Host And Environmental Selection Of Three Species Of Rombiculid Mites Including Leptotrombidium Scutellare In Yunnan Province, China

Objectives: To investigate the geographical distribution, spatial distributionpattern and host selection of Leptotrombidium scutellare, Leptotrombidium yui andHelenicula simena among different small mammal hosts in some areas of Yunnanprovince, China.Methods: A field survey was carried out in23counties of Yunnan provincebetween2001and2011. The small mammal hosts were captured with mouse cagesand traps with baits. The chigger mites on the surface of two auricles were scraped offby a bistoury, and then preserved in70％ethanol．Every specimen of the chigger miteson the slides was finally identified into species under a microscope. Someconventional statistical methods were adopted to calculate all the collected chiggermite species, which include the constituent ratios of chigger mites in different areasand on different hosts, together with its prevalence (P), mean intensity (MI) and meanabundance (MA) on different hosts. The patch index (m~*/m) was used to measure thespatial patterns of chigger mites among the different individuals of its small mammalhosts. Non-parametric Mann-Whitney U-test was adopted to test the differences ofectoparasite abundance and richness in female and male hosts．Spearman correlationanalysis was used to analyze the relationship between ectoparasites and the body parameters of the hosts．Coefficient of association（V）was used to measure theassociation relationship between two species of the chigger mites. Niche breadthmethod (Simpson index) and Pianka’s niche overlap index were used to describe theniche breadth and niche overlaps of the chigger mites.Result： Between2001and2011,11817small animals were captured in23countries of Yunnan. The captured small mammals were identified as five orders（Rodentia, Insectivora, Scandentia, Lagomorpha and Carnivora）,12families,34genera and67species. A total of108480individuals of chigger mites were collectedfrom the body surface of all the captured small mammal hosts. All the collectedchigger mites were identified as3subfamilies,24genera and234species. L.scutellare, L. yui and H. simena were mainly distributed in the middle and highaltitude regions, and their dominant hosts were voles. Of234species of chigger mites,17325individuals of L. scutellare were collected from14counties. The collectedindividuals of L. scutellare accounted for15.97％of the total mites (108480individuals). The dominant hosts of L. scutellare were Eothenomys miletus andApodemus chevrieri. There were1959individuals of L. yui collected from9counties.The collected individuals of L. yui accounted for1.81％of the total mites. Tupaiabelangeri (in Order Scandentia) harbored42.16%of the total collected individuals ofL. yui with relatively high prevalence (P=26.52%) and mean intensity (MI=13.54mites/per host), and other wild-dwelling small mammals came next. There were5501individuals of H. simena collected from7counties. The collected individuals ofH. simena accounted for5.07％of the total mites. The dominant host of H. simenawas Eothenomys miletus. The patch index showed that the three species of chiggermites had an aggregated distribution pattern among different individual of their hosts.There were no obvious correlation between the individual number of chigger mitesparasitized on small mammal hosts and the parameters of their small mammal hosts（male and female, age and body weight）. A slight positive association existedbetween each two species of the chigger mites according to the coefficient ofassociation（V）. The niche breadth of the three chigger species showed the following tendency: L. scutellare> L. yui> H. simena. There was a wide niche overlap betweenany two chigger species.Conclusions:（1） The community structure of chigger mite community iscomplex in Yunnan Province with a very high species diversity. L. scutellare, L. yuiand H. simena were mainly distributed in the middle and high altitude regions.（2）The constituent ratios of L. scutellare was highest, which was considered as thedominant chigger species of Yunnan Province.（3）The preferences of L. scutellare, L.yui and H. simena to their small mammal hosts were not prominent and not strict.They can choose a variety of small mammals as their hosts with very low hostspecificity. The main dominant hosts of the three species of chiggers were wild smallmammals, especially voles.