A new species of Croton (Euphorbiaceae) endemic to the Brazilian Pampa and its phylogenetic affinities

Croton guaritensis, sp. nov. is here described, illustrated, and classified based on morphological and molecular data. The new species is restricted to the Pampa biome where it grows around rocky outcrops. Examination of the morphology from herbarium collections and field observations, as well as evidence from molecular analysis, indicate that Croton guaritensis belongs to Croton section Barhamia subsection Medea. Croton subsection Medea is represented by several rare and endemic species and stands out by its glandular structures in stipules, bracts, and sepals. The new species differs from other species of this subsection in the indumentum on branches and leaves, which consists of subentire lepidote trichomes, and in the sepals of staminate and pistillate flowers that have stipitate glands. An identification key to the new species and closely related taxa in southern Brazil is provided, as well as a preliminary conservation status