Spatial distribution of epixylic hepatics in relation to substrate in a boreal old-growth forest

The spatial distribution of three epixylic hepatics, Anastrophyllum hellerianum, Lophozia silvicola and L. longiflora, was analyzed in a boreal old-growth forest in southern Finland, by applying Ripley's K-function and its modification (L(r)). The studied species inhabit coarse woody debris (CWD), a clearly delimited, patchily distributed substrate of varying quality depending on the tree species, patch size and stage of decay. The three hepatic species differ in substrate specificity and in reproductive mode, whether prevailingly sexual or asexual. The combination of substrate specificity and the frequency of sexual and asexual reproduction leads to differing spatial patterns in each species. Our results support the hypothesis that randomness in distribution is related to frequent spore production, since spores are considered to be the means of distance-dispersal, while an aggregated pattern is an outcome of local dispersal by asexual propagules. Substrate specificity combined with the frequency of spore production influences the scale of aggregation in species relying primarily on asexual reproduction and local dispersal.