Variation And Phenotypic Plasticity Of Life History Traits Of Spartina Alterniflora Populations Along East Coast Of China

Genetic differentiation and phenotypic plasticity are two major strategies of biological adaptation to varying environments. The heterogeneity is ubiquitous in all types of habitats where alien species arrive. To succeed in settling in nonnative environments, exotic species must rapidly adapt themselves to the environmentally diverse areas. Therefore, genetic differentiation and/or phenotypic plasticity may play an important role in the expanding process.Spartina alterniflora is a rhizomatous perennial grass native to the east coast of North America, which has been considered as a global invasive grass as it threatens the coastal ecosystems of North America (the west coast), Europe, North Island of New Zealand and China. It has been spreading in the coastal ecosystems in the east coast of China since it was originally introduced in 1979. S. alterniflora was recognized as one of the 16 most harmful alien species in China in 2003.To investigate the variation in the life-history traits and phenotypic plasticity of S. alterniflora in China, I collected samples of ten populations from the east coast of China along a latitudinal gradient from Guangdong (22°N) to Tianjing (39°N). I grew the plants singly in pots placed in an outdoor common garden under either low or high water level to explore its plastic responses to a simulated elevational variation in the field.The results demonstrated, considerable variation among populations existed in 12 of 18 traits measured. In particular, the days to full blossom declined as the latitude rised. Meanwhile, the other 11 traits showed considerable variations, though not correlated with latitude. Furthermore, the relative growth rate of height (RGR_H) increased with increasing latitude. Additionally, 9 of 18 traits showed remarkable plasticity in response to different water levels. S. alterniflora at high water level was more prolific and produced the first ramets earlier, the biomass allocated to stems, shields and ramets also varied between the two water levels.The results suggested that the Chinese populations of S. alterniflora might have experienced genetic differentiation, and have great phenotypic plasticity. The former might have facilitated its rapid range expansion on a regional scale, and the latter might have played an important role in local adaptations to the habitats along an elevational gradient. Hence, the successful invasion of S. alterniflora in China might have resulted from a combination of genetic differentiation and phenotypic plasticity.