Study On Ant-mediated Seed Dispersal Of Two Myrmecochorous Plants And Its Influencing Factors

Seed dispersal is a key process of plant growth and reproduction.Animals play an important role in this process for many plant species.As the most important seed disperser among invertebrates,ants are abundant and widely distributed in terrestrial ecosystems.They are of great significance to the seed dispersal of plants in ecology and evolution.Myrmecochory is widely found in various habitats in nature.Plants whose seeds can be dispersed by ants are Myrmecochorous plants.The typical characteristic of these plants is the presence of elaiosomes on the seeds.Elaiosome are rich in fatty acids and other nutrients,which can attract ants to disperse seeds.In the existing studies,there are few studies on the influence of other available foods,ant composition change and seed desiccating on ant dispersal,especially the saturation phenomenon of ant removal seed and its underlying influencing factors are often ignored.In this study,we use Corydalis giraldii Fedde(Papaveraceae)and Acalypha australis L.(Euphorbiaceae)to studied(1)the daily saturation amount of the seeds removed by ants and its relationship with the removal rate and dispersal distance.(2)the effects of other available foods and ant composition change on ant dispersal;And(3)the effect of seed desiccating on ant dispersal.The main findings are as follows:1.We studied the relationship between the daily saturation amount of the seeds of Corydalis giraldii Fedde and calypha australis L.dispersed by ants and the removal rate,the dispersal distance.The results showed that Paratrechina,Myrmica ruginodis and Camponotus are the common dispersers of seeds of Corydalis giraldii Fedde,while Paratrechina,Tetramorium and Temnothorax were the common dispersers of seeds of Acalypha australis L.The seed daily saturation amount of Corydalis giraldii Fedde dispersed by Paratrechina(3174.25±131.23 individuals)was significantly higher than that of Myrmica ruginodis(17±13.56 individuals)and Camponotus(1276.2±48.57 individuals)(P<0.05).The seed daily saturation amount of Acalypha australis L.dispersed by Paratrechina(18±5.24 individuals)was significantly higher than that of Tetramorium(12.2±3.03 individuals)and Temnothorax(3.4±0.55 individuals)(P<0.05).The daily saturation amount of the seeds of Corydalis giraldii Fedde(3174.25±131.23 individuals)dispersed by Paratrechina was significantly higher than Acalypha australis L.(12.2±3.03 individuals)(P<0.05).There is a positive correlation between the removal rates of Corydalis giraldii Fedde by Paratrechina(534.31±146.40 individuals/h),Myrmica ruginodis(4.73±2.15 individuals/h)and Camponotus(256.36±63.45 individuals/h)and the seeds daily saturation amount.The removal rates(4.17±1.17 individuals/h?2.29±1.11 individuals/h?1.00 individuals/h,respectively)and the dispersal distance(58.76±5.06 cm?38.02±6.61 cm?18.34±1.24 cm,respectively)of Paratrechina,Tetramorium and Temnothorax are positively correlated with the seeds daily saturation amount.These results suggest that different ants have different associational effect with the seeds.The associational effect between Paratrechina and the seeds of Corydalis giraldii Fedde is the greatest.The associational effect between ants and plant seeds affects ants' preference for seeds and may also affect plant benefits.The greater the associational effect,the greater the ants' preference for seeds and the greater the benefits to the plants.2.We studied the effects of alternative resources and the change of ant composition on the interaction between ants and the seeds of myrmecochorous.The results showed that different food supplementation significantly reduced the seed removal rates of Paratrechina and Camponotus.Among them,the addition of bread and meat(S×B×M)near the seeds had a more significant effect on the seed removal rates of ants(Paratrechina and Camponotus)than the addition of bread(S×B)or meat(SxM)alone(P<0.05),while the addition of bread only(S×B)and meat only(S×M)had no significant effect on the average seed removal rates of the ants(Paratrechina and Camponotus)(P>0.05).We found that there is no significant difference in the rate of seed removal in Myrmica ruginodis after adding food near the seeds(P>0.05).In this study,no matter whether food is added or not and what kind of food is added,the rate of seeds removal by Paratrechina is the highest.These results suggest that other alternative resources in the environment may inhibit the ant's seed preference,and the greater the variety of foods,the greater the effect.Compared with other ants,the interaction between Paratrechina and Corydalis giraldii Fedde is more close.Removed Paratrechina or removed Paratrechina and Myrmica Ruginodis both significantly increased the seed removal rate of Camponotus(P<0.05);While there is no significant difference in the seed removal rate of Camponotus between PC(removed Myrmica Ruginodis)and C(removed Paratrechina and Myrmica Ruginodis)(P>0.05).We found that there is no significant difference in the rate of seed removal in Camponotus after Myrmica Ruginodis is removed(P>0.05).These results suggest that ant composition change may affect the seed dispersal of the target ants.Paratrechina is the dominant competitor of Camponotus to the seed dispersal of Corydalis giraldii Fedde,while Myrmica Ruginodis has no significant effect on the seed dispersal of Camponotus.3.We studied the effects of different desiccated levels on seed dispersal of Corydalis giraldii Fedde.The results showed that the desiccated time of 8h,12h and 24h significantly reduced the rates and the distances of seed dispersal.(P<0.05).There is no significant difference in the removal rate and dispersal distance of the ants after seed desiccated for 4h(P>0.05).Seeds desiccated for 12 hours had greater effects on the dispersal distance of Myrmica ruginodis and Aphaenogaste smythiesii than those desiccated for 8 hours(P<0.05),but there is no significant difference in seed dispersal distance between the two treatments.Seeds desiccated for 24h have the greatest effect on seed dispersal.These results suggest that seed desiccated affects seed preference of ant and plant benefit.The elaiosome on the seeds have a certain freshness retention time,when the time exceeded will affect the ants to the seed dispersal service.The length of time that seeds remain attractive to ants varies between different ants.The results of this study indicate that the associational effect between ants and plant seeds affects ants' preference for seeds and may also affect plant benefits.Other alternative resources in the environment,ant composition change and seed desiccated can affect ant-plant interactions.These contribute to the understanding of the mutualistic relationship between ants and plants.