An expanded molecular phylogeny of Plumbaginaceae, with emphasis on Limonium (sea lavenders): taxonomic implications and biogeographic considerations

Plumbaginaceae is characterized by a history of multiple taxonomic rearrangements and lacks a broad molecular phylogenetic framework. Limonium is the most species‐rich genus of the family with ca. 600 species and cosmopolitan distribution. Its center of diversity is the Mediterranean region, where ca. 70% of all Limonium species are endemic. In this study, we sample 201 Limonium species covering all described infrageneric entities and spanning its wide geographic range, along with 64 species of other Plumbaginaceae genera, representing 23 out of 29 genera of the family. Additionally, 20 species of the sister family Polygonaceae were used as outgroup. Sequences of three chloroplast (trnL‐F, matK, and rbcL) and one nuclear (ITS) loci were used to infer the molecular phylogeny employing maximum likelihood and Bayesian analyses. According to our results, within Plumbaginoideae, Plumbago forms a non‐monophyletic assemblage, with Plumbago europaea sister to Plumbagella, while the other Plumbago species form a clade sister to Dyerophytum. Within Limonioideae, Ikonnikovia is nested in Goniolimon, rejecting its former segregation as genus distinct from Goniolimon. Limonium is divided into two major clades: Limonium subg. Pteroclados s.l., including L. sect. Pteroclados and L. anthericoides, and L. subg. Limonium. The latter is divided into three well‐supported subclades: the monospecific L. sect. Limoniodendron sister to a clade comprising a mostly non‐Mediterranean subclade and a Mediterranean subclade. Our results set the foundation for taxonomic proposals on sections and subsections of Limonium, namely: (a) the newly described L. sect. Tenuiramosum, created to assign L. anthericoides at the sectional rank; (b) the more restricted circumscriptions of L. sect. Limonium (= L. sect. Limonium subsect. Genuinae) and L. sect. Sarcophyllum (for the Sudano‐Zambezian/Saharo‐Arabian clade); (c) the more expanded circumscription of L. sect. Nephrophyllum (including species of the L. bellidifolium complex); and (d) the new combinations for L. sect. Pruinosum and L. sect. Pteroclados subsect. Odontolepideae and subsect. Nobiles.

白花丹科（Plumbaginaceae）以历经多次分类学修订为典型特征，且尚未建立统一的广谱分子系统发育框架。补血草属（Limonium）是该科物种最丰富的属，约含600个物种，呈广布分布。其多样性中心位于地中海地区，该区域内约70%的补血草属物种为特有种。本研究共采样201个补血草属物种，涵盖所有已描述的属下类群，覆盖其广泛的地理分布范围；同时采样了白花丹科其他属的64个物种，涵盖该科29个属中的23个属。此外，选取姊妹科蓼科（Polygonaceae）的20个物种作为外类群（outgroup）。本研究选取3个叶绿体（chloroplast）基因座（trnL-F、matK与rbcL）及1个核基因座（ITS）的序列，采用最大似然法与贝叶斯分析进行分子系统发育推断。研究结果显示，在白花丹亚科（Plumbaginoideae）中，白花丹属（Plumbago）构成非单系群：欧洲白花丹（Plumbago europaea）与蓝花丹属（Plumbagella）互为姊妹群，而其余白花丹属物种构成的支系与匙叶草属（Dyerophytum）互为姊妹群。在补血草亚科（Limonioideae）中，冰花丹属（Ikonnikovia）嵌套于驼舌草属（Goniolimon）内，推翻了此前将其独立为属的分类处理。补血草属可分为两个主要支系：广义翼枝补血草亚属（Limonium subg. Pteroclados s.l.），包含翼枝补血草组（L. sect. Pteroclados）与花药叶补血草（L. anthericoides）；另一支为补血草亚属（Limonium subg. Limonium）。后者可分为三个支持度良好的亚支：单种的树状补血草组（L. sect. Limoniodendron），与一个由主要非地中海亚支和地中海亚支构成的支系互为姊妹群。本研究结果为补血草属组及亚组的分类修订奠定了基础，具体包括：（a）新建立细枝补血草组（"L. sect. Tenuiramosum"），以将花药叶补血草（L. anthericoides）归入该组等级；（b）对补血草组（"L. sect. Limonium"，等价于"L. sect. Limonium subsect. Genuinae"）与肉叶补血草组（"L. sect. Sarcophyllum"，对应苏丹-赞比西/撒哈拉-阿拉伯支系）进行更为严格的界定；（c）扩大肾叶补血草组（"L. sect. Nephrophyllum"）的分类范围，将雏菊叶类群（"L. bellidifolium complex"）的物种纳入其中；（d）为粉霜补血草组（"L. sect. Pruinosum"）、翼枝补血草组下的齿鳞亚组（"L. sect. Pteroclados subsect. Odontolepideae"）及高贵亚组（"L. sect. Pteroclados subsect. Nobiles"）提供新组合。