Earthstars (Geastrum, Myriostoma) of the Hawaiian Islands Including Two New Species, Geastrum litchiforme and Geastrum reticulatum

An updated, annotated list of earthstars found in the Hawaiian Islands is presented that includes 19 species of Geastrum and Myriostoma coliforme. Favored habitats for these gasteroid fungi include periodically wet windward coastal Casuarina groves, windward Leucaena thickets, and leeward coastal Prosopis groves. In contrast to these nonnative vegetation zones, earthstars such as Geastrum minimum, G. campestre, and G. corollinum are found also in largely native leeward montane Sophoral/Myoporum forests, whereas Geastrum velutinum and G. reticulatum appear in montane native Acacia koa/Metrosideros forests. Eighty-two percent of the collections were made between September and February, although Geastrum triplex may be found earlier during the summer months. Two species, Geastrum litchiforme Desjardin & Hemmes and Geastrum reticulatum Desjardin & Hemmes, are described as new, accompanied by illustrations and comparisons with allied taxa. Geastrum xerophilum, originally published without Latin diagnosis, is formally validated. Specific collections are documented and island distribution and preferred habitats of the various species are listed. An artificial dichotomous key to aid in identification is provided.