Phylogenetic relationships among Old World Ruellia L.: a new classification and reinstatement of the genus Dinteracanthus Schinz

The genus Ruellia (Acanthaceae) consists of some ca. 350 species that are concentrated in tropical and subtropical regions of the world. Old World Ruellia have never been the focus of explicit phylogenetic study, yet comprise the earliest diverging lineages in the genus and contain upwards of 100 species. We sampled 52 accessions representing 29 OW species of Ruellia for phylogenetic analysis. Results yielded five clades that were strongly supported and marked by morphological synapomorphies. Analyses additionally recovered a newly recognized lineage within the tribe Ruellieae, a small radiation of plants in the deserts of Namibia and Angola, and the name Dinteracanthus is available for reinstatement. Divergence time analysis using a primary fossil calibration revealed relatively young estimates for crown ages of all five clades of OW Ruellia (2.5 Ma ‐ 630,000 ypb) as well as for Dinteracanthus (2.0 Ma). Ancestral state reconstruction of pollination systems among OW Ruellia suggest a minimum of two transitions from short-tongued insect pollination to nocturnal moth pollination, one from short-tongued insect to bird pollination, and one reversal from nocturnal moth pollination back to short-tongued insect pollination. We formally delimit the five clades of OW Ruellia as sections and present a key to aid in their identification: sect. Eusiphon, sect. Dipteracanthus, sect. Madagasikara, sect. Pseudoruellia, and sect. Discifolia. We provisionally treat 77 of 97 species of OW Ruellia among these five sections, with the remaining names considered to be unresolved.

爵床属（Ruellia，爵床科Acanthaceae）约包含350个物种，集中分布于全球热带及亚热带区域。旧世界爵床类群从未成为专门系统发育研究的对象，但其构成了该属最早分化的谱系，且物种数量逾100个。本研究采样了代表旧世界29个爵床物种的52份种质材料用于系统发育分析，结果得到5个高支持率的演化支，且这些支系均具有形态共衍征。分析还在爵床族（Ruellieae）中发现了一个新确认的演化支谱系，该类群为纳米比亚与安哥拉沙漠中的小型辐射演化植物，丁特棘爵属（Dinteracanthus）的名称可被恢复使用。采用主化石校准开展的分化时间分析显示，旧世界爵床属全部5个演化支的冠群年龄估算值均相对较新（250万年至63万年前），丁特棘爵属的冠群年龄也为200万年。对旧世界爵床类群传粉系统的祖先状态重建结果表明，其传粉系统至少经历了两次从短舌昆虫传粉向夜行性蛾类传粉的转变、一次从短舌昆虫传粉向鸟类传粉的转变，以及一次从夜行性蛾类传粉逆转回短舌昆虫传粉的事件。本研究正式将旧世界爵床属的5个演化支界定为组，并发布了用于其物种鉴定的检索表：Eusiphon组（sect. Eusiphon）、Dipteracanthus组（sect. Dipteracanthus）、Madagasikara组（sect. Madagasikara）、Pseudoruellia组（sect. Pseudoruellia）以及Discifolia组（sect. Discifolia）。本研究暂定将97个旧世界爵床物种中的77个归入上述5个组，剩余物种名称暂视为分类学存疑类群。