The Taxonomics Of Unionicolidae From China With Molecular Phylogenetic Analysis Wthin The Family

Unionicolidae(Arachnida: Trombidiformes: Hygrobatoidea)is one of the groups with higher species diversity in Hydrachnidiae,which is widely distributed in the world.A total of 694 species belonging to 13 genera have been reported worldwide,and of them 46 species and 3 genera have been previously recorded from China.Larval stages of the most members of the family are predators of water invertebrates and their nymphs and adult stages are parasitic or free-living.Whereas some even are parasites of molluscs(Porifera: Spongillidae,Ampullarioidea: Viviparidae,Unionoida:Mutelacea & Unionacea,and so on)from their postlarval to adult stages.At present,taxonomics of Unionicolidae are still in the alpha stage,and there are some key issues,such as difficult to identify closely relative species,unclear about phylogenetic relationship among taxa,need to be solved or propelled.This research was carried out with focus on the above issues and emphasis on taxonomy,morphological and molecular phylogeny.1.Classification with detailed illustration of the taxa new to science and newly recorded from ChinaA total of four genera,19 subgenera and 91 species were identified and described in this dissertation,with a numbers of taxa new to science and China The taxa new to science or new to China are as follows: four new subgenera,Egeoglandula,Vespicola,Micronodicola and Lingshuiatax;one newly recorded genus,Nyangalla Viets,1935,and three newly recorded subgenera,Soarella Koenike,1907,Lemienia Koenike,1910,Armatax Bader,1981;five new combines: Neumania(Lemienia)megaspina Jin 1997(from subgenera Neumania),Neumania(Lemienia)heterotaxis Jin,1997(from subgenera Neumania),Neumania(Egeoglandula)disetus Jin,1997(from subgenera Neumania),Neumania(Egeoglandula)dolichotricha Jin,1997(from subgenera Neumania),Neumania(Egeoglandula)cercalis,Jin 1997(from subgenera Neumania);41 new species and six newly recorded species.2.Phylogenetic analysis based on morphological and biological characteristicsThe phylogenetic analysis of Unionicolidae by using TNT ver.1.1 based on 94 morphological and one biological characteristics.The results of cladistics shown that all five subfamilies of Unionicolidae monophyly,and the phylogenetic relationships are showed as Unionicolinae +(Encentridophorinae +(Omanohydracarinae +(Pionatacinae + Pollicipalpinae)));The taxonomic status of the three new subgenera are supported.Within the subfamily Koenikea and Recifella seem to be the sister group,which supports Cook’s proposition to promote Recifella and Tetraneumania from subgenera to genera,and Vidrine’s suggestion to demote Vietsatax to subgenus.3.Detecting approximate species based on COI sequenceWith DNA barcording based on COI sequences of the three closely related Neumania species,phylogenetic trees were constructed with the maximum-likelihood(ML)and neighbour-joining(NJ)methods by using the MEGA X software.The three similar species,N.tribreviseta,N.paratribreviseta and N.ponsa,were demonstrated as valid species and successfully paired their sexes by genetic distances.4.Phylogenetic relationships based on molecular dataThree molecular markers methods,mitochondrial COI gene,ribosomal 28 s r RNA gene and full mitochondrial genome,were used to construct phylogenetic tree.The mt DNA of five representive species in two subfamilies of Unionicolidae were sequenced and analyzed.It revealed that gene rearrangement presents in mt DNA sequence of Neumania panoplosa.The phylogenetic tree showed that Pionatacinae and Unionicolinae were monophyly;the taxonomic status of Micronodicola and Egeoglandula were approved.The consensus tree constructed by three molecular data well illustrated the sister lineage among genera of Unionicolinae,which was(((Parasitatax+ Wolcottatax)+ Unionicola)+ Unionicolides).5.Biogeographic featuresFollowing World Zoogeographic Division and Zoogeographic Division of China,the faunal feature of Chinese Unionicolidae was analyzed based on species distribution from the field investigation and documentary information.The results revealed that the Unionicolidae fauna of South China,Central China and Northeast China had strong influence on other four regions,and Qinghai-Tibet component was weakly related that of other six regions,At the subgenus level,those of South China and Central China were absolutely dominant.And the Chinese Unionicolidae fauna showed two prominent characteristics,the ancient origination and juvenile speciation at lower taxon level.On the zoogeographic realms of world,Chinese Unionicolidae fauna has the distribution traits of the Palaearctic and Oriental components,and closest linage with the Nearctic,followed by the Ethiopian,and lowest with the Neotropical realm.It is proposed that the Unionicolidae originated form the central and eastern part of Laurasia region in Pangaea,and completed the initial distribution at generic level before the disintegration of the Pangaea.As one of water mite groups with abundant in species,the research on Unionicolidae previously done is relatively lagging behind.By a comparative investigation of Chinese Unionicolidae,the dissertation described the taxa in detail,clarified zoogeographic features,elaborated phylogenetic relationship among higher Unionicolidae taxa based on morphological and molecular.The results laid a foundation for further study of Unionicolidae in China and even worldwide.