An integrative approach supports the taxonomic distinction of the Sardo-Corsican endemic <i>Euphorbia semiperfoliata</i> from the widespread <i>E. amygdaloides</i> (Euphorbiaceae)

In the western Mediterranean, Corsica and Sardinia are characterised by high plant diversity and endemism, and exhibit a tight biogeographic connection. One of the endemic taxa thriving in forests, macchia, along riversides and in mountain grasslands of both islands is <i>Euphorbia semiperfoliata</i>. It was often considered a subspecies of the widespread European forest plant <i>Euphorbia amygdaloides</i>, or deemed closely related with the western Asian <i>E. macroceras</i> and <i>E. oblongifolia</i>. Here, we explored the evolutionary origin of <i>E. semiperfoliata</i> using nuclear ITS sequences that showed that <i>E. semiperfoliata</i> is divergent from <i>E. amygdaloides</i> and the other species of <i>E.</i> sect. <i>Patellares</i>, which indicates its old, likely Tertiary origin. In addition, its relative genome size is different from <i>E. amygdaloides</i> and other species and several morphological characters revealed by morphometric analyses differentiate <i>E. semiperfoliata</i> from <i>E. amygdaloides</i>. Finally, we provide a taxonomic treatment for <i>E. semiperfoliata</i>, including the typification and a morphological description.