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

Abstract

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 Euphorbia semiperfoliata. It was often considered a subspecies of the widespread European forest plant Euphorbia amygdaloides, or deemed closely related with the western Asian E. macroceras and E. oblongifolia. Here, we explored the evolutionary origin of E. semiperfoliata using nuclear ITS sequences that showed that E. semiperfoliata is divergent from E. amygdaloides and the other species of E. sect. Patellares, which indicates its old, likely Tertiary origin. In addition, its relative genome size is different from E. amygdaloides and other species and several morphological characters revealed by morphometric analyses differentiate E. semiperfoliata from E. amygdaloides. Finally, we provide a taxonomic treatment for E. semiperfoliata, including the typification and a morphological description.