Reporting a new weedy Euphorbia species from Iran.
Human activities specially increasing international trades during last century such as import and export of agricultural products make to occur many alien species in new regions. Some of these species cause major economic and environmental damages to biodiversity and agriculture (Pimentel 2009). Most exotic plants introduced and established in Iran ecosystems were introduced for ornamental purposes (Pahlevani & Sajedi 2011). Among three main phytogeographical regions of Iran, Irano-Turanian, Hyrcanian and Sahara-Sindian, the two last ones in north and south Iran respectively have no annual freezing temperature for a longtime and it has made these regions have vulnerable and fragile ecosystems to introduced and alien plant species. Genus Euphorbia L. with eight introduced species is the largest group of flowering plants in Iran with weedy or invasive behavior (Pahlevani & Riina 2011). All eight neophytes have New World origin and belong to subgen. Chamaesyce Raf. Of the eight introduced species, five belong to sect. Anisophyllum Roep. subsect. Hypericifoliae Boiss. (Pahlevani et al. 2020). Although the members of the subsection have C4 photosynthesis pathway, they occur in temperate, warm temperate and tropical regions. The weediness of this group is facilitated by quick generation turnover (several generation per growing season), creeping habit, high seed set, and long-distance seed dispersal (Yang & Berry 2011). During the recent fieldwork in S Iran (Kerman province), a weed specimen of Euphorbia was collected from Henna field at Jiroft Research Center that did not match the descriptions of any known Iranian species.