title: Ecological factors influencing growth of the endangered Hawaiian fern Marsilea villosa (Marsileaceae) and implications for conservation management.
abstract: OBJECTIVE
  Conserving endangered plants is a complex task, and practitioners must often use a "triage" approach, addressing only immediate needs. Ecologists can improve this process by conducting sound science upon which to base management. Marsilea villosa is an endangered, endemic Hawaiian fern with seven remaining populations in ephemerally flooding drylands. Among its uncommon traits are long-lived sporocarps, requiring flood and drought to complete its sexual life cycle, and extensive vegetative growth.
  
  
  METHODS
  We conducted a 3-yr ecological field study, measuring percent cover of M. villosa and associated species, flooding depth, and canopy cover, to identify ecological factors with the greatest impact on M. villosa growth.
  
  
  RESULTS
  Maximum flooding depth and canopy cover had strong positive relationships with M. villosa growth, and all plots with >50% threshold of either variable reached 100% cover of M. villosa by the end of the study. Interaction effects explained nuances of these relationships, including synergy between the two variables. Percent cover of nonnative functional groups (graminoids and nongraminoids) each had negative relationships with M. villosa growth, but interactions showed that nongraminoid cover was driven by particular species, and that time since flooding had greater influence on M. villosa growth than graminoid cover.
  
  
  CONCLUSIONS
  We recommend planting reintroduced populations in flood-prone areas with moderate shade, experimental outplanting of native plants with M. villosa, and management of graminoids as a functional group, while nongraminoid management should be species-specific. These practices will promote self-sustaining populations and reduce the need for labor-intensive management.
authors.affiliation: Department of Botany, University of Hawai'i at Mānoa, Honolulu, Hawai'i 96822, USA. mmchau@hawaii.edu
authors.forename: Marian M
authors.initials: MM
authors.lastname: Chau
authors.forename: Whitney R
authors.initials: WR
authors.lastname: Reyes
authors.forename: Tom A
authors.initials: TA
authors.lastname: Ranker
mesh_terms: D018533:Biomass; D003247:Conservation of Natural Resources; D055864:Droughts; D017753:Ecosystem; D056727:Endangered Species; D055868:Floods; D006254:Hawaii; D043964:Marsileaceae / Q000254:growth & development / Q000502:physiology*; D008954:Models, Biological; D013045:Species Specificity
keywords: competition; ecological interactions; ephemeral pools; facilitation; flooding; restoration; shade