Phylogenetic relationships of Origanum taxa (Lamiaceae) from Greece: Initial insights from molecular and morphological data

Abstract

The genus Origanum is a well-known culinary, aromatic and medicinal taxon of the Lamiaceae family. Despite the notable progress that has been made in Lamiaceae phylogenetics and in the Nepetoideae subfamily, the genus remains insufficiently investigated concerning its interspecies evolutionary relationships. The present study provides initial insights into the phylogenetic relationships and sectional classification of Greek taxa, based on three nuclear and five chloroplast DNA regions with eight taxa and 68 samples in total. The molecular results showed all (steno) endemic species as monophyletic with high or absolute support. Additionally, O. calcaratum?s scattered distribution between three phytogeographical areas in the Aegean Archipelago is also confirmed molecularly. The molecular results also verify the close affinity of certain sections; thus, sec. Majorana is placed as a sister group of sec. Chilocalyx and sec. Amaracus with sec. Anatolicon. However, based on species sectional classification, the groups from this study differ from the sections previously recognized. Such species belong to sections Amaracus and Anatolicon, where they are either mixed together or are grouped with other sections. Regarding morphological analysis, certain non-vegetative characters are highlighted as important for the delimitation of most Greek taxa, while characters related to the calyx, when combined, are very useful for the delimitation of sections.