Abstract:

Spartina alterniflora, native to North America, is invasive in salt marshes worldwide. Its geographic distribution in China has expanded to include most eastern coastal areas since it was introduced in 1970s. Genetic differentiation and phenotypic plasticity are two major strategies in adaptation to varying environments. To investigate the mechanisms of the range expansion of S. alterniflora in China, we collected samples from ten populations on the east coast of China along a latitudinal gradient from Guangdong (22°N) to Tianjin (39°N). We grew plants singly in pots placed in an outdoor garden under either low or high water levels to explore plastic responses to varying elevation in the field. Twelve of 17 traits measured demonstrated considerable variation among populations. In particular, mean date of blossoms and the relative growth rate of height (RGR_H) showed clinal variation with latitude. Our results suggested that Chinese populations of S. alterniflora might have experienced genetic differentiation. Furthermore, 9 of 17 traits showed remarkable plasticity in response to different water levels. S. alterniflora at high water level was more prolific and produced its first ramet earlier. Therefore, the successful invasion of S. alterniflora in China might have resulted from both genetic differentiation and 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 habitats along an elevational gradient.

Key words: phenotypic plasticity, Spartina alterniflora, water level, genetic differentiation