[Effects of above- and below-ground herbivore interactions on interspecific relationship between the invasive plant and its native congener ].

Biological invasion is a major threat to global biodiversity. The relative interspecific competition abilities of invasive species compared to those native species determine their invasion success. In this study, we examined the effects of the specialist leaf beetle and the nematode on the growth and interspecific relationship between the invasive plant and its native congener Compared without herbivory, nematode herbivory alone significantly reduced shoot height of by 28.1%, but conversely significantly increased the shoot height of by 52.8% and aboveground biomass of by 63.7%. Beetle herbivory alone significantly reduced shoot height of by 40.7%, but did not affect that of . The combination of beetle and nematode herbivory significantly reduced shoot height of by 35.3% as well as the belowground biomass of by 62.2%, but significantly increased the aboveground biomass of by 69.1%. Herbivore stress did not affect stem diameter, branch number, and root length of both species. The relative neighbor effect index (RNE) of the two species without herbivory were positive, and the RNE value of was 21.3% higher than that of . However, the RNE values of were negative under all above- and below-ground herbivory treatments. The RNE values of were positive under the beetle or the nematode herbivory alone and negative under the beetle + nematode herbivory combination. These results indicated that above- and below-ground herbivore interactions could change the interspecific relationship between the two species, and in turn might accelerate the invasion of .