Effects Of Haemosporidium Infection And MHC Class? Allele Polymorphism On Double Brooding Strategy Of Great Tit (Parus Major)

Double brooding is a common strategy for many birds to increase their reproductive output.However,since the breeding behavior of birds will increase their own energy consumption,and the secondary breeding will undoubtedly cost more.Therefore the relevant factors such as the physical condition of birds and the investment in breeding may affect the double brooding decision of birds to different degrees.As one of the important factors affecting the health of birds,hemosporidium parasitises in the host and exerts severe selection pressure on the host by using the host's resources.Highly polymorphic MHC genes play an important role in immune response,and MHC class? genes are often associated with parasitic infections,and changes in their polymorphism may influence the breeding decisions of birds.At present,there are many studies on the relationship between haemosporidium infection or MHC allele polymorphism with bird reproduction,but no studies have shown the relationship between them with bird' double brooding.In this study,the great tit?Parus major?,a typical small passerine bird with double brooding,was taken as the research object.In 2018-2019,field surveys were conducted in Zuojia nature reserve of Jilin province from May to July each year,and a total of 290 blood samples and body indicators of great tits were collected.Nested PCR was used to determine the status of haemosporidia infection in individuals of great tit,and the infected haemosporidia species were identified using Malavi database.Meanwhile,high-throughput sequencing technology was used to determine the MHC class? allele sequence of great tit,and then genotyping was performed.Our aim was to investigate the effects of haemosporidium infection and the number of MHC class? alleles on double brooding of great tit:?1?Of the 290 captured great tits,76 were infected with hemosporidia?positive samples?,with an overall infection rate of 26.1%.The results of binomial test showed that the number of infected males was significantly higher than that of females?n = 76,p = 0.02?.Of the 76 positive samples,73 were successfully identified as haemoproteus spore lineage,including 1 Haemomoeba lineage?prevalence 2.7%?,2 Plasmodium lineages?prevalence 22.8%?,and 3 individuals infected with Leucocytozoon?prevalence 1%?,but no corresponding lineages were found in the Malavi database.?2?The reproductive success rate of infected individuals was 84%,higher than that of uninfected individuals?78.7%?and higher than that of population?80.1%?.In addition,independent sample T test and BH correction of p value show,infected and uninfected individuals had no significant difference in tarsus length(t =-0.523,p_adj = 0.610),body length(t =-1.881,p_adj = 0.122),body weight(t =-0.511,p_adj = 0.610),and middle toe length(t =-1.411,p_adj = 0.239),but there was a significant difference in wing length(t =-2.686,p_adj = 0.024)and tail length(t =-3.824,p_adj = 0.000),indicating that individuals with longer wings and tails were more likely to be infected with haemosporidium.?3?After high-throughput sequencing and genotyping of 290 great tits,594 MHC class? alleles were identified.The average number of alleles identified by each individual was 24.7 ± 6.446?mean ± standard deviation,the same below?.Among them,the average number of alleles with and without secondary propagation was 24.69 ± 5.983 and 24.74 ± 7.686,respectively?p = 0.970?.Pearson correlation analysis revealed no significant difference between the number of MHC class? alleles and physical signs.The overall nucleotide polymorphism of the MHC class? allele was 0.10837.In addition,by analysis of the generalized linear mixture model,the number of alleles of MHC class??GLMMs: ?² = 0.1409,df = 1,p = 0.7074?and hemosporidium infection?GLMMs: ?² = 1.3785,df = 1,p = 0.7978?had no significant effect on the double brooding of great tit.In conclusion,the infection rate of hemosporidia was higher in males than in females of the great tit population in Zuojia area,suggesting that sex may be related to hemosporidia infection,and individuals with good physical conditions are more likely to be parasitized by hemosporidia.However,hematosporidium infection and the number of MHC class? alleles were not associated with double brooding of great tits,which suggested that they may not affect double brooding of great tits.