Quantifying capital versus income breeding: New promise with stable isotope measurements of individual amino acids
Bibliographic record
Abstract
Abstract Capital breeders accumulate nutrients prior to egg development, then use these stores to support offspring development. In contrast, income breeders rely on local nutrients consumed contemporaneously with offspring development. Understanding such nutrient allocations is critical to assessing life‐history strategies and habitat use. Despite the contrast between these strategies, it remains challenging to trace nutrients from endogenous stores or exogenous food intake into offspring. Here, we tested a new solution to this problem. Using tissue samples collected opportunistically from wild emperor penguins Aptenodytes forsteri , which exemplify capital breeding, we hypothesized that the stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope values of individual amino acids (AAs) in endogenous stores (e.g. muscle) and in egg yolk and albumen reflect the nutrient sourcing that distinguishes capital versus income breeding. Unlike other methods, this approach does not require untested assumptions or diet sampling. We found that over half of essential AAs had δ 13 C values that did not differ between muscle and yolk or albumen, suggesting that most of these AAs were directly routed from muscle into eggs. In contrast, almost all non‐essential AAs differed in δ 13 C values between muscle and yolk or between muscle and albumen, suggesting de novo synthesis. Over half of AAs that have labile nitrogen atoms (i.e. ‘trophic’ AA) had higher δ 15 N values in yolk and albumen than in muscle, suggesting that they were transaminated during their routing into egg tissue. This effect was smaller for AAs with less labile nitrogen atoms (i.e. ‘source’ AA). Our results indicate that the δ 15 N offset between trophic‐source AAs (Δ 15 N trophic‐source ) may provide an index of the extent of capital breeding. The value of emperor penguin Δ 15 N Pro‐Phe was higher in yolk and albumen than in muscle, reflecting the mobilization of endogenous stores; in comparison, the value of Δ 15 N Pro‐Phe was similar across muscle and egg tissue in previously published data for income‐breeding herring gulls Larus argentatus smithsonianus . Our results provide a quantitative basis for using AA δ 13 C and δ 15 N, and isotopic offsets among AAs (e.g. Δ 15 N Pro‐Phe ), to explore the allocation of endogenous versus exogenous nutrients across the capital versus income spectrum of avian reproduction.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".