Biological invasion is becoming one of most serious environmental problems in the 21^st century. Flaveria bidentis, an exotic plant with the strong invasiveness from South America, has spread over more than 92 counties of Hebei Province and expanded to Tianjin, Shandong, Henan Province in China as well. The wise management on the exotic species is pivotal for the balance of ecosystem and the maintenance of biodiversity. There are many challenges for classical biological control, such as host specificity, biosafety risk, and appropriate applications as well as efficiency assessment. This study aims to mimic the effects of herbivory damage on plant growth and reproduction in invaded habitats and thus to investigate whether herbivory treatment could be used as an effective measure to manage F. bidentis.
A field experiment was carried out to clarify the effects of simulated herbivory damage on the growth, reproduction and related physiological characteristics of F. bidentis. We clipped leaves with scissor to simulate different level damage by folivores and removed apical meristems to simulate apical mortality caused by stem borers. Five treatments were designed,three levels of leaf removal (1/4, 1/2, and 3/4), apical meristem removal and the undamaged control. Each treatment included 45 replications (individual plant), and each plant is marked by a nameplate.
Compared with the control, the overcompensation effect was observed under low level damage and apical removal treatments with increased total biomass, root biomass, stem biomass, plant height, branch numbers, flower bud numbers, net photosynthetic (Pn) and water use efficiency (WUE), while,these parameters were only reduced by severe damage level (3/4) in our study. Initial fluorescence yield (F₀) under three leaf damage treatments was significantly higher than that in other treatments, whereas the maximum photochemical efficiency of photosystem Ⅱ (Fv/Fm) and potential activity of photosystem Ⅱ (Fv/F₀) were significantly suppressed. Higher phenotypic plasticity were observed in biomass related parameters, indicating these parameters of F. bidentis have high herbivore tolerance, which might make an important acclimation under herbivores regimes for this invasive species.
These results suggested that natural enemies may have little impact on fecundity of F. bidentis. In practice, more swift management strategy such as clipping, plant replacement and integrated control measure is required to prevent the reproduction of this weed.