Acacia heterophylla 1.4 million years ago. "A. heterophylla" sequences nest within those of the more diverse "A. koa", making the latter species paraphyletic. Both species are descended from an ancestral species in Australia, presumably their sister species, "Acacia melanoxylon"; the means of dispersal to Hawaii and then to Réunion (the latter trip a distance of 18,000 km) is thought to have been seed-carrying by birds such as petrels (the seeds of these species are not adapted for prolonged immersion in seawater). Both species also have very similar ecological niches, which differ from that of "A. melanoxylon". Acacia heterophylla Acacia heterophylla, the highland
Acacia koa survives best in pasture when planted under koa. This is because koa trees reduce radiative cooling, preventing frost damage to ōhia lehua seedlings. Koa is the preferred host plant for the caterpillars of the green Hawaiian blue ("Udara blackburni"), which eat the flowers and fruits. Adults drink nectar from the flowers. Koa sap is eaten by the adult Kamehameha butterfly ("Vanessa tameamea"). The koa bug ("Coleotichus blackburniae") uses its rostrum to suck the contents out of koa seeds. Koa is vulnerable to infection by koa wilt. Acacia koa Acacia koa is a species of flowering tree in the pea family,