Study On Mate Choice And Reproductive Fitness In The Yellow-rumped Flycatcher(Ficedula Zanthopygia)

Mate choice is an important evolutionary process influencing a vast array of traits and ecological processes,which contains both direct and indirect benefits.Extra-pair paternity is widespread among avian species,which is considered to be a means by which females can modify their initial mate choice.The underlying causes of these extrapair matings are not well understood despite being a source of much recent study and debate.The yellow-rumped flycatcher(Ficedula zanthopygia),a sexually dimorphic songbird exhibiting social monogamy with a considerable level of EPP was used as model species.Present study was conducted during breeding seasons from(April-July)2011 to 2013 at Zuojia Nature Reserve.In present study we aimed to test the effect of mate choice and extra-pair mate choice on fitness in yellow-rumped flycatcher.We collected blood samples and morphological measurements of 64 pairs of parents and 325 offsprings.In present study we aimed at unveiling the mechanisms of mate choice at 10 pairs of neutral markers(microsatellites)and MHC genes(adaptive genetic markers)to analyse the microsatellite marker heterozygosity.We checked relateness between the pairs,and compared MHC marker diversity,similarity and amino acid distance between the pairs.The study of the mate choice found that the MHC similarity between the social pairs are lower than random pairs.Females tend to chooseoptimum number of MHC alleles males,which support optimum hypothesis.The study of the extra-pair mate choice found that female yellow-rumped flycatchers are more likely to choose larger and relatively highly heterozygous and less MHC similarity males than their social mates as extra-pair mates.Similarly genetic similarity of pairs that produced mixed-paternity offspring did not differ from the similarity of pairs producing only within-pair offsprings.Further there is no effect of the interaction between male and female MHC allelic diversity on the occurrence of extra-pair paternity(EPP).These findings support the good genes hypothesis but do not exclude the compatibility hypothesis.Present study of MHC loci support for his optimal outbreeding hypothesis.The effect of ecological factors on EPP found that breeding density,breeding synchrony and their interaction did not affect the occurrence of extra-pair paternity in this species.Our results showed that most males were cuckolded by distant males rather than nearest neighbors.In addition,the cuckolders were significant more heterozygous and larger than males they cuckolded.However,no differences were detected between males being cuckolded and their nearest neighbors.These findings indicated that male yellow-rumped flycatchers could prevent from being cuckolded by their nearest neighbours by reducing social mate's willingness via quality-dependent nearest neighbour selection.Quality-dependent nearest neighbour selection might be a cryptic male paternity assurance strategy but still it needs further investigation.The results of analysis on offspring fitness showed that that extra-pair offspring were more heterozygous than their half-siblings,which consist with ‘indirect benefit hypothesis'.Our survey revealed that the sexual strain showed female-biased sex ratios but no evidence for a male-bias in EPO sex ratios.However,females may manipulate the sex ratio of their offspring according to their own condition.