Dispersal ability is of great importance for plants, which commonly occupy spatially and temporally limited substrate patches. Mixed reproductive strategies with abundant diaspore production are favoured in a heterogeneous landscape to ensure successful colonisation at different distances. In bryophytes, long-distance dispersal has been thought to take place primarily by spores, while asexual propagules are important in local dispersal and in the maintenance of colonies. In the present study, we investigated the dispersal potential of two equally sized propagules, sexually formed spores and asexually produced gemmae in the dioecious, epixylic hepatic, Anastrophyllum hellerianum, which inhabits spatially and temporally limited substrate patches. We trapped propagules at different distances (0-10 m) and directions from the source colonies in two experiments: one in a natural habitat within a forest and another involving an artificial set-up in an open habitat. Spore dispersal showed only slight distance dependence both in the open and the forest habitats, presumably as a consequence of wind affecting the dispersal pattern. Gemma dispersal was more strongly distance-dependent in the open habitat than in the forest sites. Considerably more gemmae were deposited during rainy than dry periods, possibly because of the effect of rain drops on gemma release. However, weather conditions had no effect on the dispersal patterns of spores or gemmae. In A. hellerianum, the combination of occasional spore production and practically continuous, massive gemma production facilitates dispersal both on local scale and over long distances. Unlike previously assumed, not only spores but also the asexual propagules may contribute to longdistance dispersal, thus allowing considerable gene flow at the landscape level.

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We investigated substratum preference, niche breadth and niche overlap in relation to selected substratum variables in three epixylic hepatics: Anastrophyllum hellerianum, Lophozia silvicola and L. longiflora. The species studied inhabit coarse woody debris, which is a patchily distributed substratum with varying qualities as determined by tree species, patch size, bark cover and stage of wood decay. The three hepatic species differ in substratum specificity and reproductive mode, being either prevailingly sexual or asexual. Although the species possessed differences in substratum preference, between-species niche overlap values were high. All three species showed wide ecological amplitude in relation to coarse woody debris quality. Our results suggest that the epixylic hepatics A. hellerianum, L. silvicola and L. longiflora exhibit opportunistic strategies in relation to substratum quality, thus maximizing survival on a temporally and patchily distributed substratum.