RAPD Variation in Temperate Populations of the Epiphytic Orchid Epidendrum conopseum and the Epiphytic Fern Pleopeltis polypodioides

Abstract

Although 10% of all vascular plant species are epiphytic, few studies of genetic diversity in epiphytes have been completed. We used random amplified polymorphic DNA (RAPD) markers to investigate genetic diversity in temperate populations of the epiphytic orchid Epidendrum conopseum and in the epiphytic fern Pleopeltis polypodioides (resurrection fern). Three populations of each species were sampled in North Carolina and South Carolina, totaling 52 plants of E. conopseum and 20 specimens of P. polypodioides. Seven random primers produced 11 polymorphic RAPD markers in E. conopseum, while three primers yielded 14 variable markers in P. polypodioides. An analysis of molecular variation partitioned 85.1% of the variation within populations of E. conopseum and only 14.9% among populations. Pleopeltis polypodioides was found to maintain slightly greater population subdivision, with 76.4% of the total variation within populations and 23.6% among populations. The results suggest extensive gene flow among populations of both species, particularly in E. conopseum. The lack of population differentiation in these epiphytes may be associated with the effective wind dispersal of spores and seeds from the canopy habitat.