Researches On Parasitical Condition Of Chigger Mites On Small Mammals (Non-muridae) In Yunnan Province, China

Objectives:(1) To research the species composition, species diversity, community structure and species abundance of chigger mites on their Non-Muridae small mammal hosts.(2) To study the spatial distribution pattern of dominant chigger mites from every Non-Muridae small mammals respectively.(3) To discuss the changes and variation trends of chigger mites on their Non-Muridae small mammal hosts when localities and altitude change.Methods:(1) The original data came from the field sample investigation in20locations of Yunnan Province from2001to2010;(2) the structure of community and diversity of species were analysed with the constituent ratio (Dr), chigger mite infected rate (Rm), chigger mite index (IM), species richness (S), Shannon-Wiener diversity index (H’), evenness (J) and dominance index (C’);(3) The coefficient (C), cassie index(CA) and patch index(m*/m) were applied to measure the spatial distribution pattern;(4) Niche breadth method (Shannon-Wiener index and Simpson index) and Pianka’s niche ovelap index were used to discribe the niche of the dominant species of chigger mites. Based on Pianka’s niche overlap index of the dominant species, hierarchical cluster analysis (SPSS16.0) was used to classify the niche overlapping groups;(5) The model of Preston’s logarithmic normal distribution was used to fit the theoretical distribution curve of species-abundance of chigger mites, and the total species number of chigger mites was estimated based on the theoretical distribution curve.Results:(1) During2001to2010, a total of3470individuals of Non-Muridae small mammals were capured and identified as five orders (Rodentia, Insectivora, Scandentia, Lagomorpha and Carnivora),11families,25genera and46species (contain2undetermined species). And68577individuals of chigger mites were collected from their Non-Muridae small mammal hosts and identified as3subfamilies,22genera and180 species (contain13undetermined species). Eothenomys miletus and Nowrosorex Squamipesi were the dominant Non-Muridae small mammal hosts, and the Dr were54.81%and10.37%respectively.(2) The species composition of chigger mites and their Non-Muridae hosts changed in different localities and altitude interval. Below1500m height areas, the main Non-Muridae hosts were Suncus murinus and Nowrosorex squamipesi, and the dominant chigger mite was Leptotrombidium deliense. But above1500m altitude, the main Non-Muridae hosts and dominant chigger mite were E. miletus and L. scutellare separately.(3) The chigger mites from Non-Muridae hosts with high species diversity and low host specificity.(4) The taxonomic relationship and related level of Non-Muridae small mammal hosts, localities,habitats and altitude are not have a good correspondence to the similarity of chigger mites, there may have other complicated factors to impact the similarity of chigger mite community on their Non-Muridae hosts.(5) Most chigger mites from Non-Muridae hosts have a wide host range (3-16species), but relatively low niche breadths, because lots of them mainly parasitize one or few species of Non-Muridae hosts’body surface. Most chigger mites can disproportionately overlap each other, and54.74%overlaped indices above0.5. Based on the hierarchical clustering analysis,20species of dominant chigger mites were classified into4niche overlapping groups when X=10in the clustering dendrogram.(6) After large numbers of model simulating, the species-abundance of chigger mites from tree shrews get some good result when a=0.226(R2=0.7216), and the theoretical distribution curve presents approximate logarithmic normal distribution. The individuals of most chigger mites are range from14to121. The total species number of chigger mites was estimated as110species based on the theoretical distribution curve.Conclusions:(1) The species of Non-Muridae small mammals and their ectoparasite chigger mites are extremely abundant in Yunnan Province with high biodiversity. The discretion of Non-Muridae small mammals’biodiversity affect the species diversity of chigger mites directly. The unique topography and climate features of Yunnan Province also can influence the rich biodiversity of chigger mites primely.(2) The species constitute of Non-Muridae small mammals and their ectoparasitic chigger mites changed in different localities,altitude or habitats. Below1500m height areas, the main Non-Muridae hosts were Suncus murinus and Nowrosorex squamipesi, and the dominant chigger mite was Leptotrombidium deliense. But above1500m altitude, the main Non-Muridae hosts and dominant chigger mite were E. miletus and L. scutellare separately. The vector chigger mites in Yunnan Province are different from other areas in south of Yangtze River.There may coexist various species of vectors to transmitting scrub typhus,such as L.deliense,L. scutellare and so on.(3) Each dominant chigger mite on their Non-Muridae small mammal hosts presents social parasitism. The taxonomic relationship and related level of Non-Muridae small mammal hosts, localities,habitats and altitude are not have a good correspondence to the similarity of chigger mites, there may have other complicated factors to impact the similarity of chigger mite community on their Non-Muridae hosts.(5) Most chigger mites from Non-Muridae small mammal hosts have a relatively narrow niche breadth but wide host range, high niche overlap and low host specificity because of the uneven distribution on different Non-Muridae small mammal hosts. This means some co-evolutionary relationship exists between chigger mites and their hosts, and the host choice of chigger mites is extremely less rigorous because they have widespread cross parasitic each other.(6) The species-abundance theoretical distribution curve of chigger mites from tree shrews presents approximate logarithmic normal distribution, and the total species number of chigger mites was estimated as110species based on the theoretical distribution curve.