Research Notes on Japanese Arisaema (Araceae) ―Its Taxonomy with Special Reference to Plumular Leaf, Number of Ovules per Ovary, and Chromosome Numbers―

Abstract

Arisaema (Araceae) is one of the most diversified genera in Japan (ca. 60 taxa). A paucity of distribution records and misidentification seem to have prevented advance of taxonomic and phylogenetic studies on Japanese Arisaema species. First, the author revised the taxonomy of the A. undulatifolium group based on morphometric analysis and chromosome counts. From the results, six taxa have been recognized in this group, most of them having the same chromosome counts, 2n = 26. Second, from the observation of the seedling morphology and the ovule number of the Japanese Arisaema species, the author found that a plumular leaf shape almost corresponded with the ovule number in sect. Pistillata except A. ringens, and the combination of the two characters seems to be applicable for group delimitation. Many Japanese Arisaema species (25 taxa) are currently faced with extinction. For conservation of these endangered taxa we need to gather more data on their population characteristics (phenology, sex ratio, genetic diversity, pollination, and dispersal). Such information might also give us further insight into the taxonomy and evolution of Japanese Arisaema.