morphological variation. This intraspecific variation may be due to large geographical distribution area, wide ecological amplitude, or widespread hybridization and polyploidization. Several recent studies using molecular data have shown that hybridization as an explanation for generating evolutionary novelties and high intraspecific variation may be more common than previously thought. Here we investigate the importance of hybridization in generating morphological variation and blurring species boundaries in V. subgen. Pseudolysimachium using analyses of cpDNA sequences from 139 individuals from 18 species and ten putative hybrids, and pyrosequenced ITS1 nrDNA sequences from 37 individuals from 16 species and four putative hybrids. In addition, we estimated ploidy levels for 42 individuals of ten species and five putative hybrids using flow cytometry. Analyses of cpDNA did not resolve phylogenetic structure (most of the species were polyphyletic). Our second approach, pyrosequencing of ITS1, generated up to nine different unique sequences per individual and phylogenetic analyses of the dataset resolved some basal nodes but, again, species were often non-monophyletic. The results are most compatible with a scenario of an East Asian origin and repeated spread across Pleistocene Eurasian steppes, known as important plant diversification center, with frequent interspecific hybridization. We compare the applicability of these molecular regions for resolving hybridizing species complexes and specifically address hypotheses of hybrid origins for several species within the subgenus. However, any population genetic, phylogeographic or other analysis of evolutionary questions in one species alone would be futile without considering introgression from related species.

婆婆纳属假穗花亚属（Veronica subgen. Pseudolysimachium）是一类分布于欧亚大陆北部的植物类群，包含约28个物种，其中多数类群存在显著的种内形态变异。这种种内变异可能源于其广阔的地理分布范围、宽泛的生态幅，或是广泛的杂交与多倍化事件。近期多项基于分子数据的研究表明，杂交作为产生演化新特征与高程度种内变异的诱因，其普遍性可能远超此前的认知。本研究针对该亚属，探讨杂交在驱动形态变异、模糊物种界限中的核心作用：研究共获取了18个物种及10个推定杂种的139份个体的叶绿体DNA（cpDNA）序列，以及16个物种与4个推定杂种的37份个体的焦磷酸测序核核糖体DNA ITS1区（ITS1 nrDNA）序列；此外，本研究借助流式细胞术对10个物种及5个推定杂种的42份个体进行了倍性水平估算。叶绿体DNA分析未能解析出清晰的系统发育结构，多数物种呈现多系演化特征。第二种分析方法——焦磷酸测序核核糖体DNA ITS1区（ITS1 nrDNA）——在单一个体中最多可检测到9种不同的独特序列；对该数据集的系统发育分析虽解析出部分基部节点，但物种仍多呈非单系演化状态。研究结果最支持如下演化场景：该亚属起源于东亚，随后反复扩散至更新世时期的欧亚草原——该区域为重要的植物多样化中心——且其间频繁发生种间杂交事件。本研究对比了这些分子区域在解析杂交物种种复合体时的适用性，并专门验证了该亚属内多个物种的杂交起源假说。然而，若不考虑来自近缘物种的基因渐渗，仅针对单一物种开展种群遗传学、谱系地理学或其他演化相关研究，将毫无学术价值。