Species Diversity And Faunal Taxonomic Studies Of Gamasid Mites On Small Mammals In Yunnan (Acari:Mesostigmata:Gamasina)

Gamasid mites,also known as mesostigmatid mites,are a large group of arthropods,including 8280 recorded species over the world and more than 600 species in China.In zootaxonomy,gamasid mites belong to the suborder Mesostigmata(or Gamasida)of the order Parasitiformes in the subclass Acari under the class Arachnida.The living styles and behaviors of gamasid mites are very different from species to species.Some gamasid mites are free living animals while some others are parasites,especially ectoparasites on the body surface of mammals,aves,reptiles,amphibians and even some other arthropods.Rodents and some other small mammals are the most common hosts of ectoparasitic gamasid mites.Of the numerous species of gamasid mites,some ectoparasitic gamasid mites are associated with medicine.Some ectoparasitic gamasid mites can directly lead to dermatitis through their stinging while some others can be the potential transmitting vectors of some zoonoses,such as reckettsial pox and hemorrhagic fever with renal syndrome(HFRS,also called epidemic hemorrhagic fever in China).Yunnan province is located in the southwest of China and it has a vast territory,complex topography and different types of climates with abundant species of plants and animals.Based on accumulated abundant original data and specimens of gamasid mites from the field investigation in Yunnan province between 1990 and 2015,we followed some strategies in the “data mining” and did a further statistical data analysis.The main results are as follows: 1 Species diverisity and faunal distribution of small mammal hostsAll the original data came from the accumulated field investigation in 40 investigation sites of Yunnan province between 1990 and 2015.A total of 17,638 small mammal hosts captured from the 40 investigation sites were identified as 74 species,38 genera and 12 families in seven orders with a high species diversity.Of 17,638 individual hosts,93.094 % of them(16,420/17,638)were rodents(the order Rodentia).Of 74 host species,Rattus tanezumi(or R.flavipectus),Eothenomys miletus,Apodemus chevrieri and R.norvegicus were the dominant host species in the whole province,and their constituent ratios(Cr)were 29.964 %,12.139 %,10.829 %,and 8.210 % respectively.In the five zoologeographical subregions of Yunnan province,the species diversity of small mammal hosts was the highest in the Southern Subregion of Hengduan Moutains(II)with species richness S=57 and Shannon-Wiener's diversity H=2.788 while the species diversity of the hosts was lowest in the Western Plateau Subregion of Yunnan(IV)and the the Southern Mountainous Subregion of Yunnan(V).There were different dominant species of small mammal hosts in different zoogeographical subregions.The hierarchical clustering dendrogram showed that the faunae of small mammal hosts in the subregions IV and V showed a higher value of similarity,and they were clustered as one group in the dendrogram.The faunae of small mammal hosts in the subregions I and II were then clustered as another group.The small mammal hosts in the subregion ?,however,formed an independent group in the dendrogram with the lowest similarity with the above ones.There were 13 species of small mammals widely distributed in all the five subregions and they were epidemic species(wide spread species)of hosts.And 32 hosts species were endemic species,which were only distributed in a certain subregion.2 Species diversity and faunal distribution of gamasid mitesFrom the body surface of 17,638 small mammal hosts,a total of 139,111 individuals of gamasid mites were collected,and they were identified as comprising 39 genera and 156 species in 13 families with a high species diversity.Of 13 families,the family Laelapidae had the most abundant species(104 species)and individuals(130950 individuals),which accounts for 95.438% of all the gamasid mites.Of 156 species of identified gamasid mites,there were 16 main mite species and their total constituent ratio reached 92.97% of all the mites.The most dominant species of gamasid mites in the whole province were Laelaps nuttali,L.echidninus,Dipolaelaps anourosorecis,L.guizhouensis and L.turkestanicus.The individual numbers and species diversity of gamasid mites were positively correlated with those of small mammal hosts(individual numbers: r=0.94,P=0.02;species diversity: r = 0.87,P=0.05)and this suggested that the species diversity of gamasid mites was mainly influenced by the hosts.The faunal similarity and classification of gamasid mites among different zoogeographical subregions were made through the hierarchical clustering analysis,polar ordination and principal component analysis.The faunae of gamasid mites in the subregions I and II were merged into one group and those in the subregions III and V were clustered into another group.The fauna of gamasid mite in the subregion IV,however,formed an independent group.The dominant species of gamasid mites were different in different zoogeographical subregions.Both the oriental and palearctic species of gamasid mites co-existed in Yunnan province with 48.08 % of pure oriental components,35.90 % of pure palearctic components and 16.03% of cross-components appeared in both the oriental and palearctic realms,and this might be associated with the complex topography and obvious elevation differences in Yunnan province.The results of niche breadths showed that there were 27 geographically epidemic(wide spread)species of gamasid mites with a wide scope of geographical distribution.Five species of gamasid mites were “multitude hosts” species and they widely parasitized many species of hosts.These “multitude hosts” species are L.turkestanicus,L.nuttali,H.sunci,D.anourosorecis and L.chini.The results showed that the species diversity of gamasid mites in Yunnan province was much higher than that in some other provinces of China and some other countries.Small mammal hosts were believed to be the most important factor that influence the species diversity and faunal distribution of gamasid mites.Besides the complex topography,multiple landscapes and habitats with different types of climates in Yunnan could also directly or indirectly influence the species diversity and faunal distribution of gamasid mites.Through the indirect influence these factors could make an impact on gamasid mites through influencing the hosts.3 Fluctuations of species diversity and fauna of gamasid mites along different environmental gradientsThe results of this study showed some fluctuations of species diversity and faunae of gamasid mites along different environmental gradients such as different latitudes and altitudes(elevations).The diversities of gamasid mites,including the richnesses and diveristies of species,genera,families,endemic species,oriental components and palearctic components,showed a fluctuation along different latitudes(horizontal gradients).The richnesses and diveristies gradually increased and then decreased with the increase of latitudes.This horizontal fluctuation showed a pattern of single-peak curve with the peak at 25° ~ 27°N of latitudes.The ? diversities of gamasid mites at species and genus levels also showed a horizontal fluctuation along different latitudes.The horizontal fluctuation patterns of species diversity and faunal distribution of gamasid mites were believed to be associated with the fauna transition,fauna heterogeneity and “edge effect” of oriental components and palearctic components at 25° ~ 27°N of latitudes.There were a sries of overlapped species of oriental components and palearctic components in the fauna transitional zones at 25° ~ 27°N of latitudes and this obviously increased the richness and diversity of gamasid mites in the regions.The richnesses and diversities(including ? diversity)of gamasid mites,which covered species,genera,families,endemic species,oriental components and palearctic components,also showed a single-peak curve fluctuation along different altitudes(vertical gradients).The richnesses and diveristies gradually increased and then decreased with the increase of altitudes(elevations).This vertical fluctuation showed a peak at about 2000-3000 m and this fluctuation pattern was also believed to be associated with the fauna transition,fauna heterogeneity and “edge effect” of oriental components and palearctic components at 2000-3000 m of altitudes.4 Species abundance distribution and species-plot relation of gamasid mitesThe species abundance distribution of gamasid mites in the whole Yunnan province conformed to the semilogarithmic distribution pattern and its theoretical curve was successfully fitted with Preston's semilogarithmic model with ?=0.30 and R2=0.9057.Most species(30 species)of gamasid mites in the fauna were those species with two to four individuals while few species were the dominant species with abundant individuals.Baesd on the fitting of theoretical curve of the species abundance distribution,the total expected species of gamasid mites in the whole province were estimated as 177 species and about 21 species were missed out in the field investigation.The species missing was believed to be unavoidable because some species are too rare to be found in the actual investigations.The study on the species-plot relation of gamasid mites revealed that the number of gamasid mite species in the fauna gradually increased with the increase of sampled individuals of their hosts.When the sampled small mammal hosts reached at most 17638 individuals,the curve tendency of species-plot relation was still going up,and this was believed to be associated with the composition heterogeneity of gamasid mite species along different environmental gradients,such as different latitudes,altitudes(elevations)and even different species of hosts.The species composition of gamasid mites might be very different under different environmental conditions.Besides the above results,a new species of gamasid mite,Laelaps jinghaensis sp.nov.,was named and described.All the names identified of gamasid mites,together with their hosts,were listed out in the results.5 Landscapes with different biodiversity and vector gamasid mitesSmall mammal host species(3323 individuals and 55 species)and gamasid mite species(23095 individuals and 88 species)were rich and the constituent ratios of reservoir hosts(E.miletus,15.92%;A.chevrieri,14.17%)and vector gamasid mite(L.echidninus,12.22%)were low in ML.Small mammal host species(18 species)and gamasid mite species(54 species)were rare and the constituent ratios of reservoir hosts(R.tanezumi,88.04%)and vector gamasid mite(L.echidninus,23.77%)were very high in FL.Prevalence(0,0.38%,1.49%)and mean abundance(0,0.02,0.09)of dominant hosts(A.draco,E.miletus,A.chevrieri)infected by L.echidninus in ML were largely lower than prevalence(38.87%)and mean abundance(2.21)of R.tanezumi infected by L.echidninus in FL.