Seed biology of Mikania micrantha in Viti Levu, Fiji

Summary Mikania micrantha (mile‐a‐minute) reproduces both by seed and vegetatively. A study to determine the possible pollinators, seed production rates, temperature and salinity limitations to germination and its seedbank size and persistence was conducted in Viti Levu, Fiji. Representatives of the Diptera had the greatest percentage of all floral visits (38%), followed by Hymenoptera (34%) and Lepidoptera (27%), while the honeybee was the most recurring visitor (18% of all visits). Flower heads (capitula) within the inflorescence commonly formed four viable seeds, resulting in 60 820 filled seed being produced per m2. However, the seedbanks formed were not massive (600 seed m−2) and they were moderately persistent (T50: 1–3 years). Seed germination from both high and moderate rainfall regions occurred rapidly, under a wide range of temperature regimes, with no primary dormancy being observed. This study indicates that the seed reproductive success of M. micrantha in the two rainfall regions of Fiji is due to a number of factors, including the production of large numbers of flowers, successful pollination by local insects and the subsequent production of a large number of viable seeds. These seeds have high viability, no dormancy and are capable of forming small‐to‐medium seedbanks that are moderately long‐lived. In addition, seeds can germinate under a wide range of temperature and salinity conditions. This knowledge on seed production, biology, longevity and salt tolerance is vital in the development of management plans of M. micrantha in Fiji.