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Exotic plant invades threaten natural ecosystems and human economic interests.Biological control should be the preferred control strategy to eradicate invasive plants and restore the natural ecosystems.Cuscuta spp.are holoparasitic plants,which absorb nutrients and water from the host and inhibit host plant growth.Cuscuta spp.have been found to help restore native communities by inhibiting the growth of invasive plants,reducing the cover of invasive plants and increasing community diversity and have been demonstrated to be potential biological control agents for invasive plants.Alternanthera philoxeroides,native to South America,is a noxious invasive plant throughout the world and is widely distributed in China.Mechanical,chemical and biological methods have been used to control the weed but to limited success.In the field,we find that A.philoxeroides is naturally parasitized by C.australis.We compared the growth of A.philoxeroides and native community diversity in field plots where C.australis was present compared to control plots where C.australis was absent.Parasitism by C.australis caused A.philoxeroides to allocate resources to belowground structures,significantly decreasing the stem:mass ratio and significantly increasing root:mass and root:shoot ratios.Parasitism by C.australis also tended to reduce leaf biomass,stem biomass,root biomass and total biomass,height and percent cover of A.philoxeroides,although these effects were not statistically significant.C.australis also increased diversity.In the plots without C.austraslis,we found 14 plant species belonging to 14 genera in 10 families.In the community dominated by A.philoxeroides parasitized by C.australis,we observed 29 plant species belonging to 27 genera in 16 families,68% of which can be parasitized by C.australis.Parasitism by C.australis significantly increased species richness and tended to increase the Simpson diversity index,Shannon-Wiener diversity index,McIntosh diversity index and uniformity of the community.Parasitism of C.australis significantly decreased the abundance of A.philoxeroides in the community and decreased the cover and height of A.philoxeroides although these effects were not statistically significant.Parasitism of C.australis significantly decreased the relative cover,relative height,relative abundance and thus the important value of A.philoxeroides in the community.The results indicated that parasitism of C.australis could inhibit the growth of A.philoxeroides and increase community diversity,facilitating the restoration of native communities. |
