| First part of this paper is the taxonomic and biogeography study of Euholognatha from China.Euholognatha(Plecoptera:Arctoperlaria)includes about 1600 species representing 90 genera in six families.This study identified and summarized the specimens of Euholognatha collected from China.A total of 4 families,18 genera and 267 species were recorded,including two new genus records,11 new species and three new species records.Meanwhile,the familial and generic key were presented;all new species were illustrated.This study also summarized the detailed distribution of the four euholognathan families in China,and analyzed each family's geographic characters.This part recorded the stonefly fossils of each family,and conducted a brief analysis of the origin and evolution of Euholognatha.The results showed that:1.New genus record:(1)Isocapnia Banks,1938(2)Mesocapnia Rauser,19682.New species:(1)Capnia oblata Chen&Du,2017(2)Capnia trispinosa Chen&Du,2017(3)Capnia xiei Chen&Du,2017(4)Capnia zijinshana Du&Chen,2016(5)Isocapnia anguis Chen&Du,2017(6)Isocapnia apicispina Chen&Du,2017(7)Mesocapnia daxingana Chen&Du,2016(8)Rhopalopsole vespertilio Chen&Du,2017(9)Nemoura fusiformis Chen&Du,2017(10)Kyphopteryx coniformis Chen&Du,sp.nov.(11)Kyphopteryx yangi Du&Chen,sp.nov.3.New species record:(1)Capnia nigra(Pictet,1833)(2)Mesocapnia variabilis(Klapalek,1920)(3)Mesocapnia gorodkovi Zhiltzova&Baumann,19864.Biogeography:(1)Most groups of Euholognatha have a holarctic distribution.Leuctridae and Nemouridae are widely distributed in China,showing specific variations and regional distributions.Capniidae and Taeniopterygidae are typical holarctic groups,having very few records in China and are mainly distributed in western and northern areas,but with an exception in Nanjing,Jiangsu.(2)According to the fossil records and the distribution of extant species,the four euholognathan families all originated from the Pangea Eurasia,and their latest origin should be Jurassic to Cretaceous.Afterwards,most groups dispersed and evolved along with the split of Laurasia.The second part of this paper is the molecular phylogenetic study of Plecoptera from China.Plecoptera belongs to Insecta,Hexapoda,and Arthropoda.Phylogenetic position and inner relationships of Plecoptera are still debatable.This study sequenced and analyzed 10 mitochondrial genomes from eight families of Plecoptera and rebuilt the phylogeny of Plecoptera based on all available mitochondrial genomes.Different analysis methods and datasets were used to investigate their influences on topology of the phylogenetic trees.This study provided basic data and methods for the molecular phylogenetic studies of Plecoptera in future.The main results of this part are as follows:(1)Structure and base composition of the 10 mitochondrial genomes are highly conserved.The average length is 1.6 kb,the average A+T content is 70%.All mitochondrial genomes of Plecoptera contains 37 genes,including 13 PCGs,22 tRNA genes,2 rRNA genes and a non-coding control region.Position and orientation of these genes are consistent with the model insect,Drosophila yakuba.For each gene,the length and base composition are also highly conserved among different mitochondrial genomes.Most PCGs start with the standard ATN and end with TAN,but some PCGs also have special start codons GTG and TTG and the incomplete stop codon T.Most tRNA genes have a typical cloverleaf secondary structure,but the DHU arm of trnSerl(AGN)is reduced or lost.The anticodon is consistent in the same tRNA gene of all plecopteran mitochondrial genomes.There're some mismatched base pairs in the tRNA genes,and most of them are G-U pairs.The two rRNA genes are very conserved in position,length and base composition.(2)In all available plecopteran mitochondrial genomes,the control region is conserved in its location,but is highly variable in its length,base composition and structure.There're usually some special structural elements,such as stem-loop structures,tandem repeats and conserved sequence blocks in the control region.(3)The higher-level phylogeny of Plecoptera is analyzed based on mitochondrial data from 22 species of 11 families using two methods and five datasets.The results indicate that the mitochondrial data can separate the two suborders Arctoperlaria and Antarctoperlaria and can separate the two infraorders Euholognatha and Systellognatha.In the family level,Leuctridae might be the basal group of Euholognatha;Capniidae might be the sister group of Taeniopterygidae or Nemouridae,However,in Systellognatha,the monophyly of Perloidea and Pteronarcyoidea is not supported,but Pteronarcyidae,Perlodidae and Chloroperlidae are usually grouped together.In addition,the partition of different gene types,the combination of PCG and rRNA,and the usage of BI method can improve the support and reliability of the phylogenetic tree.Due to the incomplete sequencing of all families in Plecoptera,the complete topology of Plecoptera is still unavailable. |
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