Humidophila gen. nov., a new genus for a group of diatoms (Bacillariophyta) formerly within the genus Diadesmis: species from Hawai'i, including one new species

While conducting surveys of freshwater algae from the Hawai'i Islands, we encountered several diatom species and populations belonging to the genus Diadesmis, subgenus Paradiadesmis. Upon closer examination of valve morphology with scanning electron microscopy, the species and populations assigned to Paradiadesmis differed considerably in structure and microhabitat fidelity from Diadesmis confervacea Kutzing, the type species of the genus Diadesmis. The Hawai'i species have each stria composed of a single elongate areola, external distal raphe ends that are straight to curved, and fine hymenate occlusions on the interior of the areolae. These structures are not found in D. confervacea. Therefore, we propose a new genus, Humidophila, to accommodate these taxa formerly belonging to the subgenus Paradiadesmis. One new species from the Hawai'i Islands is described and 47 former Diadesmis species are transferred to Humidophila.