Biogeographical Origins and Phytogeny of the Endemic Hawaiian Species ofCibotium (Dicksoniaceae): a Molecular Perspective Based on atpb Sequences

Abstract

A great deal of speculation exists as to the biogeographical origins and phylogeny of endemic Hawaiian ferns; yet only a handful of studies has actually examined the evolution of these endemics and their relationships to continental species. The fern genus Cibotium (Dicksoniaceae), consisting of four Hawaiian endemics and five non-Hawaiian species, is the focus of this study. The goals of my research were to resolve whether Hawaiian Cibotium is monophyletic and to test the hypothesis that the common ancestor of Hawaiian Cibotium originated from the IndoPacific region. Although the long-distance dispersal mechanism of fern spores to Hawaii was not directly investigated, a pathway for the colonizing ancestor can be inferred based on the geographical location of the closest non-Hawaiian relative. The chloroplast DNA fragment atpfi was sequenced for eighteen taxa and phylogenetic analyses were performed using both maximum parsimony and maximum likelihood. These analyses strongly indicate that the genus Cibotium is monophyletic and suggest that the colonizing ancestor of the Hawaiian species is of South American origin. From this we may infer that the ancestral spores arrived on Hawaii via the combined effects of Hadley cells, trade winds, and seasonal shifts in the inter-tropical conversion zone (ITCZ).