Format: ORAL

Ricarda Riina

Real Jardín Botánico (RJB), CSIC, Madrid, Spain

The family Euphorbiaceae includes two of the most-species rich genera of flowering plants: Croton (~1300 species) and Euphorbia (~2060 species). Euphorbia is clearly defined by its highly specialized and unique inflorescence, the cyathium, while Croton is distinguished by a suite of morphological features. Taking their global distributions together, species of both or either of these genera are present in almost all biomes of the world. Many species are important for a variety of traditional human uses and for the development of products in the pharmaceutical and other industries. Numerous weeds and pioneer species are present in both genera, while ornamentals of high commercial value are common in Euphorbia. A robust phylogenetic framework is available for Euphorbia based on both Sanger sequencing and genomic data. Many of the recent advances in the systematics of Euphorbia have been focused on groups or species complexes distributed in Eurasia, Macaronesia and Africa. Unlike Euphorbia, phylogenetic relationships within Croton remain largely unresolved at deep and shallow nodes, but preliminary analyses using genomic data (HybSeq) show promising results for resolving the genus backbone as well as species relationships within its main clades or sections. Recent developments in our knowledge of Croton include the discovery of new clades, clarification of phylogenetic relationships and taxonomy of important sections, and the increasing incorporation of anatomical characters and development approaches in morphological studies, including both vegetative and floral structures. These have provided new insights into the evolutionary success of Croton in arid or seasonally dry habitats, and into the evolution of chemical and physical defenses against herbivores and pathogens. Major gaps in the biological knowledge of the two genera are highlighted, including suggestions for key questions to be addressed in future studies.