The reproduction and ecology of hypericum edisonianum: An endangered Florida endemic

Abstract

The reproduction and ecology of the narrow endemic and Florida endangered shrub Hypericum edisonianum (Edison's St. John's Wort) was investigated through field and greenhouse studies. Hypericum edisonianum exhibits a number of traits common to rare and geographically limited plant species including heavy reliance on clonal propagation to maintain local stands, passive seed dispersal resulting in a near-parent seed shadow, limited numbers of genetically unique individuals in its isolated seasonal-pond habitat, and likely self-incompatibility. In the field study, most flowers were produced by a small subset of the monitored ramets. Indeed, three ramets belonging to a single genetic individual accounted for 26% of all seed output from the 78 ramets monitored over a one-year period. In spite of strong seed production and germination, seedling establishment appears to occur episodically. The implication is that H. edisonianum is poorly equipped to withstand landscape drainage, agricultural and human development, and climate change. Such impacts will severely challenge the persistence of not only H. edisonianum but also many of the associated species inhabiting Florida scrub. Detailed information is needed about the population-genetic structure of H. edisonianum populations in order to understand its metapopulation structure. Protection of existing and potential H. edisonianum stands is crucial to the long-term preservation this species.