Re-collection of Potentially Introduced Symphyotrichum ciliatum (Ledeb.) G. L. Nesom (Astereae, Asteraceae) in Japan after Half a Century

Abstract

The distribution of Symphyotrichum ciliatum, an annual herb mainly occurring in wastelands and wetlands, has been obscure in Japan. So far, it was recorded only from Muroran-shi, Hokkaido, in 1974. We recently recollected it at three populations in southern and central Hokkaido ca. 50 years after the first report of its presence in Japan. All of the populations were likely naturalized because they were in habitats that had been largely impacted by human disturbance. Monitoring the population dynamics of S. ciliatum is required because it occurs at high density and invades wetland habitats where rare species often grow.