The distribution of Spartina alterniflora across a wide latitudinal gradient in its native (USA, ~27-45o N) and invasive (China, ~19-41o N) ranges provides a model system to study evolution and invasion. We compared native and invasive accessions of S. alterniflora, measuring individual traits (plant height, seed production, seed set) and population characteristics (shoot density, aboveground biomass/m2, percentage of flowering culms) in the field for 26 populations of S. alterniflora at 26 geographic locations (16 in the native range, and 10 in the invasive range). We grew seeds from these populations in a greenhouse common garden in China to compared plant growth and reproductive traits in a common environment.
Results/Conclusions
While in the field multiple traits (plant height, shoot density, aboveground biomass/m2, and percentage of flowering culms) of S. alterniflora have similar latitudinal patterns between the native and invasive ranges, seed production and seed set differ, with higher values at higher latitudes in China. Moreover, we found evidence for increased plant vigor in the introduced ranges: plants were taller, with higher aboveground biomass/m2 than in the native range. Most interestingly, the invasive populations set more seed and more viable seed set than North American S. alterniflora both in the field and in common garden, suggesting evolution of greater sexual reproduction in the invasive populations in China.