Geographical variation in vegetative growth and sexual reproduction of the invasive Spartina alterniflora in China

We studied patterns in vegetative growth and sexual reproduction of introduced S. alterniflora at 22 sites at 11 geographic locations over a latitudinal gradient of ~2000 km from Tanggu (39.05 °N, high latitude) to Leizhou (20.90 °N, low latitude) in China. We further evaluated the basis of phenotypic differences by growing plants from across the range in a common garden for 2 growing seasons. We found distinct latitudinal clines in plant height, shoot density, and sexual reproduction across latitude. Some traits exhibited linear relationships with latitude; others exhibited hump-shaped relationships. We identified correlations between plant traits and abiotic conditions such as mean annual temperature, growing degree days, tidal range, and soil nitrogen content. However, geographic variation in all but one trait disappeared in the common garden, indicating that variation largely due to phenotypic plasticity. Only a slight tendency for latitudinal variation in seed set persisted for two years in the common garden, suggesting that plants may be evolving genetic clines for this trait. Note that these data were collected as part of a National Natural Science Foundation of China (NSFC) funded study led by Yihui Zhang in collaboration with GCE-LTER.