XVI International Botanical Congess

Oceanic islands combine geographic isolation, small size and, often, geologic youth. This has produced biotas of low diversity and complexity. These attributes make oceanic islands ideal locations to study the patterns and processes of speciation. Studies of Hawaiian pteridophytes suggest that species have generally arisen via cladogenetic evolution. High levels of interpopulational and interisland gene flow have undoubtedly inhibited Hawaiian pteridophyte speciation rates. We will present data that suggest that the combination of founder effects and ecological diversity have allowed some groups to experience relatively high levels of speciation. The genus Adenophorus comprises two distinct lineages: one characterized by high levels of morphological species divergence coupled with low levels of genetic divergence, the other by low levels of morphological divergence and high levels of genetic divergence. Speciation via polyploidy is nonexistent among Hawaiian pteridophytes.