The morphologically variable tree fern Alsophila hornei of the Gymnosphaera clade is taxonomically and ecologically evaluated. While there is only one morphospecies present at the type locality on Fiji, three species can be characterized along an elevational transect on New Guinea. Alsophila hornei is also present at low elevations throughout New Guinea. Alsophila phlebodes is newly described and so far only found at high elevations on the Vogelkop Peninsula of New Guinea. Among its sympatric congeners, it stands out by having relatively pale brown petiole scales and well-developed, highly dissected remote basal pinnae on the petioles that form a wig-like structure around the trunk apex. Alsophila olivacea is reinstated and separated from A. hornei and A. phlebodes mainly by lacking adventitious pinnae and having an intermediate elevational distribution in the mountains of New Guinea. A key to the Australasian species of the Gymnophaera clade is provided in order to facilitate taxonomic studies of this biogeographically and phylogenetically interesting group.