Data from: Resolving phylogenetic relationships of the recently radiated carnivorous plant genus Sarracenia using target enrichment

The North American carnivorous pitcher plant genus Sarracenia (Sarraceniaceae) is a relatively young clade (<3 million years ago) displaying a wide range of morphological diversity in complex trapping structures. This recently radiated group is a promising system to examine the structural evolution and diversification of carnivorous plants; however, little is known regarding evolutionary relationships within the genus. Previous attempts at resolving the phylogeny have been unsuccessful, most likely due to few parsimony-informative sites compounded by incomplete lineage sorting. Here, we applied a target enrichment approach using multiple accessions to assess the relationships of Sarracenia species. This resulted in 199 nuclear genes from 75 accessions covering the putative 8–11 species and 8 subspecies/varieties. In addition, we recovered 42 kb of plastome sequence from each accession to estimate a cpDNA-derived phylogeny. Unsurprisingly, the cpDNA had few parsimony-informative sites (0.5%) and provided little information on species relationships. In contrast, use of the targeted nuclear loci in concatenation and coalescent frameworks elucidated many relationships within Sarracenia even with high heterogeneity among gene trees. Results were largely consistent for both concatenation and coalescent approaches. The only major disagreement was with the placement of the purpurea complex. Moreover, results suggest an Appalachian massif biogeographic origin of the genus. Overall, this study highlights the utility of target enrichment using multiple accessions to resolve relationships in recently radiated taxa.

瓶子草属（Sarracenia）是北美食肉猪笼草类群，隶属于瓶子草科（Sarraceniaceae），是一个相对年轻的演化支（clade，起源距今不足300万年），其复杂的捕虫结构展现出丰富的形态多样性。这一新近辐射演化的类群是研究食肉植物结构演化与物种分化的极具潜力的研究体系；但目前学界对该属内的演化关系仍知之甚少。此前针对该属系统发育解析的研究均未取得成功，其核心诱因极有可能为简约信息位点（parsimony-informative sites）匮乏，叠加不完全谱系分选（incomplete lineage sorting）的干扰。本研究采用靶向富集（target enrichment）技术，并结合多份样本材料，对瓶子草属物种的演化关系展开评估。最终从覆盖该属推定的8至11个物种与8个亚种/变种的75份样本中，获得了199个核基因序列。此外，本研究还从每份样本中获得了42 kb的质体基因组（plastome）序列，以此构建基于cpDNA（叶绿体DNA）的系统发育树。不出所料，cpDNA的简约信息位点占比仅为0.5%，几乎无法为物种间的演化关系提供有效依据。与之形成鲜明对比的是，即便基因树间存在较高异质性，通过串联法（concatenation）与溯祖框架（coalescent frameworks）分析靶向核基因位点，仍得以阐明瓶子草属内的诸多演化关系。两种分析方法的结果整体保持一致，仅在紫瓶子草复合体（purpurea complex）的系统位置上存在显著分歧。此外，研究结果还表明该属的生物地理起源地为阿巴拉契亚地块（Appalachian massif）。综上，本研究证实，结合多份样本的靶向富集技术可有效解决新近辐射演化类群的系统发育关系解析难题。