First record of Gamochaeta americana as alien species from Iran

During the assessment and monitoring of Hyrcanian forests, an alien species, Gamochaeta americana (Mill.) Wedd (Asteraceae) was observed and identified from the forests of Gilan province (north of Iran). The new alien plant grows in disturbance and roadside in the forest dominated or co-dominated by Quercus castaneifolia and Carpinus betulus. Gamochaeta americana is native to the new world but has been able to be introduced around the world. This paper provides a detailed description, distribution map, photographs, and diagnostic features, which will help prepare a continuous monitoring and management plan. Considering the traits of this new alien plant, which has high reproductive potential, G. americana can have a wide distribution in Iran. Therefore, further field investigations on its distribution and prioritizing, an eradication intervention for this alien weed is suggested before it spreads widely and aggressively.