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Maternal effects as drivers of sibling competition in a parent-offspring conflict context? An experimental test.

ABSTRACT: Maternal effects occur when the mother's phenotype influences her offspring's phenotype. In birds, differential allocation in egg yolk components can allow mothers to compensate for the competitive disadvantage of junior chicks. We hypothesize that the parent-older chick conflict peaks at intermediate conditions: parents benefit from the younger chick(s) survival, but its death benefits the older chick in terms of growth and survival. We thus expect maternal compensation to follow a bell-shaped pattern in relation to environmental conditions. We studied a black-legged kittiwake (Rissa tridactyla) population where previous results revealed increased allocation of yolk testosterone in younger as compared to older chicks in intermediate conditions, in line with our theoretical framework. We therefore predicted a maternally induced increase in aggressiveness, growth, and survival for younger chicks born in intermediate environmental conditions. Controlling for parental effects and chick sex, we manipulated food availability before egg laying to create a situation with intermediate (Unfed group) and good (Fed group) environmental conditions. Within each feeding treatment, we further created experimental broods where the natural hatching order was reversed to maximize our chances to observe an effect of feeding treatment on the younger chicks' aggressiveness. As predicted, we found that chick aggressiveness was higher in younger chicks born from the Unfed group (i.e., in intermediate environmental conditions), but only when they were put in a senior position, in reversed broods. Predictions on growth and survival were not confirmed. Mothers thus seem to favor the competitiveness of their younger chick in intermediate conditions via egg yolk components, but our study also suggests that hatching asynchrony need to be small for maternal compensation to be efficient. We emphasize the need for further studies investigating other chick behaviors (e.g., begging) and focusing on the relative role of different yolk components in shaping parent-offspring conflict over sibling competition.

SUBMITTER: Merkling T

PROVIDER: S-EPMC5513303 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Maternal effects as drivers of sibling competition in a parent-offspring conflict context? An experimental test.

Merkling Thomas T Perrot Charlotte C Helfenstein Fabrice F Ferdy Jean-Baptiste JB Gaillard Laurent L Lefol Emilie E Voisin Emmanuelle E Hatch Scott A SA Danchin Etienne E Blanchard Pierrick P

Ecology and evolution 20160503 11

Maternal effects occur when the mother's phenotype influences her offspring's phenotype. In birds, differential allocation in egg yolk components can allow mothers to compensate for the competitive disadvantage of junior chicks. We hypothesize that the parent-older chick conflict peaks at intermediate conditions: parents benefit from the younger chick(s) survival, but its death benefits the older chick in terms of growth and survival. We thus expect maternal compensation to follow a bell-shaped ...[more]

PMID: 28725354

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Project description:OBJECTIVE:To study the impact of maternal smoking during pregnancy on fractures in offspring during different developmental stages of life. DESIGN:National register based birth cohort study with a sibling comparison design. SETTING:Sweden. PARTICIPANTS:1?680?307 people born in Sweden between 1983 and 2000 to women who smoked (n=377?367, 22.5%) and did not smoke (n=1?302?940) in early pregnancy. Follow-up was until 31 December 2014. MAIN OUTCOME MEASURE:Fractures by attained age up to 32 years. RESULTS:During a median follow-up of 21.1 years, 377?970 fractures were observed (the overall incidence rate for fracture standardised by calendar year of birth was 11.8 per 1000 person years). The association between maternal smoking during pregnancy and risk of fracture in offspring differed by attained age. Maternal smoking was associated with a higher rate of fractures in offspring before 1 year of age in the entire cohort (birth year standardised fracture rates in those exposed and unexposed to maternal smoking were 1.59 and 1.28 per 1000 person years, respectively). After adjustment for potential confounders the hazard ratio for maternal smoking compared with no smoking was 1.27 (95% confidence interval 1.12 to 1.45). This association followed a dose dependent pattern (compared with no smoking, hazard ratios for 1-9 cigarettes/day and ?10 cigarettes/day were 1.20 (95% confidence interval 1.03 to 1.39) and 1.41 (1.18 to 1.69), respectively) and persisted in within-sibship comparisons although with wider confidence intervals (compared with no smoking, 1.58 (1.01 to 2.46)). Maternal smoking during pregnancy was also associated with an increased fracture incidence in offspring from age 5 to 32 years in whole cohort analyses, but these associations did not follow a dose dependent gradient. In within-sibship analyses, which controls for confounding by measured and unmeasured shared familial factors, corresponding point estimates were all close to null. Maternal smoking was not associated with risk of fracture in offspring between the ages of 1 and 5 years in any of the models. CONCLUSION:Prenatal exposure to maternal smoking is associated with an increased rate of fracture during the first year of life but does not seem to have a long lasting biological influence on fractures later in childhood and up to early adulthood.

Dataset Information

Maternal effects as drivers of sibling competition in a parent-offspring conflict context? An experimental test.

Publications

Maternal effects as drivers of sibling competition in a parent-offspring conflict context? An experimental test.

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