The relative utility of coding and non-coding chloroplast DNA in phylogenetic and biogeographical analyses of Cibotium (Cibotiaceae) and Diplopterygium (Gleicheniaceae)

Abstract

This study investigated the relative utility of five different coding and non-coding regions in chloroplast DNA to determine which region was most useful in resolving phylogenetic relationships among species of Cibotium and Diplopterygium. It also incorporated these data into an ongoing biogeographical study that focused on the origins and pathways of dispersal of ferns to Hawaii. Taxon sampling and DNA extraction were conducted on seven species of both Cibotium and Diplopterygium plus outgroups for each genus. Maximum parsimony heuristic and bootstrap analyses (as implemented in PAUP*) were performed on single genomic region data sets and on combined data sets for each genus. Results showed that non-coding regions were more useful in resolving relationships than the coding regions. However, the trnG-R region, which is both coding and non-coding, was the most useful region for resolving relationships overall. The combined analyses for both Cibotium and Diplopterygium suggested a more resolved tree than individual analyses and suggested possible dispersal mechanisms of ferns to Hawaii. Evidence for ancestral dispersal via the jetstream was the most probable dispersal mechanism based on distribution of closest relatives for species of both Cibotium and Diplopterygium.