Biogeographic origin of the Hawaiian pteridophyte, Diplopterygiutn pinnatum, (Gleicheniaceae) as assessed by phylogenetic analysis of atpfi and trnG-R chloroplast DNA regions

Abstract

Despite the fact that pteridophytes, commonly known as ferns, account for a large percentage of Hawaii’s vascular plants, few studies have been conducted to determine their biogeographical origins. This study aimed to determine an origin and a pathway of dispersal for the endemic Hawaiian fern, Diplopterygium pinnatum (Gleicheniaceae). Molecular and evolutionary phylogenetic analysis was employed using obtained chloroplast DNA sequences from the gene atpfi and the genes and noncoding spacer region trnG-R. Combined analysis with trnL-F and rbcL sequences from another study was also performed. Taking into account conclusions from a previous study, two possible origins and dispersal mechanisms were considered. The first hypothesis was that D. pinnatum originated in the Indo-Pacific region and was dispersed through spores in the Pacific jetstream. The second hypothesis was that D. pinnatum was dispersed to Hawaii via ITCZ/Hadley Cell Shift from an origin somewhere in the Austral region of the Pacific Ocean. Maximum likelihood and maximum parsimony trees produced similar relationships with similar bootstrap support. However, this study failed to differentiate between the two hypotheses and therefore the most likely origin and dispersal mechanism could not be determined.