Diversity And Distribution Pattern Of Insect Communities In Salt Marsh Wetland On Yangtze River Estuary

In order to study the diversity and distribution pattern of insect communities in the salt marsh wetland on Yangtze River Estuary, we collected insect by net sweeping, plant reaping and wilt collecting methods at sampling sites which were setted in the Scirpus mariqueter communities, Spartina alterniflora communities, and Phragmites australis communities of Jiuduansha wetland and Dongtan wetland, in four seasons from January to October in 2008. A total of 29242 insects were collected. We compared the composition and diversity indices of insect communities in different elevation, and used principal component analysis to discuss the relationship between insect community and plant factors. The characteristics of diversity and distribution pattern of the insect communities on the tidal creek have been revealed. The main conclusions are as follows:1. The composition of insect community in salt marsh wetland of Yangtze River Estuary is relatively abundant. Up to the present, 12 orders, 60 families, 82 species of insects from Jiuduansha wetland and 13 orders, 52 families, 68 species from Dongtan wetland have been identified.2. The insect species and individuals of various elevations are different. In general, the number of insect species collected by net sweeping methods is enhancing as the increasing elevations. The number of insect species and individuals collected by plant reaping and wilt collecting methods are both enhancing as the increasing elevation.3. The dominant groups and sub-dominant groups of of various elevations are not the same. However, both Diptera and Coleoptera as dominant groups or sub-dominant groups live in every elevation. The proportion of Diptera reduce as the elevation increase. 4. Insect diversity indices show seasonal dynamics. Indices between seasons are significant different. Shannon-Wiener index and Pielou evenness index in summer and autumn are mostly higher than in spring and winter. Simpson dominance index is opposite.5. The distribution of insect communities of various elevations showed a certain pattern. Shannon-Wiener index and Pielou evenness index of insect communities in Spartina alterniflora of Jiuduansha wetland are both enhancing as the increasing elevation, but Simpson dominance index is opposite. However, there is no significant difference between insect communities in Phragmites australis. The trend of insect communities in Dongtan wetland is same as the former.6. The similarity of insect communities of various elevations is different. Cluster analysis indicated that the similarity of insect communities in Spartina alterniflora of medium marsh and high marsh in Jiuduansha wetland is higher than others. And it also indicated that the similarity of insect communities of low marsh and medium marsh in Dongtan wetland is higher than others.7. There is a inter-relationship between insect community and some plant factors. The insect community in Jiuduansha wetland is relevant with plant density. Meanwhile, the insect community in Dongtan wetland is relevant with the combination of the above-ground biomass of plants and marsh conductivity.