Spatial Distribution Pattern Of Two Natural Enemies Of Citrus Pests At Different Scales

In this paper,dragonflies and ladybugs were taken as the examples to explore the distribution pattern of the natural enemies of citrus pests using cluster analyses and diversity indices.Main results were as follows:(1)At the regional scale,there were 151 genera of dragonflies in China,which were suitable to be divided into 3-7 groups;while 89 genera of Chinese ladybugs were suitable for 2-4 groups.There were obvious common points within the insect sub-regions,and the new clusters often referred to the special geographical areas such as Qiangtang area,Ganzi+Medog area,and southern Xinjiang area.The distribution pattern of natural enemies of citrus pests at the regional scale were closely related to China's “three-step staircase” and “three vegetation belts”,and each small unique area would gradually separate as one single cluster with the increasing of group number.(2)At the local scale,a total of 983 dragonflies belonging to 48 species,31 genera and 8 families were collected,including 610 individuals of 42 species in Wuzhifeng(WZF)of Shangyou County,261 individuals of 23 species in Shangzhai(SZ)of Shangyou County and 112 individuals of 13 species at Gannan Normal University(GNNU).For ladybugs,434 individuals were collected from 11 genera,14 species,3 subfamilies,including 188 individuals of 12 species at WZF,178 individuals of 11 species at SZ and 68 individuals of 7 species at GNNU.In general,the distribution pattern of the species diversity of dragonflies and ladybugs at three habitats were consistent with the environmental stress hypothesis.(3)According to taxonomic diversity indices,dragonflies had highest species number and highest total taxonomic distinctness(S Delta+)at WZF;three indices including taxonomic diversity(Delta),taxonomic distinctness(Delta*)and average taxonomic distinctness(Delta+)showed the trend of SZ > WZF > GNNU;index of variation in taxonomic distinctness(Lambda+)was highest at GNNU,indicating lowest taxonomic evenness of dragonflies at GNNU.For ladybugs,all six taxonomic diversity indices were generally ordered as WZF > SZ > GNNU,that is to say,ladybugs had highest taxonomic diversity and evenness among the three habitats.(4)The total DNA of the citrus pest natural enemies was extracted using the Ezup column animal genomic DNA extraction kit.Sequencing after PCR amplification,sequencing results were used to construct ML tree of dragonflies.Phylogenetic diversity indices at three habitats were calculated based on maximum likelihood(ML)tree of dragonflies.Among the three habitats,dragonflies had closest phylogenetic distance,highest phylogenetic diversity,highest phylogenetic species variability,highest phylogenetic species clustering and highest phylogenetic species richness;all the indices generally decreased with increasing of disturbance level.The MNTD index at the three habitats did not differ much,with a bit higher value at SZ.Phylogenetic species evenness was ordered as SZ > WZF > GNNU.(5)According to functional diversity indices at the three habitats,dragonflies had highest functional richness and lowest functional dispersion at WZF,but highest functional evenness at SZ.Among the functional clustering groups of dragonflies,there were all four groups at WZF and SZ but only two groups at GNNU.In general,functional diversity of dragonflies was ordered as SZ > WZF > GNNU.In a conclusion,the distribution patterns of natural enemies at regional scale were closely related to large-scale biogeographic patterns in China.At local scale,the distribution patterns of species diversity,taxonomic diversity,phylogenetic diversity and functional diversity were not always consistent,but all diversity indices showed a certain law: diversity was always lowest at the most disturbed area,while the responses of different insect groups to low disturbance level or intermediate disturbance level might be different.