New Advances in Fern Ecology
Watkins, Jr., James E. , Mack, Michelle C. , Mulkey, Stephen S. .
Comparative functional ecology of tropical epiphytic and terrestrial fern gametophytes.
FERNS rely on wind-dispersed spores that germinate into free-living haploid gametophytes. The independent gametophyte has been ignored in the ecological literature, yet this stage of the life cycle may be critical in shaping species distributions. The goal of this study was to develop an understanding of gametophyte demography and the role of extreme stress tolerance and nitrogen nutrition in shaping the distributions of tropical fern gametophytes. We utilized demographic techniques, chlorophyll fluorescence, measurements of δ 15N natural abundance and uptake kinetics to accomplish these goals. Gametophyte demography of two terrestrial, two epiphytic, and one hemiepiphytic species was studied over a period of 2 years. The longevity of epiphytic species ranged from 16-25 months whereas terrestrial species ranged from 4 to 11 months. Percent recruitment varied with epiphytes exhibiting higher to equivalent recruitment yet significantly slower rates compared to terrestrial species. To determine the role of extreme stress tolerance in gametophyte survival we conducted a survey of desiccation tolerance of several species to: 1) a single desiccation event, 2) different desiccation intensities and 3) multiple desiccation cycles. All species exhibited physiological recovery following a single desiccation event however; the extent of recovery differed among species and was closely linked to species ecology. Both intensity and the number of desiccation cycles clearly influenced recovery with species of xeric habitats exhibiting greater tolerance than mesic species. In our N nutrition study, we found that ferns can partition N by form and that form preference varied with greater dependence on organic N in the epiphytic vs. terrestrial species. These data suggest that there are fundamentally different nutrient use strategies between the two groups. Taken together, the data from this study suggest that adaptively meaningful variation exists within fern gametophytes and such variation may be important in shaping gametophyte and potentially sporophyte distributions.
Log in to add this item to your schedule
1 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Monday, July 31st, 2006
Time: 8:15 AM