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
Hawaiian tropical rainforests milo ("Thespesia populnea") for the past 1,000–2,000 years. The Polynesian-introduced noni ("Morinda citrifolia"), pia ("Tacca leontopetaloides"), and kī ("Cordyline fruticosa") are also common in this zone. Other native species include pololei ("Ophioglossum concinnum"), ākia ("Wikstroemia" spp.), loulu fan palms ("Pritchardia" spp.), ōhia lehua ("Metrosideros polymorpha"), and lama ("Diospyros sandwicensis"). Mixed mesic forests, at on the windward slopes of the large islands in addition to the summit of Mount Lānaihale on Lānai, receive of rainfall annually and thus may not be true rainforests. The forest canopy, dominated by koa ("Acacia koa") and ōhia lehua ("Metrosideros polymorpha"), is somewhat open, but tree