Long-term research and hierarchical models reveal consistent fitness costs of being the last egg in a clutch

1. Maintenance of phenotypic heterogeneity in the face of strong selection
is an important component of evolutionary ecology, as are the consequences
of such heterogeneity. Organisms may experience diminishing returns of
increased reproductive allocation as clutch or litter size increases,
affecting current and residual reproductive success. Given existing
uncertainty regarding trade-offs between the quantity and quality of
offspring, we sought to examine the potential for diminishing returns on
increased reproductive allocation in a long-lived species of goose, with a
particular emphasis on the effect of position in the laying sequence on
offspring quality. 2. To better understand the effects of maternal
allocation on offspring survival and growth, we estimated the effects of
egg size, timing of breeding, inter- and intra-annual variation, and
position in the laying sequence on gosling survival and growth rates of
black brent (Branta bernicla nigricans) breeding in western Alaska from
1987–2007. 3. We found that gosling growth rates and survival decreased
with position in the laying sequence, regardless of clutch size. Mean egg
volume of the clutch a gosling originated from had a positive effect on
gosling survival (β = 0.095, 95% CRI: 0.024, 0.165), and gosling growth
rates (β = 0.626, 95% CRI: 0.469, 0.738). Gosling survival (β = -0.146,
95% CRI: -0.214, -0.079) and growth rates (β = -1.286, 95% CRI: -1.435,
-1.132) were negatively related to hatching date. 4. These findings
indicate substantial heterogeneity in offspring quality associated with
their position in the laying sequence. They also potentially suggest a
trade-off mechanism for females whose total reproductive investment is
governed by pre-breeding state. 20-Mar-2020