Summary: The Contributions of Population Studies on Ferns

Abstract

The preceding papers have presented a wide array of investigative approaches centered on the dynamics of population phenomena in ferns. Collectively, these studies have addressed all phases of the fern life cycle: spore production and dispersal, gametophyte establishment, mating mechanisms and their evolution, and both genetic and demographic attributes of sporophytes. Represented in these studies are some of the shifts in emphasis and approach that characterize recent trends in population ecology: attention to all stages of the life cycle (including the challenging and important study of gametophytes in nature), coordination of field data with laboratory studies (e.g. isozyme analysis, tests for antheridiogen response, estimation of genetic load), and development of theoretical models that predict outcomes of dynamic processes (e.g. evolution of mating systems) based on biological features of the organisms being modeled. Taken together, these studies begin to draw a picture of how ferns and other pteridophytes establish and maintain populations in nature, a picture that as yet is incomplete. While recent investigations have taken us strides forward in our understandings of fern populations, additional knowledge will emerge only after considerably more effort. With the goal of encouraging such effort, we would like in this symposium summary to point out the potential for additional research that will deepen our understanding of the biology of ferns as representatives of plants and of organisms in general. Below, as we order our thoughts principally along life history stages, we will attempt to bring together some of the concepts generated by the symposium papers, and also to identify areas of uncertainty that are of particular interest for future investigation.