Effects Of Division Of Labor On The Invasiveness Of Alternantheraphiloxeroides(Mart.) Griseb.

Alien invasive species can modify the stability and functioning of local communities,and displace native plants with the consequent loss of biodiversity.Most of the successfully invaded plants are clonal plants with strong reproductive ability,however,the mechanism of the characteristics of clonal plants for their successful invasion has not been clarified.The clonal division of labor of A.philoxeroides has less research on its successful invasion,especially in its different types and the comparison with native species.In a green house,we select A.philoxeroides to study the developmentally-programmed and environmental induced division of labor,the difference between ecotypes and comparison between native and coexistence species.We aim to explore the effect of division of labor in the invasive progress of A.philoxeroides and enrich the theory of clonal characteristics of invasive clonal plant and provide a theoretical basis for the prevention of A.philoxeroides.The main results of this paper are as follows:(1)To simulate the homogeneous and heterogeneous habitats which plants growing in natural conditions,we sheared the apical or basal ramets and provide high or low nutrient for homogeneous and heterogeneous environment.The performance in homogeneous with high nutrient showed higher performance than in low nutrient,the connected and severed ramet showed significant difference in high light treatment.In high light and high nutrient treatment,connected basal and apical ramets showed a significant specialization for resource that basal ramet which devoted more biomass on root mass and apical ramets acquired more shoot mass and the mass allocatiion is benefical for growth.The LH-HL treatment in heterogeneous environment showed a significant biomass allocation difference which the basal ramet have a high root to shoot ratio and the apical show a low root to shoot ratio.Ramet connected increased the overall performance of A.philoxeroides which reflecting the contribution of clonal division of labor to plant spread.(2)Experiments were conducted in heterogeneous environment with aquatic and terrestrial ecotypes of A.philoxeroides,severing the ramets to hinder division of labor.The results showed that the severing treatment significantly reduced the performance of the two ecotypes of A.philoxeroides,and the connected ramets all show a morphological division of labor.Terrestrial ecotypes show a more significant ability for division of labor with a higher root to shoot ratio in basal ramets.Stolon connection is benefical for clone growth and terrestrial ecotypes has a better adaptability to heterogeneous habitat than aquatic ecotypes.(3)The invasive species A.philoxeroides,native species A.sessilis,and the coexisting species L.peploides were selected and maintained at the basal and apical ramet under the condition of heterogeneous resources.The results showed that the ramets of invasive species in the basal ramets had higher performance than the native and co-existing species,and three species at the apical part had better growth performance.Invasive species showed significant differences between basal and apical ramets in total mass.Ramets severed significant decreased the root to shoot ratio of invasive species and the native A.sessilis showed an adverse changes.A.philoxeroides had the higest cost-benefit than A.sessilis and L.peploides in basal ramets,and there was no significant difference in cost-benefit of apical ramets among the three species.(4)Two densities of L.peploides population were constructed to be invasived by the apical part which keep connetced or severed with basal part of A.philoxeroides to study the effect of division of labor in the invasive progress of alien plants.The results showed that stolon connected decreased the performance of basal ramets and increased the growth of apical parts under different density of L.peploides population.A.philoxeroides had a lower performance in high density and a significant difference in root to shoot ratio between two density of L.peploides population.Invasive species showed a higer cost-bebefit in high density than in low density and the exsistence of A.philoxeroides decreased the growth of L.peploides population,especially in high density.Stolon severed increase the cost-benefit of high density of L.peploides population,which indicated that an adverse effect of A.philoxeroides on L.peploides growth.