Revised delimitation of Croton campestris (Euphorbiaceae), including description of two new species, molecular phylogenetic, anatomical and micromorphological data

ABSTRACT Croton section Adenophylli is the largest section in the genus, with around 223 species distributed in the neotropical region. One of the main diagnostic characteristics of this section is the fruit columella, which has three prominent ascending terminal appendages. During a taxonomic review of this section in Brazil, we observed that C. campestris has a problematic taxonomic circumscription, thereby being confused with some other congeners. We investigate the circumscription of C. campestris through the examination of several herbarium specimens across its entire geographic range, and in its different habitats. We conducted macro- and micro-morphological studies as well as molecular analyses based on DNA sequences. Our results allow us to propose two new species (C. hatschbachii and C. stellatorotatus), update the nomenclature of C. campestris and C. subvillosus, and define the systematic positions, phylogenetic relationships, morphology and leaf anatomy of the above-mentioned taxa. The species are described, and their geographic distributions, morphological relationships, flowering and fruiting times, and conservation statuses are commented on. The two new species are also illustrated. Seventeen new synonyms, thirteen lectotypes and two neotypes are proposed. We also provide a key for the identification of 11 taxa belonging to the section Adenophylli, previously confused with C. campestris.

摘要 巴豆属（Croton）腺叶组（Adenophylli）是该属最大的组，约含223个物种，分布于新热带区。该组的主要鉴别特征之一为蒴果中轴柱，具3枚显著上升的顶端附属物。在对巴西境内该类群开展分类学修订期间，我们发现野巴豆（C. campestris）存在分类界定模糊的问题，常与其他同属物种混淆。本研究通过检视其整个地理分布范围内不同生境下的多份蜡叶标本，对其分类界定展开研究，并开展宏观与微观形态学观察及基于DNA序列的分子分析。本研究结果表明，我们可提出两个新种（C. hatschbachii与C. stellatorotatus），更新野巴豆（C. campestris）和C. subvillosus的命名，并明确上述类群的系统位置、系统发育关系、形态特征及叶片解剖结构。本研究对上述物种进行了详细描述，并讨论了它们的地理分布、形态亲缘关系、花果期及保护现状，同时为两个新种提供了形态插图。本研究共提出17个新异名、13份后选模式标本及2份新模式标本。此外，我们还编制了一份分类检索表，用于鉴别曾与野巴豆（C. campestris）混淆的11个腺叶组类群。