Abstract:

Aims Spartina anglica, a world-wide invasive species introduced from Europe in 1963, rapidly increased in coastal China before the 1990s and thereafter drastically declined. Researchers hypothesized that small initial clone numbers might be responsible for the decline. We investigate the effect of different initial clone numbers on morphological plasticity and biomass allocation of S. anglica.
Methods From May to November 2005, field experiments were conducted in S. anglica vegetation located along the coast of the Yellow Sea (32°34'-34°28' N, 119°48'-120°56' E). We set up three treatments with one, three, and five initial clones. For each plant, we measured height, stem diameter, leaf thickness, leaf area, number of leaves, spacer length and branching intensity as morphological parameters and number of ramets, rhizomes and rhizome nodes and total length of rhizomes as growth traits. We also analyzed biomass accumulation, allocation and allometric growth of S. anglica.
Important findings With greater initial clone number, branching intensity, total biomass, above-ground biomass, below-ground and rhizome biomass increased significantly, but initial clone number did not affect root biomass and spacer length. Plants in multi-clone treatments tended to allocate more resource to rhizomes, while those in the single-clone treatment tended to allocate more resource to roots. Results indicated that S. anglica plants with multiple clones had more effective asexual reproduction than plants with a single clone. Because most environments likely were invaded by a single clone and then added additional clones, we hypothesize that the main reproduction strategy of S. anglica has changed from sexual to asexual reproduction, which may account for the population dieback since the 1990s in China.

Key words: morphological plasticity, Spartina anglica, clone number, biomass allocation, asexual reproduction