Occurrence and habitats of CAM plants distributed in Japan.
Crassulacean acid metabolism (CAM), the photosynthetic pathway that minimize water loss and the plants with CAM occupy hot and semi-arid regions. Recently, there has been increased attention to CAM plants that may serve as stable production under climate change and are cultivated for experiments. CAM plants live in variable environments on the earth as tropical epiphytes, halophytes, and aquatic macrophytes. Therefore, we would find them in variable environments in Japan. However, we have little information on the species and their habitats. In this study, CAM plants occurring in Japan are listed, especially the habitats, as a first step to understand the ecology of CAM plants by using domestic and foreign literature. There are 23 families, 83 genera, 237 CAM species in total in Japan. They are comprised of five submerged aquatic species of lycopodiophyte, Isotaceae, four epiphytic ferns of Pteridophyte, only one gymnosperm, Welwitschia mirabilis and in Magnoliophyta, one species of Piperaceae, 7 families 25 genera 86 monocots and 11 families 53 genera 140 eudicots. There are 185 cultivated species, which occupied about 80% of CAM species in Japan. There are also 56 native species in Japan, and almost of them live under water-limit condition such as on the rock or by the seaside. Although there are 33 naturalized species, CAM belonging to Rubiaceae and etc have not been found in Japan.