Dispersal, recruitment and site occupancy of grassland plants in fragmented habitats

We examined adhesive seed dispersal. recruitment and sire occupancy of 17 p lant species characteristic of semi-natural grasslands. The main objectives were to examine different aspects of dispersal: the potential distance of seed transport: the likelihood of recruitment at putative "suitable sites" along road verges; the spatial (realised) patterns of occurrence along road verges (occupancy); and associations among these aspects and seed size. Ad hesive dispersal capacity was investigated experimentally using cattle. Rec ruitment was investigated by seed sowing experiments. Occupancy was recorde d in two regional surveys. Results suggested that adhesive dispersal may be an effective mode of seed transport. even for species which lack special " adhesive" structures, such as hooks or hairs. Fifteen of the 17 species suc cessfully recruited at the experimental gaps and adjacent grassy areas. Dis turbance promoted seedling recruitment. Seedling emergence was negatively a ssociated with adhesive dispersal capacity. Sparial (occupancy) patterns a: ere not related to recruitment Features or dispersal capacity. There is som e support for a trade-off between adhesive dispersal capacity and recruitme nt ability, but no support for a trade-off between adhesive dispersal capac ity and ability to withstand competition during recruitment. The results ar e discussed in the context of species distribution and persistence in fragm ented landscapes. We suggest that adhesive dispersal has been underestimate d as a mechanism of seed transport, but that adhesive dispersal capacity pe r se is not the main factor determining species occupancies in Fragmented g rasslands.