title: Significant spatial aggregation and fine-scale genetic structure in the homosporous fern Cyrtomium falcatum (Dryopteridaceae).
abstract: Spores of homosporous ferns are small, wind-borne and thus have the potential for long-distance dispersal. This common perception has led to a prediction of near-random spatial genetic structure within fern populations. Spore dispersal and spore bank studies, however, indicate that most spores fall close to the maternal plant (< 5 m), supporting a prediction of significant fine-scale genetic structure (FSGS) within populations. To determine which of these two hypotheses is more likely to occur in nature, we measured inbreeding and quantified the spatial distribution of individuals and allozyme-based genotypes using spatial autocorrelation methods within four populations of the fern Cyrtomium falcatum in southern South Korea. Inbreeding levels were low, and all populations exhibited significant aggregation of individuals and strong FSGS. The present results support the second hypothesis, and the substantial FSGS in C. falcatum could reflect the unique features of most homosporous ferns (outcrossing mating systems that lead a majority of spores to occur at short distances and a very limited dispersal distance of male gametes). Although fern spores are physically analogous to orchid seeds, the intensity of FSGS exhibited in C. falcatum is four times stronger than that in 16 terrestrial orchid species.
authors: Department of Biology and the Research Institute of Natural Science, Gyeongsang National University, Jinju, South Korea.
authors: Mi Yoon
authors: MY
authors: Chung
authors: Myong Gi
authors: MG
authors: Chung
mesh_terms: D032491:Dryopteridaceae / Q000235:genetics*; D040342:Genetic Structures; D014644:Genetic Variation; D005843:Geography; D056910:Republic of Korea
keywords: Cyrtomium falcatum; allozymes; homosporous fern; mating system; spatial autocorrelation analysis; spatial demographic structure; spatial genetic structure; spore dispersal