Origin and diversification of Hawaiian Dryopteris (Dryopteridaceae)

This dissertation research focussed on the molecular systematics, historical biogeography, and genetic differentiation of Hawaiian members of the fern genus Dryopteris Adans. (Dryopteridaceae). In Chapter One I provide an introduction to the Hawaiian Islands and the flora of Hawaii. There are high levels of endemism of both flowering plants and pteridophytes in Hawaii. Pteridophytes comprise one fifth of the vascular plant flora of Hawaii and are relatively understudied compared to flowering plants. In Chapter Two I discuss the molecular systematics and historical biogeography of Hawaiian Dryopteris. All but one of the Dryopteris species in Hawaii are endemic. Phylogenetic analyses based on chloroplast DNA data strongly suggested that Dryopteris in Hawaii is not monophyletic and that there have been at least five separate colonizations of Hawaii by different species of Dryopteris. This pattern is much different than has been hypothesized for many groups of angiosperms in Hawaii. In Chapter Three I present evidence, based on chloroplast DNA analyses of a subset of Dryopteris species, that current subgeneric and sectional classifications of the genus Dryopteris do not accurately reflect phylogenetic history. In light of these analyses, classifications within the genus should be reassessed. I discuss genetic differentiation among five of the eight members of the most taxonomically contentious group of Hawaiian Dryopteris in Chapter Four. The analyses based on Inter Simple Sequence Repeats (ISSRs) indicated there are two genetically distinct groups within this so called “glabra group.” Contentious taxa that have been considered both species and varieties by different workers were not genetically differentiated by this method. In Chapter Five I present a preliminary investigation of the utility of outline-based morphometrics and eigenshape analysis for discriminating among taxa based on leaf shape variation. The same five glabra group taxa analyzed in Chapter Four were used. Outline-based morphometric analyses appear to be useful tools for discriminating taxa. The same taxa that were genetically separated were also morphologically separated. In Chapter Six I summarize the main findings from each chapter of the dissertation and discuss the conservation implications of my research.