Impact Of Nectar Robbing On Female Reproductive Success Of Impatiens Oxyanthera (Balsaminaceae) Under Simulated Climate Warming

Plants and pollinators have different response to climate change,then that leads to the pollination crisis,which has received a lot of attention.Nectar robbing is one of the key biological factors affecting the symbiosis between plants and pollinators.We studied the effect mechanism and ecological consequences of nectar robbing on the interaction between plants and pollinators under simulated climate change.That would reveal the influencing mechanism of climate warming on the reproductive success of plants and the reproductive adaptation strategies of plants,and provide theoretical support for the protecting and reproducing of the specie.We took the Impatiens oxyanthera(Balsaminaceae)as the research object,which grows in Mt.E’mei,Sichuan Province,southwestern China.We set up 12 experimental plots in Mt.E’mei,and cultivated a total of 432 potted plants of I.oxyanthera.We made 6 experimental plots be elevated temperature by the infrared heater,while the rest of 6 experimental plots were labeled as non-warming plots.After the artificial control experiment and the natural observation,we studied the impact of nectar robbing and warming o n female reproductive success of I.oxyanthera and compared the nectar standing crop,individual flower longevity,pollinator behavior and simple fruit seed set.The main results as follows:1.In warming experimental plots,the soil temperature was significantly improved(1.12 + 0.08)℃(t=13.996,P<0.001),and the air temperature was significantly elevated(1.89 + 0.09)℃(t=20.091,P<0.001),while the air humidity was significantly reduced(10.55 + 0.42)%(t=25.111,P<0.001),which means that simulated warming is effective.2.In the experiment of insulating pollinators or nectar robbers by covered corolla or nectar spur with colorful(black,white,green and red)gauze bags,we compared the mean visit frequency and foraging time of visitors for covered flowers,and then we found that the flowers covered by white gauze bags with minimum interference to visitors.3.In the experiment of measuring robbing position,we found nectar robbers mainly robbed the 1/4 to 1/2 of position(to the top of spur)of nectar spur,and we concluded that nectar robbers had no direct damage to the nectary during the nectar robbing because the nectary was located at the top of nectar spur of I.oxyanthera.4.Warming had no significant impact on nectar volume(P>0.05),but nectar robbing made nectar volume change obviously(P<0.05),that is to say,nectar robbing significantly reduced nectar volume by 99.68%(P<0.05)and 98.04%(P<0.05)in the non-warming and warming experimental plots.Besides,warming had no significant impact on nectar sugar concentration.So we concluded that nectar volume and sugar concentration of I.oxyanthera were not sensitive to warming,but nectar robbing had remarkable impact on nectar volume.We did not measure nectar sugar concentration of robbed flowers,because they remained little nectar volume.5.Warming made no significant impact on individual flower longevity,but nectar robbing significantly reduced individual flower longevity by 1.2d(P<0.05)and 1.1d(P<0.05)in the non-warming and warming experimental plots.But the flowers of I.oxyanthera were hermaphroditic.Owing to protandry,nectar robbing significantly reduced the androecium stage by 1d(P<0.05)and 0.8d(P <0.05)in the non-warming and warming experimental plots.However,the gynoecium stage was not affected significantly by nectar robbing(P>0.05).Thus we concluded that nectar robbing made the flowers enter the gynoecium stage earlier than the unrobed flowers,but there was no difference on the gynoecium stage between robbed flowers and unrobed flowers.6.Both warming and nectar robbing had no significant impact on mean visit frequency and foraging time of pollinators(P>0.05),therefore we concluded that pollinator bumblebees were able to control their body temperature to adapt to the warming environment.Although nectar robber reduced nectar volume,pollinator bumblebees would still visit the robbed flowers.7.Although simulated warming changed the temperature and humidity of experimental plots,warming had no remarkable impact on nectar volume,nectar sugar concentration,individual flower longevity and pollinator behavior,however,nectar robbing significantly reduced nectar volume and individual flower longevity.But nectar robbing had no impact on pollinator behavior.At last,both warming and nectar robbing had no significant impact on simple fruit seed set of I.oxyanthera(P>0.05),so we concluded that warming and nectar robbing had neutral effects on simple fruit female reproductive success of I.oxyanthera.