Mitochondrial Genomics And Phylogeny Of Five Species Of Philopteridae

Philopteridae is a family of tiny parasitic lice with a history of incomplete metamorphosis consisting of egg,nymph and adult.It is only parasitic on the body surface of birds,and feeds on host feathers,fluff,dander,scales and skin secretions.When large numbers of feathered lice colonize the host,they cause diseases,spread avian diseases,and even lead to host death.Mitochondrial genome is characterized by matrilineal inheritance,conservative gene arrangement,stable structure,fast evolution rate and relatively short in length,so it is an ideal molecular marker for studying phylogeny.There are many species in Philopteridae,and the internal phylogenetic relationship is complex.Moreover,the fragmentation of mt genome and mt gene rearrangement are common phenomena in parasitic lice.However,we rarely get full mt genomes from Philopteridae,the most species-rich member of Ischnocera.At present,only 9 mt genomes of Philopteridae have been detected.Therefore,sequencing and parsing more Philopteridae mt genomes is of great significance for further revealing gene structural characteristics and internal phylogenetic relationships of Philopteridae mt genes.（1）In this study,Next-generation sequencing,assembly,annotation and comparative analysis were carried out on the mt genomes of 5 species in Philopteridae,and the number of mt genomes measured in this family reached 14 species.The mitochondrial genome structure of Falcolipeurus suturalis,Anatoecus dentatus and Anaticola crassicornis is a complete large ring（16,659 bp,14,270 bp,14,629 bp）.The mitochondrial genomes of Ibidoecus plataleae and Goniodes dissimilis are divided into 12-13 small rings with 2 KB-4 KB in length.The content of A+T ranged from 62.1%-76.2%.All the Philopteridae had positive GC-skew,the highest was 18.9%for F.suturalis and the lowest was 1.5%for A.dentatus It is proved that the asymmetry of base composition exists in the mt genome within the Philopteridae,and there is also a division phenomenon..（2）Among the mitochondrial genomes of the five species of Philopteridae.Each species has a small portion of the protein-coding gene using an incomplete stop codon T or TA.Some tRNAs of A.crassicornis,G.dissimilis and I.Plataleae were duplicated.The D-arm is absent in the secondary structure of tRNA-Ala and tRNA-Ser^AGN of A.dentatus,and tRNA-Ala of G.Dissimilis.Mitochondrial genes were rearranged in all Philopteridae compared to the putative insect mitochondrial ancestor karyotype.In general,the mitochondrial gene arrangement between parasitic lice of the same genus is very conservative.However,in this experiment,we changed the interspecific mitochondrial gene arrangement and structure of two parasitic lice species of Falcolipeurus and two parasitic lice species of Ibidoecus.The results suggested that there was a widespread gene rearrangement in the genome of Philopteridae,and the gene sequences were not conserved within the genus.（3）In this study,we constructed an evolutionary tree by adopting two methods,Bayesian method（BI）and maximum likelihood method（ML）and using the complete mitochondrial genome of 14 species of Philopteridae.In these two trees,F.quadripustulatus and F.suturalis were clustered into a single branch,A.crassicornis and A.dentatus were clustered into a single branch,and all were closely related to the genus Falcolipeurus.It wasnot consistent with previous studies revealing that Falcolipeurus and Ibidoecus are closelyrelated.Phylogenetic analysis showed that F.quadripustulatus and F.suturalis;the genetic differences between I.bisignatus and I.Plataleae within the genus were significant（Bpp=1.0;Bf=100）.In addition,the results based on bayesian and maximum likelihood methods support the monophyletic group of Philopteridae,providing new insights into the phylogenetic relationships in Philopteridae.This study not only provided a new molecular marker for species identification of Philopteridae,but also proved the cracking phenomenon of mitochondrial genome of each genus of Philopteridae.The diversity and evolution of mitochondrial genome structure of some genera in the family were also elucidated,which provided new data support for futher analysis of the phylogenetic family relationship.