Genetic variation in morphology and growth characters of Acacia koa in the Hawaiian Islands

Substantial phenotypic variation in Acacia koa has been reported in the Hawaiian Islands. We grew 72 A. koa families from the islands of O'ahu, Kaua'i, and Hawai'i in two common gardens to determine whether phenotypic differences in phyllode morphology, extrafloral nectary morphology, and other characters have a genetic basis. Significant differences among islands and families were observed for phyllode width, curvature, and pubescence, as well as extrafloral nectary size and pigmentation, retention of juvenile leaves, and branch bark color. Seed shape also differed significantly among islands. Discriminant analysis revealed that families from the island of Hawai'i are distinct from O'ahu and Kaua'i families. The O'ahu and Kaua'i families, however, could not be reliably distinguished based on sapling morphology or growth characters.