MYCORRHIZAE IN HAWAIIAN ANGIOSPERMS - A SURVEY WITH IMPLICATIONS FOR THE ORIGIN OF THE NATIVE FLORA

Endemic, indigenous, naturalized and cultivated angiosperms growing in a variety of habitats in Hawaii were examined for mycorrhizae. Of 147 species (representing 61 families) examined, 122 were mycorrhizal, and 98% of the latter formed vesicular-arbuscular mycorrhizae (VAM). Ericoid, orchid, and ectomycorrhizae also were found. Mycorrhizae were most frequent in endemic species (90.3%) and least in indigenous species (71.9%). The incidence of mycotrophy in Hawaiian endemic species was significantly greater than in mainland species. In addition, VAM often were found in species belonging to families that typically lack mycorrhizae (Aizoaceae, Brassicaceae, Caryophyllaceae, Cyperaceae, Hydrophyllaceae, Juncaceae, Pandanaceae, and Urticaceae). Naturalized weedy species were highly mycorrhizal. The high incidence of mycorrhizae in endemic species suggests that VAM fungi and obligately mycotrophic plant species may have been present in the Hawaiian Islands from the earliest stages of the development of the angiosperm flora.