Different factors govern the performance of three closely related and ecologically similar Dryopteris species with contrastingly different abundance in a transplant experiment

Abstract

We conducted a transplant experiment to address aspects of the contrasting ecological performance of three forest ferns with similar habitat preferences: Dryopteris carthusiana (Vill.) H.P. Fuchs (common in Estonia), Dryopteris expansa (C. Presl) Fraser-Jenkins & Jermy (less common in Estonia), and Dryopteris dilatata (Hoffm.) A. Gray (rare in Estonia). Sporophytes of the three species were reciprocally planted in pots of soil in three neighbouring sites, where only (i) the most common, (ii) two more common, or (Hi) all three grow naturally. The experimental design allowed the grouping of the possible limiting factors: light-related, soil-related, and effect of locale (factors associated with a particular locality but not directly related to light or soil). D. expansa (less common) was vulnerable to edaphic conditions: its performance was significantly poorer in soil from the site where it was naturally absent. D. dilatata (rare) was unaffected by soil conditions, indicating that either limited dispersal or effect of locale is responsible for its rarity. Our results indicate that even for taxonomically close and ecologically similar species, the forces that shape plants' distribution and abundance can be markedly different.