Physiological And Ecological Mechanisms Of The Special Natural Enemy Procecidochares Utilis Adaptive To The Invasive Plant Ageratina Adenophora

Ageratina adenophora Sprengel,a notorious weed native to Mexico,is one of the most destructive exotic weeds.In the 1940s,A.adenophora was spread in Myanmar to the south of Lincang City,Yunnan Province,China.Now it has been found in China six southwestern provinces,including Yunnan,Guizhou,Sichuan,Guangxi,Tibet and Chongqing,and it has spread to the north and east of China.Procecidochares utilis Stone,a specialist natural enemy,has been introduced to control the invasive A.adenophora in our country since 1980's,and established normal natural population in some regions,but shows relative poor effect to this weed.Some researches have indicated that the energy of growth and anti-herbivore defences in some invasive plants could reallocate,which was arised from the stress of biotic or abiotic factors.Studies have confirmed that A.adenophora has an adaptive change in herbivore resistance,such as the nitrogen distribution hypothesis,but verification from direct treatments of plant natural enemies and population levels remains unknown.In addition,changes in nutrient content of exotic plant species relative to plant natural enemies are rarely reported,which is necessary to reveal the inner mechanism of "avoiding harm" in the adaptation process of natural enemies to invasive plants.Therefore,with the native and invasive populations of A.adenophora as materials,we compared the plant nutrient contents of the parasitic parts of.utilis before and after the invasion of A,adenophora,and life parameters of the populations,activities of detoxification enzymes,contents of ovarian protein,and its selectivity to the host of P.utilis,in order to reveal the adaptive mechanism of the natural enemies on the invasion plant of A adenophora.The main results are as follows;1.The native(Mexico:Ml,M2 and M3)and invasive(China:C1,C2 and C3)populations of A.adenophora were used as materials to measure the soluble sugar,plant tissue protein and free amino acid content in the tip of the stem(to the prefer parasitic parts of.utilis).The results showed that the soluble sugar content of the native population of A.adenophora was slightly higher than that of the invasive population,but there was no significant difference in the protein content of shoot tip tissue.Among the 17 free amino acids,the urea content was the highest There are seven free amino acids in the invasive population of A.adenophora,which are higher than the in native population,namely glycine,proline,y-aminobutyric acid,valine,serine,alanine and arginine.Among the proline content comparisons,the C2 population was 149.9%,185.5%,and 154.3%higher than that in the native populations M1,M2 and M3,respectively;the C3 population was 186.7%,228.4%and 192.6%higher than that in the M1 and M2 populations,respectively.As to glycine,the C1 population was 72.3%,97.0%,and 73.2%higher than that in the M1,M2,and M3 populations,respectively;the C2 population was 63.3%,87.0%,and 64.4%higher than that in the M1,M2,and M3 populations,respectively.The C3 population was 36.8%,56.4%,and 37.5%higher than that in the M1,M2,and M3 populations,respectively.These results showed that the increased free amino acid content of invasive plant of A.adenophora may be beneficial to the growth and development of P.utilis,meaning more beneficial to herbivorous natural enemies.2.With the method of single-plant treated with the paired insects,the population life parameters,the activities of the acetylcholinesterases,glutathione S-transferases and carboxylesterases and the ovarian protein content of P.utilis reared on native and invasive populations of A.adenophora were also measured and compared;in addition,the host selectivity of.utilis to different populations of A.adenophora was also carried out.Our results showed that the developmental duration of P.utilis reared on the invasive populations of A.adenophora was shorter than natives.The effective egg production and the ovarian protein content of P.utilis reared on the invasive A.adenophora were higher than natives.The acetylcholinesterase activity of P.utilis reared on native populations were generally lower than that of invasives,and the glutathione S-transferase activity was also the same,but the carboxylesterase activity comparison results were reversed.The selective investigation results showed that there was no significant difference for the selection between the native and invasive A.adenophora,but the number of adults per gall was lower than that on the invasives.These results indicated that the invasive A.adenophora was more favorable to the growth of P.utilis,which confirmed the comparison of nutrient content after the invasion of A.adenophora.