北方草地牛粪中金龟子的多样性

Abstract

Scarab beetles in grassland cattle dung were collected through pitfall traps and dissecting cattle dung in Ewenke Autonomous County(typical steppe),Horqin Left Back Banner(sand steppe) in Inner Mongolia,and Changling County(meadow steppe) in Jilin Province in May-September 2006.Species composition,diversity,and similarity of the scarab communities were analyzed.The pitfall trap method was as follows: A plastic bucket was buried in the experimental plot with the top of the bucket at ground level.The bucket contained a solution of 70% alcohol,and there was an iron wire frame covered with mesh.A nylon bag with 1kg of fresh cattle dung was placed on the iron wire frame.After 3 days,the scarab beetles in the bucket were collected.This procedure was conducted monthly,for 3 successive days,and there were six repetitions in each experimental region.The method for dissecting cattle dung was as follows: select cattle dungs and collect the scarabs in the dung and a 10cm layer of soil under the dung.At least 200 cattle dungs were dissected every month in each experimental region.A total of 75 981 scarabs were captured,belonging to 43 species and 9 families,in which there were 19 species of the family Aphodiidae,9 species of the family Scarabaeidae,6 species of the family Melolonthidae,2 species of the family Trogidae,2 species of the family Geotrupidae,2 species of the family Rutelidae,and each of the families Ochodaeidae,Cetoniidae and Dynastidae had 1 species.There were 10 mutual species among the three experimental regions: Onthophagus bivertex Heyden,O.gibbulus(Pallas),Aphodius breviusculus(Motschulsky),A.haemorrhoidalis(Linnaeus),A.impunctatus Waterhouse,A.naraensis Nakane,A.pusillus(Herbst),A.rectus Motschulsky,A.sublimbatus(Motschulsky),and Proagopertha lucidula Faldermann.In Changling and Ewenke Autonomous County,the dominant species was Aphodius sublimbatus(Motschulsky)(88.188% and 93.547% respectively).In Horqin Left Back Banner,the dominant species were Onthophagus bivertex Heyden(67.067%),Aphodius pusillus(Herbst)(14.524%) and Caccobius unicornis(Fabricius)(10.264%).The diversity analysis demonstrated that the Simpson Index,Shannon-Wiener Index and Pielou Index of the scarab community were highest in Horqin Left Back Banner and lowest in Ewenke Autonomous County.Species numbers of scarabs were in accordance with its richness in cattle dung in different regions.Changling County had the highest richness index,followed by Horqin Left Back Banner and Ewenke Autonomous County.The similarity index of scarab communities between Ewenke Autonomous County and Horqin Left Back Banner was moderately similar at 0.578.The similarity index of scarab communities between Ewenke Autonomous County and Changling County was moderately similar at 0.553.The similarity index of scarab communities between Changling County and Horqin Left Back Banner was moderately dissimilar at 0.458.There were significant differences in the number of scarabs in different regions.Our analysis suggests that four factors result in the differences in diversity of scarab communities in the three experimental regions:(1) Large-scale climatic factors dominate the primary composition of scarab communities;(2) The altitude and latitude of the experimental regions impact the number of families and species of scarabs;(3) Vegetation types impact the diversity and evenness of scarab communities;(4) Grazing pressures impact individual numbers of scarab communities.