Ecotypic variation in plant characteristics for Origanum vulgare subsp. hirtum populations

► 30 populations of O. vulgare subsp. hirtum are shown to be different ecotypes. ► Higher essential oil concentrations occur in the more xeric and thermal environments. ► Production of essential oils has a cost to plants with respect to their growth. ► It is argued that essential oils helped plants endure drought and heat stresses.