Abstract: Transgenerational plasticity (or transgenerational effect) is believed to play a potential role in promoting the spread and successful establishment of invasive plant species. However, the differences in transgenerational plasticity between invasive and native clonal plants are less understood. In a common garden experiment, maternal ramets of the invasive species Wedelia trilobata and its native congener Wedelia chinensis were grown under either well-watered or drought-stressed conditions. After 10 weeks, offspring ramets from both treatments were transplanted into a uniform drought-stress environment. Morphological traits, photosynthetic parameters, and biomass allocation strategies of the offspring were measured to address two questions: (1) Does maternal drought stress enhance offspring performance under drought through transgenerational effects? (2) Are there differences in transgenerational plasticity between the two species? Our results showed that both species exhibited significant transgenerational effects, but with substantial differences in the response magnitude and regulatory scope of specific traits. Offspring of drought-stressed W. trilobata achieved higher total biomass accumulation by reducing specific leaf area, specific root length, and specific root volume, while increasing root surface area, stomatal conductance (G_s), maximum quantum yield of photosystem Ⅱ (F_v/F_m), actual photochemical efficiency (Φ_PSⅡ), and photochemical quenching (qP). Although maternal drought stress altered root morphology and leaf photosynthetic performance in W. chinensis offspring, these changes did not translate into higher biomass production. This study revealed that maternal drought stress can confer increased drought tolerance to offspring via transgenerational plasticity in both Wedelia species. W. trilobata displayed stronger transgenerational plasticity, which may underpin its superior environmental adaptability and invasion potential.

Key words: drought stress, transgenerational effect, clonal plant, plant invasion, morphological trait, photosynthetic trait