Population stage structure of three congeneric Dryopteris species in Estonia

Abstract

There are three congeneric fern species in Estonia that show similar morphology and ecology, but whose regional distribution is different-Dryopteris carthusiana is common, D. expansa is distributed in scattered localities, and D. dilatata is rare. We studied D. carthusiana, D. dilatata, and D. expansa in localities where all three fern species co-occur in Estonia. Our aim was to compare the population stage structure of the three species and to observe whether their population structure fluctuates differently in different sites in different years. We observed an unfavourable condition of D. expansa in one site (Sääre), which we interpreted as a possible result of competitive pressure from bryophytes. Also, we observed a predomination of premature stages of D. dilatata in two sites (Jäneda, Õngu), indicating the dynamic status of these populations. Because of a more westerly distribution of this species in Estonia compared to the other two, one may hypothesize that D. dilatata is able to expand its range due to climate warming.