Calcicolous plants colonize limed mires after long‐distance dispersal

Abstract

AbstractAimDispersal range is a key factor for understanding species' persistence in dynamic landscapes. However, dispersal, especially over long distances, is inherently difficult to study. Making use of a unique system of anthropogenically disturbed, geographically isolated mires, we assessed dispersal ranges for a group of plants restricted to wet calcareous conditions via empirical studies of colonization patterns. We hypothesized that more species would have colonized the less isolated mires and that colonization frequencies would be related to traits influencing propagule pressure.LocationSweden.TaxonCalcicolous vascular plants and bryophytes.MethodsThe study system consisted of 52 acidic mires that had acquired a high pH through active liming by the Swedish government during the past two decades. These conditions killed off mat‐forming peat mosses, rendering the mires open to colonization by other species. In each mire, we recorded the presence of rich fen plant species typically found in high pH wet soils throughout the country. We used citizen science‐collected records of occurrences of obligate‐rich fen species surrounding each mire to examine the likely dispersal distances that were involved in creating the colonization patterns.ResultsA lower proportion of vascular plants than bryophytes from their respective species pools colonized the limed mires (27% vs. 67%, p = .001). The number of colonized rich fen species per site was 0–6 for vascular plants and 10–31 for bryophytes, and was positively related to potential diaspore sources >20 km from the mires (p = .026 and p = .012, respectively). The proportion of colonized mires was positively related to the species' regional frequency, but not with their diaspores' terminal velocity.Main conclusionsMany bryophyte species can effectively disperse over long distances (tens of kilometres) and variation among species in total diaspore production seems to be an important regulator of colonization across landscapes, for both vascular plants and bryophytes, in communities that are open to colonization.