Sisymbrium irio l. (brassicaceae): A new alien plant in Korea

Abstract

As anthropogenic transports of biomaterials have rapidly escalated in the past century, biological invasions have been of great concern on a global scale. Given the exponential growth of alien species passing through the initial point of introduction, reporting an alien species on its initial appearance is important. Sisymbrium irio, an annual herb distributed widely throughout the northern hemisphere, is a notorious weed for its strong invasiveness. In 2016 S. irio was first reported in Korea. The plant was found along the urban expressway, Beonyeong-ro, connecting Busan trading port to Gyeongbu expressway. To properly identify the species, we collected ten S. irio samples from the reported site and examine their morphological characters. The identification key of Sisymbrium irio and its related species in the genus was constructed to clarify taxonomic confusions. We further determined the identity of the taxa by inferring the phylogeny of S. irio and the related taxa. To investigate the distribution changes for the past four years since the first observation in 2016, we monitored the area in late summer of 2020. Both morphological and molecular examinations indicated that the Sisymbrium species we found in Korea for the first time was S. irio. From our site monitoring, we newly found a second distribution site that is approximately 1.5 km away from the original site. Considering the geographical proximity of the introduction sites from the port, we hypothesize that S. irio might started expanding its range by the aid of roads. Given the role of roads as a corridor for alien species, further expansion of S. irio in Korea is expected.