Marasmius koae to the substrate. The fruit body has no distinctive taste or odor. The thin-walled spores are somewhat fusoid (spindle-shaped) to elongated ellipsoidal in shape, smooth, hyaline (translucent), and measure 12–14.5 by 4–4.8 μm. The basidia (spore-bearing cells) are club-shaped, four-spored, and clamped, measuring 24–28 by 7–9 μm. The species is endemic to Hawaii, where it has been found growing in dense groups on the rotting wood of koa ("Acacia koa"). Collections have been made only in the Koa/Ohia Montane Wet Forest on Kauaʻi island. Marasmius koae Marasmius koae is a species of agaric fungus in the Marasmiaceae family. Newly described
Acacia koa confirmed this close relationship; the estimated time of divergence is about 1.4 million years ago. "A. heterophylla" sequences nest within those of the more diverse "A. koa", making the latter paraphyletic. Both species are thought to be descended from an ancestral species in Australia, presumably their sister species, "Acacia melanoxylon". Dispersals most likely occurred via seed-carrying by birds such as petrels. Both species have very similar ecological niches, which differ from that of "A. melanoxylon". A closely related species, koaia or koaie ("A. koaia"), is found in dry areas. It is most easily distinguished by having smaller seeds that are