| Although Hymenoptera is one of the first animals to carry out genome research,most of the main lineages of the genome resources still lack of depth research,and the use of molecular sequences for phylogenetic reconstruction still faces many problems.Gene rearrangement as genome-level characters beyond linear sequences comparison is conservative in most groups which may provide important information for phylogenetic analysis.Further study of mitochondrial genome rearrangements in the basal lineages of Hymenoptera is helpful to support the controversial phylogenetic relationship,which is a great theoretical significance for the study of the early evolutionary history of Hymenoptera.In this study,we selected 332 mitochondrial genomic data from typical groups of 15 families in the basal lineages of Hymenoptera and 51 mitochondrial genomic data from 26 families of 14 superfamilies of Aportia for analysis.The main characteristics are as follow:(1)According to previous studies,some notable rearrangements in Hymenoptera are limited to the isolated groups of Aportia.However,the near-complete genus-level sampling results of this work indicate that the mitochondrial genome of Hymenoptera is a good model for observing gene rearrangements.There is more diversity of gene rearrangements than expected,this makes us cautious about the conclusion that gene rearrangements mainly occur in parasitic groups.(2)Despite the high frequency of gene rearrangements in the basal lineages of Hymenoptera,analysis of gene rearrangements and phylogenetic trees showed that species from the same family or genus have similar gene sequences,and conservative gene blocks(cox1-cox2、cox3-trn G-nad3、nad5-trn H-nad4-nad4L、nad6-cob and nad1-trn L1-rrn L).(3)The frequency of gene rearrangements in the basal lineages of Hymenoptera was found to be the most frequent region near the A-T enrichment region.In addition,even for groups with extremely high species diversity,the degree of gene rearrangement does not change with increased diversity of species.(4)In non-Aportia,a large number of mitochondrial genomes with the same sequence of genes were found in distant lineages.When we take more samples of the lineages between distant taxa,we can see that similar rearrangements come from different evolutionary paths by deducing the evolutionary events of rearrangements.Limited by a lack of understanding of the mechanism,it is too early to identify the convergence.(5)By examining the selection pressure on protein-coding genes near highfrequency rearrangement regions,we found that the entire gene followed neutral evolution,but specific regions have undergone positive selection in favor of amino acid diversity during evolution,indicating that different protein domains with different structures and functions are subject to a different selection.(6)In this study,two methods were used to reconstruct the ancestral state of the basal lineages of Hymenoptera.Tree REx was found to be more complex than Maximum parsimony in inferring rearrangements of historical events,and the derived ancestor state is not reliable.In terms of data entry,Tree REx’s evolutionary model is incomplete.At present,there is no algorithm to search for all possible solutions and ensure the most accurate and minimal reconstruction.It is necessary to improve the existing algorithm,extract,quantify,trace,and deduce the evolutionary history of mitogenomic gene order,which will share data for understanding the macro-evolution of animals,and provide a reference for elucidating the general law of macro-evolution.(7)In the basal lineages of Hymenoptera,more rearrangement events and gene rearrangement patterns were detected,the gene arrangement sequence in each branch has certain randomness,suggesting that mitochondrial gene order does not seem to be useful for higher-order relationships.But in lower-order relationships between Hymenoptera,such as subfamilies and genus,the mitogenomic gene order can be used as a good phylogenetic signal to support the phylogenetic relationship. |
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