Oxidative status and reproductive effort of great tits in a handicapping experiment

Father's contribution in child care matters. Using an experimental approach, we showed that handicapped great tit fathers are more likely to reduce investment in their offspring compared with control fathers. In contrast, handicapped mothers did not reduce investment in their offspring. Furthermore, cellular stress levels differed between males and females, supporting the idea that males and females follow different lifetime strategies when it comes to the trade-off between self-maintenance and reproductio

Parasites suppress immune-enhancing effect of methionine in nestling great tits

After birth, an organism needs to invest both in somatic growth and in the development of efficient immune functions to counter the effects of pathogens, and hence an investment trade-off is predicted. To explore this trade-off, we simultaneously exposed nestling great tits (Parus major) to a common ectoparasite, while stimulating immune function. Using a 2×2 experimental design, we first infested half of the nests with hen fleas (Ceratophyllus gallinae) on day 3 post-hatch and later, on day 9-13 post-hatch, and then supplemented half of the nestlings within each nest with an immuno-enhancing amino acid (methionine). We then assessed the non-specific immune response by measuring both the inflammatory response to a lipopolysaccharide (LPS) and assessing the levels of acute phase proteins (APP). In parasite-infested nestlings, methionine had a negative effect on body mass close to fledging. Methionine had an immune-enhancing effect in the absence of ectoparasites only. The inflammatory response to LPS was significantly lower in nestlings infested with fleas and was also lower in nestlings supplemented with methionine. These patterns of immune responses suggest an immunosuppressive effect of ectoparasites that could neutralise the immune-enhancing effect of methionine. Our study thus suggests that the trade-off between investment in life history traits and immune function is only partly dependent on available resources, but shows that parasites may influence this trade-off in a more complex way, by also inhibiting important physiological functions

Data from: Heterozygosity is linked to the costs of immunity in nestling great tits (Parus major)

There is growing evidence that heterozygosity–fitness correlations (HFCs) are more pronounced under harsh conditions. Empirical evidence suggests a mediating effect of parasite infestation on the occurrence of HFCs. Parasites have the potential to mediate HFCs not only by generally causing high stress levels but also by inducing resource allocation tradeoffs between the necessary investments in immunity and other costly functions. To investigate the relative importance of these two mechanisms, we manipulated growth conditions of great tit nestlings by brood size manipulation, which modifies nestling competition, and simultaneously infested broods with ectoparasites. We investigated under which treatment conditions HFCs arise and, second, whether heterozygosity is linked to tradeoff decisions between immunity and growth. We classified microsatellites as neutral or presumed functional and analyzed these effects separately. Neutral heterozygosity was positively related to the immune response to a novel antigen in parasite-free nests, but not in infested nests. For nestlings with lower heterozygosity levels, the investments in immunity under parasite pressure came at the expenses of reduced feather growth, survival, and female body condition. Functional heterozygosity was negatively related to nestling immune response regardless of the growth conditions. These contrasting effects of functional and neutral markers might indicate different underlying mechanisms causing the HFCs. Our results confirm the importance of considering marker functionality in HFC studies and indicate that parasites mediate HFCs by influencing the costs of immune defense rather than by a general increase in environmental harshness levels

Single locus heterozygosity

Single locus heterozygosity for all individual nestlings. 0=homozygous, 1=heterozygous

Body measures and heterozygosity levels

This data set includes nestling body measures and heterozygosity levels of nestlings and rearing parents. Nest_ID: Nest of rearing, Chick_ID: Individual nestling's code, Brood_manipul: Brood size manipulation treatment, Infestation: Flea infestation, Original_brood: Brood size before manipulation treatment, HetHLm(f)_f: Functional heterozygosity of foster male (female), HetHLm(f)_n: Neutral heterozygosity of foster male (female), HetHL_f: Nestling functional heterozygosity, HetHL_n: Nestling neutral heterozygosity, Sex: Nestling sex, Weight_d15: Nestling weight 15 days after hatching, Fledged: 1=nestling successfully fledged, 0= nestling died, LPS_response: Difference in thickness measure before and after LPS-Injection, Rank: Nestling hatching rank, Body_cond: Nestling body conditio

Body measures and heterozygosity levels

This data set includes nestling body measures and heterozygosity levels of nestlings and rearing parents. Nest_ID: Nest of rearing, Chick_ID: Individual nestling's code, Brood_manipul: Brood size manipulation treatment, Infestation: Flea infestation, Original_brood: Brood size before manipulation treatment, HetHLm(f)_f: Functional heterozygosity of foster male (female), HetHLm(f)_n: Neutral heterozygosity of foster male (female), HetHL_f: Nestling functional heterozygosity, HetHL_n: Nestling neutral heterozygosity, Sex: Nestling sex, Weight_d15: Nestling weight 15 days after hatching, Fledged: 1=nestling successfully fledged, 0= nestling died, LPS_response: Difference in thickness measure before and after LPS-Injection, Rank: Nestling hatching rank, Body_cond: Nestling body conditio