Effects Of Clonal Division Of Labor On The Invasive Plant Alternantheraphiloxeroides (Mart.) Griseb. And Its Related Species

Plant invasion seriously affects the diversity of global and regional ecosystems and the stability of the national economy,and clonal plants are the main groups of these alien invasive plants.The successful invasion of cloned plants is closely related to their unique clonal life history traits,and the intra-clonal division of labor mediated by clonal integration is the most important one of these clonal traits.Alternanthera philoxeroides is one of the most harmful clonal plants among the exotic plants invading China.However,there are few studies on its clonal division of labor,which only focuses on its own clonal division of labor under heterogeneous conditions.There is a lack of comparative studies with other species,especially the related species of the genus Alternanthera,so it does not directly reveal the contribution of clonal division of labor to its invasion.This paper takes the invasive species A.philoxeroides as the main research objects,and selects the native plant of the same genus Alternanthera sessilis and the exotic non-invasive plant Alternanthera bettzickiana as the comparative research object,based on the method of greenhouse control experiment and the principle of comparative ecology.The effects and differences of clonal division of labor on A.philoxeroides and its related plants were studied.With the model clone plant A.philoxeroides as the representative,the contribution of clonal division of labor to invasive plants and its mechanism were revealed.The main results of this paper are as follows:(1)For the purpose of verifying the division of labor of the two types of clones,two experiments of homogeneous and heterogeneous resources were set up to control nutrition and light conditions.The clonal fragments of invasive species like A.philoxeroides,non-invasive species A.bettzickiana and native species A.sessilis were cut off(blocking division of labor)and maintaining connection(allowing division of labor).The purpose of this study is to explore the existence and ability of clonal division of labor among three species.The results showed that under the condition of heterogeneous resources,under the treatment of low light and high nutrients at the base,the underground part of the basal ramet and the aboveground part of the apical ramet of A.philoxeroides were functionally specialized,and the root-shoot ratio of the connected apical ramet growing in high light and low nutrient was significantly lower than that of the cut-off tip ramet,and the root-shoot ratio of the connected basal ramet growing in low light and high nutrient was significantly higher than that of the cut-off basal ramet.The connected apical ramet put more biomass into the aboveground structure,resulting in a stronger ability of cloning and reproduction,significantly increasing the biomass of the whole clone fragment,and realizing the division of labor of the whole clone ramet.A.bettzickiana and A.sessilis only had the functional specialization of the underground part of the basal ramet,and the stolon connection significantly increased the total biomass of the whole clone fragment of A.bettzickiana.The underground part of the basal ramet of A.philoxeroides connected by stolon was functionally specialized under the treatment of homogeneous high light,low light and high nutrient.The total biomass of the whole clone of A.philoxeroides was significantly increased.At the same time,functional specialization also occurred in the underground part of the basal ramet of A.bettzickiana under the treatment of homogeneous high light and low nutrient,and the underground part of the basal ramet of A.sessilis under the treatment of homogeneous low light and high nutrient,which supplied more resources to the underground structure of the basal part,resulting in a larger root-shoot ratio.(2)We cut the leaves of the invasive A.philoxeroides,A.bettzickiana and A.sessilis to simulate the feeding in the natural habitat,through the integration experiments under the two states of connection and cut-off,the purpose of this study was to explore the effect of clonal labor division of A.philoxeroides and its related species in defoliated habitat.The results showed that under the condition of control treatment and moderate defoliation treatment,there was no obvious clonal division of labor among A.philoxeroides,but clonal integration occurred among connecting ramets at different levels of defoliation.The total biomass of the whole clone fragment in the control group was significantly increased,and the division of labor occurred in the basal ramet of A.philoxeroides under the experimental condition of severe defoliation.The results showed that when the stolon connection was cut off,the root-shoot ratio of the basal part of A.philoxeroides was significantly increased,the biomass of the basal ramet and the total biomass of the whole clone were increased.Under the condition of control treatment and moderate defoliation treatment,the basal ramets of A.bettzickiana and A.sessilis were specialized,which was reflected in that when the stolon connection was cut off,the root-shoot ratio of the basal part and the total biomass of the whole clone of A.bettzickiana in the control group were significantly increased,but the division of labor did not occur under the severe defoliation treatment.(3)the invasive species A.philoxeroides,A.bettzickiana and A.sessilis were selected as the main research object to construct different competitive communities of A.philoxeroides and its related species.At the same time,the connected ramets of A.philoxeroides were kept connected or cut off,and the direct effects of clonal division of labor on A.philoxeroides under different competitive conditions and the indirect effects on their related species were compared.The results showed that under the condition of control treatment and competition with A.sessilis(AS+AP+AS)and A.bettzickiana(AB+AP+AB),the basal ramet connected by A.philoxeroides had obvious division of labor,resulting in a larger root to shoot ratio and significantly increased the underground biomass of the basal ramet.When there is no interspecific competition,the first ramet of A.philoxeroides gives priority to the growth of the aboveground part,and the basal ramet puts more biomass into the underground part,thus realizing the division of labor.When there was interspecific competition with A.bettzickiana and A.sessilis,although the connected alternanthera philoxeroides has the functional specialization of the basal ramet,it increases the biomass of the basal ramet of alternanthera philoxeroides.,the root-shoot ratio of the basal ramet of A.philoxeroides was significantly lower than that of the control group,and the ability of division of labor was significantly decreased.At the same time,the functional specialization of A.philoxeroides significantly affected the growth of A.bettzickiana and A.sessilis,and the inhibitory effect on A.bettzickiana was more obvious.