Primary hemiepiphytism and gametophyte morphology in Elaphoglossum amygdalifolium (Dryopteridaceae)

Elaphoglossum amygdalifolium holds a critical phylogenetic position as sister to the remaining ca. 600 extant species of Elaphoglossum and may provide important insight into the evolution of epiphytism in this clade of ferns. Here, we present the first examination of growth habit and gametophyte morphology for this species. We show that the cordate to elongate-cordate gametophytes occur up to 0. 5 m above the ground on the base of tree trunks. Unlike the gametophytes of all other studied species of Elaphoglossum, rhizoids are absent along the thallus margin and the hairs present on the margin lack whitish waxy caps; both differences are pleisiomorphic for the genus. Sporelings of E. amygdalifolium produce a single long root that grows straight into the soil where it branches profusely. Mature sporophytes have long-creeping rhizomes that climb to heights of at least 3 m and produce two types of roots: "feeding roots" that reach the ground and "clasping roots" that anchor the sporophyte to its host plant. Our observations reveal that E. amygdalifolium is a primary hemiepiphyte, the first example of this growth habit to be documented in Elaphoglossum. Results of an ancestral state reconstruction of growth habit in bolbitidoid ferns show that both primary hemiepiphytism and holoepiphytism are equally likely to be the ancestral character state for Elaphoglossum.