Effects of Japanese marten (Martes melampus) gut passage on germination of Actinidia arguta (Actinidiaceae): Implications for seed dispersal

摘要

To evaluate the effect of Japanese martens (Martes melampus) gutpassage on seed germination, a qualitative component of seed dispersal effectiveness, we fed the seeds of a liana, Actinidia arguta, to captive animals and compared the germination ratios between ingested seeds and seeds with their pulp removed artificially, and among seeds with pulp under different conditions. Field experiments were conducted to test the effects of light level and pulp on germination. Ingested A. arguta seeds showed a significantly higher germination ratio than those subjected to other treatments, and seeds without pulp showed higher germination ratio than those with pulp, suggesting that ingestion by martens is beneficial for pulp removal. Mean number of days until germination did not differ across treatments, and martens' ingestion did not provide a significant competitive advantage over control seeds. Finally, the light level had no effect on germination ratio. Actinidia arguta grows quickly and has a higher density than that of other plant species at the forest edge, where the Japanese martens prefer to defecate for their territorial marking. The martens provide two positive effects on early stage of A. arguta fitness: transportation of intact seeds to suitable sites and stimulation of germination through pulp removal. They may also be directed dispersal agents for this liana species. Relative importance of the martens on the dispersal effectiveness of A. arguta, therefore, should be much greater than that of sympatric frugivores.