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

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.

Automated summary

The taxonomic circumscription of C. campestris in the largest section of the Croton genus, Adenophylli, was found to be problematic. Through morphological, molecular, and geographic analyses, two new species were proposed and the nomenclature of existing species was updated. The study provides detailed descriptions of the species' morphology, geographic distribution, and conservation status.