| Objectives:The present study is to analyze the species distribution patterns and related ecological aspects of three species of chigger mites,Leptotrombidium imphalum,L.rubellum and Walchia micropelta,in Yunnan province of southwest China.The analyses covered the horizontal distribution patterns in different zoogeographical regions,the habitat selection and host selection of the three mite species,together with their spatial distribution patterns on their main hosts,their interspecific relationship and seasonal fluctuation.Methods:The original data came from the accumulated field investigations in 34 sites of Yunnan province,southwest China from 2001 to 2017.The study contains two parts,one from 34 sites of Yunnan province from 2001 to 2015,the other from the monthly investigation at Jingha site between April 2016 and March 2017.Every specimen of the chigger mites on the glass slides was finally identified into species under a microscope.The constituent ratio(Cr)was used to compare the distribution of the mites in different investigation sites,landscapes and on different hosts.The infestation prevalence(P_M),mean abundance(MA)and mean intensity(MI)were used to analyze the infestation of every chigger species on their hosts and the tendency of their host selection.The arithmetic mean(m),variance(?~2)and K value from the negative binomial distribution were used to determine the spatial distribution patterns of the chiggers on their hosts.Non-parametric Mann-Whitney U-test was adopted to test the differences of the chigger abundance and richness in female and male hosts.The association coefficient(V)was used to measure the interspecific relationship between two species of the chigger mites.The seasonal fluctuation was expressed by conventional seasonal fluctuation curve.Results:Of 129,024 collected mites,127,460 individuals of them were identified into 277 species and the rest 1564 mites remained unidentified because of the blur structure or body damage in some specimens and some suspected new species.All the collected chigger mites were identified as 3 subfamilies,26 genera and 277 species.A total of 129,024 individuals of chigger mites were collected from the body surface of all the captured small mammal hosts.Among the 127,460 chigger mites identified,the constituent ratios(Cr)of L.imphalum,L.rubellum and W.micropelta were 0.92%%,0.55%and 3.15%,respectively.The three species of chigger mites are mainly collected from Xishuangbanna area in southern Yunnan.Leptotrombidium imphalum and L.rubellum were mainly distributed in the flatland landscape,while Walchia micropelta was mainly distributed in the mountainous landscape(P<0.01).All the species of chigger mites can be parasitic on the body surface of various small animals with low host specificity and their main hosts and infestations are significantly different(P<0.05).The dominant hosts of L.imphalum was Rattus tanezumi(Cr=59.90%).However,the infestation parameters of L.imphalum on the body surface of Niviventer sinensis was the highest(P_M=27.66%,MA=6.00,MI=21.69,P<0.05).Rattus tanezumi(in Order Rodentia)harbored 94.04%of the total collected individuals of L.rubellum with relatively high mean intensity(MA=0.24,MI=8.84mites/per host)(P<0.05).The dominant hosts of W.micropelta were R.brunneusculus and R.tanezumi with 28.90%and 25.46%of the mites collected from these two rat species.The prevalence(infestation rate)and mean abundance(average abundance)of the chigger mites on the body surface of Leopoldamys edwardsi(P_M=25.00%,MA=4.75)were higher than those of most other hosts(P<0.05).The patchiness index(m*/m>1)and the K value of negative binomial distribution(K>0)showed that the three species of chigger mites had an aggregated distribution pattern among different individual of their hosts.An obvious positive association existed between every two species of the chigger mites according to the coefficient of association(V>0,P<0.01).Based on the field investigation at Jingha of Yunnan province,southwest China between April 2016 and March 2017,a total of 2434 small mammal hosts were identified as 15 species,10 genera and 5 families in four orders.Of the identified 109,199 individuals,the individuals of L.imphalum,L.rubellum and W.micropelta were 99,659 and 34922,and their constituent ratios(Cr)were 0.09%,0.60%and 31.98%respectively.It showed that L.rubellum and L.imphalum had a seasonal fluctuation with a single peak in October and November.The monthly variation of W.micropelta was not obvious,and the number in May was slightly higher than that in other months.Conclusions:The three species of chigger mites are mainly distributed in southern area of Yunnan province with lower latitude and altitude.Leptotrombidium imphalum and L.rubellum are mainly distributed in the flatland landscape,and W.micropelta mainly in the mountainous landscape.All the three species of chigger mites can live on many hosts with low host specificity.The dominant hosts of L.imphalum and L.rubellum are R.tanezumi,and the dominant hosts of W.micropelta are R.brunneusculus and R.tanezumi.The three species of chigger mites are of aggregated distribution among different individuals of the corresponding main hosts,and they tend to select the same hosts simultaneously.The seasonal fluctuation of L.rubellum and L.imphalum are obvious with the peaks in October and November.There is no obvious seasonal fluctuation of W.micropelta. |
PDF Full Text Request