XVI International Botanical Congess

Occurrence patterns of epiphytic ferns on the trunks of seven trees of Hyeronima alchorneioides (Euphorbiaceae) are compared to those of terrestrial pteridophytes at the La Selva Biological Station in Costa Rica. Twenty-one species of epiphytic ferns and 20 terrestrial ferns were recorded, with only 1 species occurring in both habits. Based on fern composition, trees could be divided into 3 zones. The crotch zone was dominated by Oleandra articulata, Elaphoglossum herminieri and Vittaria stipitata.The buttress zone was dominated by Trichomanes eckmanii, T. godmanii, and Vittariaceae gametophytes. There were few bole-specific ferns and this zone (extending between buttress and crotch) was consistently low in percent cover by fern species. In percent cover and number of species, simple leafed ferns dominated the epiphytic condition, whereas ferns with dissected leaves dominated the terrestrial flora.