Multiple limitations to the persistence of Trollius europaeus in a fragmented agricultural landscape in the context of metapopulation theory

Abstract

The knowledge about determinants of species survival is fundamental in conservation. Beyond determinants affecting local population survival, metapopulation theory emphasises the importance of processes operating on larger spatial scales (e.g. dispersal). We studied dispersal capacity and requirements for seedling recruitment of the threatened fen grassland species Trollius europaeus in order to assess the species’ ability to persist under the current land use conditions in the study region, north-east Germany. We used a seed sowing experiment and simulated endozoochorous and hydrochorous dispersal in a field and a laboratory experiment. Germination success reflected the experimental reduction of vegetation complexity, but the germination and recruitment rate was overall low. Survival was followed 2008–2011 and was best on plots with an intact moss layer. Mollusc exclusion displayed no significant effect. Endozoochorous dispersal is possible, however, in only minor quantities. Hydrochorous dispersal is very limited and negligible for connecting distant patches. We found evidence for microsite limitation, remnant population dynamics and the existence of unoccupied but suitable habitat patches available for colonization in our study region. However, (re-)colonization events are probably very rare due to dispersal limitation stressing the need for artificial seed transfer within the scope of restoration projects. Therefore, large quantities of seed material should be used in combination with mowing and thorough litter removal but leaving the moss layer intact. Management should be continued for longer than just the introduction year. Our study contributes to the understanding of species dynamics in fragmented landscapes. In particular, it contributes to the conservation of T. europaeus as an indicator of species-rich fen meadows in its Central European range.