Dispersal ecology of the maritime plants in the Ryukyu Islands, Japan

Abstract

The dispersal ecology of seventeen maritime species, which are dominant and/or characteristic species of coastal communities on the Ryukyu Islands, was studied. The species wereCalophyllum inophyllum, Canavalia maritima, Clerodendron inerme, Guettarda speciosa, Hernandia sonora, Hibiscus tiliaceus, Ipomoea gracilis, I. pes-caprae, Messerschmidia argentea, Pandanus odoratissimus, Pongamia pinnata, Scaevola frutescens, Sophora tomentosa, Terminalia catappa, Thespesia populnea, Vigna marina andWedelia biflora. The structure and size of disseminules and their buoyancy and viability in seawater were examined in the laboratory. The disseminules of these seventeen species have morphological characteristics for buoyancy, and tests showed that these species could be dispersed by sea currents. Drift disseminules on the drift line, seedlings on the hightide line, and young plants of woody species in the herb zone were observed, being abundant on the coasts of the Ryukyu Islands. The Kuroshio Current carries these disseminules from islands where these species form part of the tropical coastal vegetation.