A new species and molecular phylogeny of Brazilian succulent <i>Euphorbia</i> sect. <i>Brasilienses</i>

A new species of <i>Euphorbia</i> sect. <i>Brasilienses</i> V.W. Steinm. &amp; Dorsey is described. <i>Euphorbia tetrangularis</i> Hurbath &amp; Cordeiro is endemic to the Serra de Montevidéu, a part of the Espinhaço Range located in the state of Minas Gerais, Brazil. It differs from other species within the section based on the following characters: 4-ribbed branches, green cyathia, and green cyathial glands with erect appendages. This new species would qualify as critically endangered (CR) according to IUCN criteria. An inferred phylogeny based on a combined dataset of nuclear (ITS1) and plastid regions (<i>psbA-trnH</i>, <i>trnC-ycf6</i>, <i>matK</i>, <i>atpI-atpH</i>, <i>psbJ-petA</i>, <i>trnQ-rps16 × 1</i>) confirms the monophyly of <i>Euphorbia</i> sect. <i>Brasilienses</i> and supports the recognition of <i>E. tetrangularis</i>. The phylogeny also suggests that this group probably underwent a recent radiation.