The Relationships Of Reproductive Performance With Oxidative Stress And Parasite Infection In Varied Tit(Sittiparus Varius)

Reproductive is a costly link to birds'life-history and a key field of bird ecology research.According to the basic concept of life-history trade-off,organisms have to trade-off between current breeding with future breeding also survival.Different body conditions of birds may lead to various reproductive strategies.High-quality individuals will perform better in coping with the adverse environment,getting and assigning resources,so they had higher reproductive fitness.Oxidative stress and parasitism are important physiological factors that reflect birds'physiology condition.Oxidative stress is a physiological adaptation mechanism that individuals cope with internal and external stimulation,and a critical physiological factor mediates birds'reproductive improvement strategies.Blood parasite is a global natural stressor of wild birds,they use the resource of hosts for growth and reproduction and cause host fitness reduced.Parasitism is gradually being accepted as the major selective force affecting avian life histories.In this study,we took a blood sample from Varied Tit in the wild field during their early brooding period(6-8 days post-hatching),who bred in artificial nests.Then we measured the levels of plasma oxidative stress(reactive oxygen species,ROS and superoxide dismutase,SOD concentration)and parasitic infection status.We also got the reproductive parameters of Varied Tit by nest monitoring.To explore the adjustment of birds'physiological status to their reproductive strategies,partial least squares regression(PLS)analysis was used to analyze the relationship between reproduction performance and oxidative stress,and the relationship between reproduction performance and parasitism.The main results are as follows:1.there was no significant difference between the reactive oxygen species and superoxide dismutase of the male and female Varied Tit in the early brooding period(reactive oxygen species:t_20,25=-0.887,P=0.380;superoxide dismutase:t_20,25=-1.325,P=0.192).2.12 among 25 male Varied Tits and 12 among 23 female Varied Tits were tested positive for parasites.There was no significant difference between parasitic infected and no parasitic infection of oxidative stress(female:reactive oxygen species:t_8,11=-0.173,P=0.864;superoxide dismutase:t_8,11=1.421,P=0.174;male:reactive oxygen species:t_13,12=-0.510,P=0.615;superoxide dismutase:t_13,12=0.619,P=0.542).3.Parasitism significantly reduced the reproductive effort of male Varied Tit(?=-0.598,P=0.018),while parasitism was not related to feeding quantity(?=0.217,P=0.564),and not related to the body mass of offspring in 8 days post-hatching(?=-0.398,P=0.283).And in female Varied Tit,there was no statistical significance between parasitism and reproductive effort(?=-0.052,P=0.906),also feeding quantity(?=0.242,P=0.618)and the body mass of offspring in 8 days post-hatching(?=0.702,P=0.055).Biomarkers of oxidative stress were not related to the feeding quantity of Varied Tit(female:reactive oxygen species:?=-0.732,P=0.185;superoxide dismutase:?=0.553,P=0.411;male:reactive oxygen species:?=0.17,P=0.823;superoxide dismutase:?=-0.167,P=0.839).Biomarker of oxidative stress was not related to the body mass of offspring in 8 days post-hatching(female:reactive oxygen species:?=-0.316,P=0.409;superoxidedismutase:?=0.049,P=0.921;male:reactive oxygen species:?=0.075,P=0.858;superoxide dismutase:?=0.088,P=0.821),and not related to the reproductive effort(female:reactive oxygen species:?=-0.576,P=0.477;superoxide dismutase:?=0.327,P=0.187;male:reactive oxygen species:?=0.183,P=0.755;superoxide dismutase:?=0.021,P=0.975).4.There was no significant correlation between parasitism and fledging rate of offspring(female:?=0.388,P=0.174;male:?=-0.492,P=0.149)and breeding success in Varied Tit(female:?=0.314,P=0.349;male:?=-0.442,P=0.153).Reactive oxygen species of female Varied Tit was significantly negatively correlated with the fledging rate(?=-1.238,P=0.009),and it's significantly negatively correlated with breeding success(?=-1.262,P=0.006).There was no significant correlation between oxidative stress and fledging rate(reactive oxygen species:?=0.225,P=0.717;superoxide dismutase:?=-0.181,P=0.826),and there was no significant correlation between oxidative stress and breeding success in male Varied Tit(reactive oxygen species:?=-0.112,P=0.879;superoxide dismutase:?=0.124,P=0.883).In summary,Parasitism showed adverse effects on parental investment of the brooding period,but it sex-specific.Parasitism reduced the reproductive effort of male Varied Tit but didn't affect the reproductive success;Oxidative stress(reactive oxygen species)didn't significantly affect the parental investment of Varied Tit but significantly predicted its reproductive success,female Varied Tit with a high concentration of reactive oxygen species will reproductive success decline.