The Influence Factors Of Extra-pair Mate Choice In Female Great Tit(Parus Major)

In monogamous birds,female copulate with the male outside of social spouse is called extra-pair copulations,the offspring called extra-pair offspring.Monogamy is divided into social monogamy and genetic monogamy.Theoccurrence ofextra-paircopulationsandtheinfluencehasbecomethefocus researches in the behavioral ecology of avian species.The researchers carried out a large number of studies on the mechanism of the occurrence and distribution of birds,but there is no conclusive evidence about the influence factors of extra-pair.Great tits(Parus major)are social monogamous,secondary cavity-nesting birds.It has been proved that there is extra-pair phenomenon in great tits.This study during March to July in 2014 to 2016 at Zuo Jia Natural Reserve Jilin province.The purpose of this study was to determine the proportion of extra-pair in the target population,to explore and analyze the influencing factors of extra-pair and the morphological and behavioral characteristics of extra-pair partner.During the study period,we caught 73 pairs of great tits during their first brood,collected total parent-offspring blood samples and measured morphological characteristics,and recorded 49 males' territorial song.We identify extra-pair paternity by microsatellite marker methods,and the result of molecular experiment was analyzed through Cervus3.0 software,COANCESTRY software and SPSS21.0 software.The results showed that :There are 35.61%(26/73)nest have EPO.There are 9.28%(77/829)offspring is EPO.In the nest with EPO,There are 28%(77/275)chicks were EPO.There were no significant differences between EPO and non EPO male morphological features,singing characteristics,that female may not according to morphological characteristics of male spousesoutside marriage.There were no significant differences on genetic heterozygosity between ThemaleshaveandnothavetheEPYinnest(Z=-1.493,p=0.135).The genetic heterozygosity of the social males they cuckolded was significantly lower than that of the extra-pair males(Z=-2.425,p=0.021),there were nosignificant differences on genetic heterozygositybetween the EPY and WPY(Z=-1.323,p=0.186).Females in choosing extra-pair males,not choose high genetic heterozygosity males in the population(W=-1.0309,p=0.3091).The results indicate that male genes heterozygosity was not the main motivation for female occur extra-Pair copulations;female preference choice extra-pair males with higher genetic heterozygosity than their social males,but that cannot increase their offspring heterozygosity.Pairwise relatedness of the males have the EPY in nest is significantly higher than that of the males not have EPY in nest(t=2.237,p=2.237).The pairwise relatedness betweensocial males are significantly higher than extra-pair males(t=4.430,p<0.001).The results indicate that the pairwise relatedness of society pairs are the influence factores for extramarital.The female preference selection the lower pairwise relatedness than herself as the partner extramarital.