Abstract
Despite the large number of comparative studies on species with different distribution and abundance, no clear general pattern of attributes explaining species' rarity has yet been found. The relationship between different life-history traits of a species and abundance tend to be conditional and context dependent. We were interested in whether the local relative population density of three fern species in Estonia is related to post-emergence growth of their young sporophytes, i.e., that the locally abundant species. D. carthusiana, has the highest vegetative growth in its first growth periods and the two less abundant species, D. dilatata and D. expansa, have lower. We were also interested in differences between generative traits of young sporophytes of three species, specifically in the number of spores. We grew the species in a garden experiment for two vegetation periods, 2004-2005, until the first sporulation. The relative population density of the three Dryopteris species was related to the relative post-emergence growth of the species. The most abundant species D. carthusiana, exhibited the highest values of vegetative growth parameters in the first growth period. The less abundant D. dilatata and D. expanse both had shorter fronds, shorter intensive growth periods and lower leaf elongation rates. Diyopteris dilatata had a different vegetative growth strategy compared to the other two species; it differed in timing of intensive growth of frond length and increase of frond number and had the lowest values of generative parameters among the three species.