A Taxonomic Study of the Arisaema serratum Group (Araceae) in Northern Okayama Prefecture, Western Japan

Abstract

Of about 180 species of Arisaema (Araceae), 53 species are distributed in Japan. In Japanese Arisaema, the Arisaema serratum group includes many species difficult to distinguish from each other because of a lack of decisive taxonomic characters between them. In May 2014, the fi rst author found that some populations of the Arisaema serratum group occur with A. ovale Nakai in Ohgaya, Nishiawakura-son, Aida-gun, Okayama Pref., western Japan. We have observed their native ecological and morphological features in the fi eld and compared with other populations in neighbouring areas. As a result, the populations were composed of four Arisaema species: A. maekawae J. Murata & S. Kakishima, A. angustatum Franch. & Sav., A. peninsulae Nakai, and A. pseudoangustatum Seriz. var. pseudoangustatum.