Abstract: Leaf functional traits reveal the ecological strategies of plants and affect growth and distribution. Variation in leaf traits was usually documented across species in terrestrial ecosystems, studying in wetlands can advance the understanding about leaf trait variation along environmental gradients. Intraspecific study contributes to explore trait variation and underlying mechanism. Marine coastal wetlands have become hot spots for studying trait variation. Invasive Spartina alterniflora distributed along China’s coastline, is an ideal species for studying leaf traits variation. We determined geographical variation and abiotic drivers in six leaf functional traits, and explored the roles of phenotypic plasticity and genetic differentiation through a 2-year common garden experiment. We detected relationships between leaf traits and growth performance in field and common garden. All leaf traits exhibited significant geographical variation, which were affected by both climatic and sedimentary variables. Common garden experiment exhibited the trait-dependent response, different leaf traits showed various degrees of plastic response or genetic differentiation. Variation in leaf size, leaf thickness, and specific leaf area displayed genetic differentiation, while variation in leaf density and leaf dry matter content exhibited plastic response. Leaf size and thickness positively correlated with growth performance in field and common garden. Our study advances the understanding about leaf trait variation in the terrestrial ecosystems. Multiple abiotic variables shape the latitudinal patterns in leaf traits. Resource acquisition at high latitudes in the northern hemisphere contributes to great growth performance of S. alterniflora, which might promote expansion northward, whereas the resource conservation at low latitudes might hinder expansion southward.

Key words: Adaptive mechanism, Common garden, Growth, Latitudinal gradient, Leaf traits, Spartina alterniflora