Effect Of Exotic Introduced Plants Azadirachta Indica And Moringa Oleifera On Pollination Network Of Dry-hot Valley In Honghe Area

Dry-hot valley is area with low plant-cover and fragile ecological environment,but plant yield of seeds and fruit could be great due to richness of sunshine and heat under circumstance of enough water supplies.Thus,agro-forestry scale has been quickly developed by cultivation of Azadirachta indica and Moringa oleifera in valley areas of Honghe River,Yunnan Province,which have been introduced to the areas for a decade as multipurpose trees.But the flowering period of A.indica and M.oleifera is overlapping with some local plants,which are,Litchi chinensis,Mangifera indica,Capparis wui,Capparis chingiana,and Phyllanthus emblica.Moreover,all of these domesticated and protogenesis plants rely on generalized pollinators.Thus,pollination interference between introduced plant and local protogenesis plant need to be confirmed.Based on research work of pollinating and breeding systems,the extent of local generalized pollinators supporting on introduced plants and the influence on pollination of protogenesis plants could be showed,which is concerned with environmental protection.It could also provide the basic information of formation and maintenance of pollination network for further setting of plant community,improving output of agroforestry system,and benefitting the understanding of plant-pollinator interaction in terrestrial ecosystem,and giving advice to conservation of pollination insects,and also to the strategy and management of domesticated plants blending in local pollination network.The results are as follows:1 Azadirachta indica and.Moringa oleifera were merging into local pollination network,and already set up connections to local pollinators in three aspects:(1)Within the network of 7 plant species and 31 insects,61 connections were observed.In which 20 connections(32.7%)were between domesticated trees and pollinators.(2)The highest number of connections was 13,between A.indica and insects.And the number of connections between M.oleifera and insects was 7,which was more than C.wui and P.emblica.(3)Compared with decade-ago,pollinator species of M.oleifera and A.indica increased 2 and 4 respectively,and frequency increased by 5.4 and 1.7 times respectively.These three aspects showed the evidence of merging into local network.Nested structure of the pollination network showed that there was overlap of pollinators among the exotics plant A.indica and M.oleifera,native plants L.chinensis and M.indica,the protophyte plants C.wui,C.chingiana and P.emblica and the pollinators competition was mainly between exotic plants and native plants.2.According to comparing species and visiting frequency of insects among the 7 plants,the major pollinators of A.indica,M.oleifera,L.chinensis and M.indica were bees.And the major pollinators of C.wui,C.chingiana and P.emblica were butterflies and moths.Thus,pollen interference was mainly occurred between the former 4 tree species.Compared with data of visiting frequency decade-ago,the results showed that:(1)mixed stands could increase visiting frequency of A.indica;(2)mixed stands could decrease visiting frequency of M.oleifera;(3)mixed stands could also decrease visiting frequency of M.oleifera and L.chinensis dramatically.The visiting frequency per day in mixed stands of M.oleifera and L.chinensis was only 19.5% and 39.7% respectively to pure stands,exhibiting pollinators competition.3.Analysis of chemical ecological function of floral scent indicated that bees were the main pollinators among the four plants,which were consistent with the field observations.In the M.indica and L.chinensis mixed stands,the floral scent including 1,8-sineole,acetonitrile,camphor andterpinen-4-ol of M.oleifera and A.indica presented a repelling action against the pollinating insects,which could significantly decrease the visiting frequency of M.oleifera and L.chinensis,resulting a pollinating competition.Moreover,the content of β-Ocimene and Linalool was more than 40.65% in the floral scent of A.indica,showing a strong attraction to bees.And M.oleifera single flowers could produce rich nectar,with 60% Brix and volume of 5-30 μL.Those shows that A.indica and M.oleifera have the ability to merge into the local pollination network.4.The main pollinators of pure M.indica stands,mixed M.indica stands and L.chinensis pure and mixed stands brought the pollen from native plants M.indica and L.chinensis was as high as 72.21-81.45% and 64.13-75.63%,respectively,while the proportion of M.oleifera and A.indica was only 1.13-3.65% and 2.91-6.03%,respectively.Which reveal that the pollinators preferred to visit native plants M.indica and L.chinensis.The visitation rate of M.indica and L.chinensis decreased significantly when they mixed with A.indica or M.oleifera,but there was no significant difference in fruit setting of the 4 main stands.The pollination competition among M.indica,L.chinensis and native plants was only the visiting flower competition,and the pollination efficiency could simultaneously achieve the fruit-set of domesticated and protogenesis plants.The pollination network of A.indica and M.oleifera in the dry-hot valley of Honghe river will not affect the reproduction of native and original plant at the same flowering stage.