Abstract: The aim was to study the species diversity, community structure, similarity, distribution and niche of gamasid mites on the body surface of 3 303 small mammals in the surrounding areas of Erhai Lake in Dali, Yunnan by using Shannon-Wiener, hierarchical cluster analysis (SPSS 13.0) and Levins'niche. The investigated site was an important focus of epidemic hemorrhagic fever, where stands alongside three cordilleras surrounding Erhai Lake, namely Eastern Wuliang Mountain, Southern Ailao Mountain and Western Cangshan Mountain. The three confined oriented areas formed different landscapes within the same zone for inartificial barrier's isolation of Erhai Lake. The small mammal hosts were captured from three differently oriented areas belong to 7 families, 15 genera and 21 species in 4 orders (Rodentia, Insectivora, Scandentia and Carnivora), while 23 196 individuals of gamasid mites collected from the body surface of the small mammal hosts are identified into 6 families, 16 genera and 43 species. The results reveal that the community structure of gamasid mites is complex with high species diversity. The distribution of gamasid mites and their corresponding hosts are quite uneven in differently orientations, but dominant species beside gamasid mites on the same dominant small mammal host in differently oriented areas beside Erhai Lake are homologous. The results indicate that habitat influences the species composition and distribution of gamasid mites and their corresponding hosts. Gamasid mite communities on their corresponding hosts are similar if the taxonomic position and habitats of the hosts (small mammals) are similar. The abundance and diversity of gamasid mites on small mammals across different sites are determined mainly by host identity and by the habitats where the hosts live. This might be an ecological evidence of co-evolution between small mammals and gamasid mites. But by using the niche breadth of gamasid mites, host-specificity of gamasid mites are low, this may imply that the co-evolution between small mammals and gamasid mites exist, but the degree is not high.

Key words: Acari, chigger mite, small mammal, different landscapes within the same zone, community ecology, co-evolution, Yunnan