PARENT SESSION
Oral Session # 62: Biodiversity I.
Presiding: P Baker
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 100.
Diversity and abundance of epiphytic (canopy and understory) and terrestrial ferns along an elevational gradient: Implications for dispersal and migration.
Watkins, James*,1, Cardelus, Catherine1, Moran, Robbin2, 1 University of Florida, Gainesville, FL, USA2 New York Botanical Garden, Bronx, NY, USA
ABSTRACT- Along a continuous wet forest elevational gradient in Costa Rica, 30-3000m, we examined the distribution and diversity of pteridophytes, both epiphytic and terrestrial, at each of six sites: 2600m, 2000m, 1600m, 1000m, 500m and 30m. To determine terrestrial and understory (low trunk) epiphytic species diversity and abundance, 4: 100m x 4m transects were laid out in randomly chosen areas at each site. Transects were subdivided into 5m x 4m quadrats in which both diversity and abundance were recorded. To determine diversity and incidence of canopy species, we climbed ten individual canopy trees per site except at 2600m where 5 individuals were studied. Two: 4m by 0.5m canopy transects, subdivided into 0.5m x 0.5m quadrats, were laid out and all ferns found in these quadrats were sampled and their presence recorded. Thus far, a total of 276 species of pteridophytes in 61 genera were recorded along the entire gradient: 114 canopy epiphytes, 122 understory epiphytes and 79 terrestrial species. Pteridophyte diversity shows a clear mid-altitudinal bulge at 1000m for rarefied data. Predictably, overlap of species among elevations decreases with increasing distance between sites. Overlap among habitats is higher between the canopy and understory epiphyte communities (18%) while overlap of both epiphytic groups with terrestrial species is 0 and 1 species respectively. The differences in overlap suggest extreme recruitment limitation on local and regional scales in a dispersal unlimited system.
Key words: epiphyte, elevation, fern, diversity