Diversity And Dynamic Distributions Of Hymenoptera Communities In Yeyahu Lake Wetland Nature Reserve, Beijing

During the period of April to October 2006,the community diversity and ecological adaptation of Hymenoptera in Yeyahu Lake Wetland Nature Reserve of Beijing was studied by sweep-net sampling.The community composition,diversity,seasonal and spatial dynamics, similarity of Hymenoptera community in different habitats and the characteristic of habitat were analyzed.The results are as follows:1.A total of 60331 Hymenoptera specimens belonging to 30 families were collected, including 4 dominant or sub-dominant Hymenoptera,i.e.Encyrtidae,Eulophidae,Scelionidae and Eupelmidae.A total of 29942 Encyrtidae specimens were belonging to 13 genera.Rhopus,Anagyru, Metaphycus,Mayridia and Cerchysius were the dominant genera.2.The study of spatial dynamics of Hymenoptera showed that the number of Hymenoptera taxa is nearly the same.Set 8 sites in Yeyahu Lake Wetland Nature Reserve.The herb hygrophyte site B and C possessed 30 Hymenoptera taxa which was the most.The number of Hymenoptera taxa in Phragmites australis-Hemathria altissima site E was less.The number in Hemathria altissima site F and Phragmites australi G were the least,and all possessed only 25 Hymenoptera taxa,Phragmites australi site H was more.The individual number of Hymenoptera in site E and F was more,and less in B and C.The individual number Hymenoptera in Site D,G and H were the least.Phragmites australis-Hemathria altissima site E presented obviously different from Hemathria altissima site F,Phragmites australi site G and H3.Season dynamics of Hymenoptera were studied.The number of Hymenoptera individual and taxa in July,August and September were more.The number of Encyrtidae individual and taxa in July and August were the most,and the seasonal preference of 13 Genera were also analyzed.4.Comparative analysis of community composition was conducted by Shannon-Wiener diversity index(H'),Pielou's eveness index(E),Simpson's dominant index(C),Marglef's richness index(D) etc..The results presented that most of diversity indexes in Hemathria altissima site F and Phragmites australis - Hemathria altissima site E were different,which possessed high Simpson's dominant index(C) and low Pielou's eveness index(E). Shannon-Wiener diversity index(H') and Marglef's richness index(D) in site E and F were obviously low.Each Hymenoptera taxa was well-distributed in site B,C,G and H,and these sites all possessed high Pielou's eveness index(E),Shannon-Wiener diversity index(H'),Marglef's richness index(D),low Simpson's dominant index(C).The diversity indexes of Encyrtidae sub-community were smoothly among different sites.The Shannon-Wiener diversity index(H') in site C was the highest,and was the lowest in site E and F.These two sites possessed too many Rhopus,and the Marglef's richness index(D) was low,possessed high Simpson's dominant index(C).Diversity indexes in site G,H were in the middle.Diversity indexes of Hymenoptera communities varied obviously in site E,F in different months,but smoothly in site B,C.Hymenoptera communities in site B,C were complicated and well distributed.The variation of Shannon-Wiener diversity index(H') of Encyrtidae sub-communities in sites were different.Shannon-Wiener diversity index(H') varied obviously in site B,C but smoothly in site E,G and H.Site B and C possessed high Shannon-Wiener diversity index.Shannon-Wiener diversity index in site F was the highest,and possessed the most individual number of Encyrtidae.5.Comparative analysis of community composition was conducted by clustering analysis and principal component analysis(PCA) etc..The results of cluster analysis and principal component analysis presented similar between site G and H in the whole year.Phragmites australis-Hemathria altissima site E was obviously different from Hemathria altissima site F, Phragmites australi site G and H in spring,and more conformable in summer.There presented specialty in site B and C respectively.The composition of Hymenoptera community in site D was particular and separated.Hemathria altissima was distributed more in Hemathria altissima site F,Phragmites australis-Hemathria altissima site E and Phragmites australi site G,H,and the composition of Encyrtidae sub-communities in these sites were similar.5.The results of CCA,basing on individual number of Hymenoptera and environment variables in Aug.,presented community composition was influenced by many environment variables and Margalef richness of plant community,soil water content,total salt content in soil, natrium percentage in soil and soil pH were more prominent.Spearman Correlation coefficients presented that total potassium in soil was significantly positively correlated to soil pH,and the two were significantly negatively correlated to containing soil water content respectively.Total soil total potassium content,diversity of plant community and coverage of plants, mass of defoliation,soil organic matter content,soil total nitrogen content and soil water content were more prominent to the distribution of main Encyrtidae genera.