Studies On The Comparative Mitochondrial Genomics And Phylogeny Of Heteroptera(Insecta:Hemiptera)

With seven infraorders,nearly 80 families and more than 40,000 described species,Heteroptera(Insecta:Hemiptera)are worldwide distributed which include a large number of agricultural pests,animal parasites and natural enemies.Relationships among the infraorders of Heteroptera have still been controversial,especially the relationships between Enicocephalomorpha,Dipsocoromorpha,Gerromorpha,Nepomorpha and Leptopodomorpha.What's more,the monophyly of Cimicomorpha is still in doubt.Insect mitochondrial genome(mt genome)has been widely used in the studies of phylogenetic relationships,population structure and so on.However,there are still many problems in the recent studies of the phylogenetic relationships within Heteroptera based on mt genomes,such as the influence of base composition and evolution rate heterogeneity,model selection and the data lack of some taxa.In this study,to further expand the sampling we determined the mt genomes of 30 insects of 15 families from five Heteropteran infraorders,putting emphasis on Enicocephalomorpha,Leptopodomorpha and so forth.We conducted the comparative analyses of base composition,evolution rate and gene rearrangements of 130 heteropteran mt genomes.The main results are as follows:(1)There was significant heterogeneity between taxa in both the base composition and evolution rate of heteropteran mt genomes:the AT content and evolution rate of mt genomes of Tingidae,Enicocephalomorpha,Dipsocoromorpha and Gerromorpha were higher than others,and those of Reduviidae,Nepomorpha and Leptopodomorpha were relatively lower.(2)We found out seven kinds of gene rearrangements in 19 species belonging to seven families.Thereinto,the same gene shuffling occurred in the mt genomes of five species in Enicocephalomorpha and the mt genomes of Enicocephalomorpha presented a trend of accelerated evolution.The gene rearrangements in Ceratocombidae,Reduviidae,Aradidae and Pyrrhocoroidea only involved RNA genes.Considering these features of Heteropteran mt genomes,we conducted the comparative analysis of phylogenetic relationships under both homogeneous and heterogeneous model using two datasets.We got the results below:(1)Under the homogeneous model,the phylogenetic analysis was affected by the base composition and evolution rate heterogeneity and led to systematic errors:those taxa with high AT content and high evolution rate always formed a clade,such as Tingidae,Enicocephalomorpha,Dipsocoromorpha and Gerromorpha,and those of low AT content and rate clustered together,Reduviidae,Nepomorpha and Leptopodomorpha.(2)By using the heterogeneous model,we eliminated or reduced the systematic error,and the phylogenetic results were:(Enicocephalomorpha,Dipsocoromorpha,Gerromorpha)+(Nepomorpha +(Leptopodomorpha +(Reduviidae +(Cimicomorpha + Pentatomomorpha)))).Our results suggested that the use of mt genomes data for resolving deep phylogenetic relationships required an assessment of the potential impact of compositional and evolutional biases by using site-heterogeneous mixture models.And emphases should be placed on increasing the mt genome data of Enicocephalomorpha,Dipsocoromorpha and Leptopodomorpha to further explore the phylogenetic relationships within Heteroptera.