Conservation of the endangered Hawaiian fern 'ihi'ihilauākea (Marsilea villosa) : a synthesis of experimental restoration, community ecology, and population genetics

Ph.D. University of Hawaii at Manoa 2012.Includes bibliographical references.Conservation of endangered plants is a critical step in maintaining and restoring global biodiversity. Management efforts such as in situ conservation and restoration through plant reintroduction are more likely to be successful if decisions are based on carefully designed scientific research. Marsilea villosa is an endangered, endemic Hawaiian fern with only seven remaining populations on the islands of O'ahu and Moloka'i restricted to ephemerally flooding dry lowlands. Among its uncommon traits are long-lived sporocarps (i.e., highly modified leaves with drought resistant walls containing sporangia and spores), a requirement of flood and drought to complete its sexual life cycle, and extensive vegetative growth. In this dissertation I conducted three studies to answer the following questions: 1) Which management techniques best facilitate growth of M. villosa in outplanting for reintroduction? 2) Which ecological factors affect the growth of M. villosa under field conditions? 3) How much genetic variation exists within and among M. villosa populations? 4) What are the implications of these studies for how M. villosa is managed? I conducted a restoration experiment to evaluate the effects of light, flooding, weeding, and their interactions on the growth of M. villosa outplanted in a common-garden. I found that the combination of flooding and shade treatments promoted the greatest increase in M. villosa growth, and that the effects of this interaction grew stronger over time. After drought occurred, shade also increased M. villosa growth in the absence of weeding. In a three-year field study, I examined ecological factors that influenced M. villosa growth and confirmed that shade and flooding have positive synergistic effects, while the negative effects of associated non-native species differ with functional groups. In a population genetic study, the majority of genetic variation was found at the subpopulation level, but there was also genetic structure that showed strong differentiation among some populations and between the two islands. This research provides several explicit management recommendations that will increase the chances of success in conservation and restoration of Marsilea villosa, and a model upon which to base restoration of the more resilient endangered species in Hawaiʻi and worldwide