| Wolbachia,known as an intracellular symbiont that has the same genetic pattern as mitochondrial DNA(mt DNA)follows,is widely detected in insects.The transmission pathway of its maternal inheritance will affect the genetic diversity of the hosts’ mt DNA,which makes it difficult for using mt DNA to accurately reflect the infection of the host for population genetic structure study and species classification,etc.In the previous studies of the Wolbachia in butterflies,there has not been a systematic report on analyzing at "genus" level as the classification unit.It is hard to evaluate the error when making a systematic evaluation of the interaction between Wolbachia and its butterfly hosts’ mitochondrial DNA.In this study,204 samples were used from 17 species of Polytremis.Firstly,the infection of Wolbachia in those samples were detected,the correlation analysis between environmental climate and Wolbachia infection rate in Polytremis was performed considering the influences by geographical distribution.The Polytermis mt DNA haplotypes network was constructed,multiple phylogenetic trees were also constructed with both nuclear and mitochondrial genes,as well as multi-locus sequence typing fragments of Wolbachia.The genetic diversity in different strains of Wolbachia together with their hosts’ genes was discussed under these analysis.After performing the analysis mentioned above,we got some conclusions at the classification unit as “genus” in this study: 1)a total of 6 species of Polytremis were found to be infected with Wolbachia,34%(70/204)of the samples from the Polytremis were tested as Wolbachia positive.Three strains of Wolbachia were divided using wsp primer,which were named as w Nas1,w Nas2 and w Nas3 respectively in this study.Furthermore,it can also be divided into six types(ST-19,ST-474 to ST-478)by multi-locus sequence typing(MLST).Combined with the distribution information of the samples’ collected locations,we draw a conclusion that the infection rate of Wolbachia in southeastern China is higher than that in the centraland western regions,and it may be related to the influences of temperature differences etc.2)Based on the comparison of the divergent time between Wolbachia and Polytremis,we speculate that Wolbachia detected in Polytremis should spread mainly through the horizontal direction,not by the vertical transmission.3)At the intraspecies level,we found that w Nas1 is associated with a reduction in mitochondrial gene polymorphism in the infected population.But within the interspecies level,there is an inconsistency between mt DNA and the nuclear genes,which may due to the mt DNA gene introgression from P.fukia into P.nascens influenced by the infections of w Nas3.Furthermore,this study did not detect a male individual infected with the w Nas2 strain of Wolbachia.We speculate that this strain –w Nas2 will mediate its hosts’ male-killing or host feminization.But this speculation requires larger scale collection and further experiments to verify.Based on the analysis of the genetic data used in this study,the pattern of the dynamic symbiotic interaction between Polytremis and Wolbachia on mt DNA was discussed,which provided a reference for the further studies in Wolbachia infections and its influence in butterfly populations on structure and phylogenetic development. |
