Maternal effects as drivers of sibling competition in a parent–offspring conflict context? An experimental test
Thomas Merkling, Charlotte Perrot, Fabrice Helfenstein, Jean-Baptiste Ferdy, Laurent Gaillard, Emilie Lefol, Emmanuelle Voisin, Scott A. Hatch, Etienne Danchin & Pierrick Blanchard
| Résumé |
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. |
| Mots-clés |
Brood reduction, benefit/cost ratio, facultative siblicide, food availability, phenotypic plasticity, yolk testosterone |
| Citation | Merkling, T., Perrot, C., Helfenstein, F., Ferdy, J. B., Gaillard, L., Lefol, E., Voisin, E., Hatch, S. A., Danchin, E., & Blanchard, P. (2016). Maternal effects as drivers of sibling competition in a parent–offspring conflict context? An experimental test. Ecology and Evolution, 6, 3699-3710. |
| Type | Article de périodique (Anglais) |
| Date de publication | 3-5-2016 |
| Nom du périodique | Ecology and Evolution |
| Volume | 6 |
| Pages | 3699-3710 |