Role of the host plant in the decline of populations of a specialist herbivore, the spruce bud moth
Bibliographic record
Abstract
Summary 1. The following three hypotheses explaining why spruce bud moth (Zeiraphera canadensis Mut. and Free.) populations decline at crown closure were evaluated: (i) first‐instar larval mortality increases as a result of asynchrony between budburst and egg hatch (phenology hypothesis); (ii) larval mortality increases and fecundity of females decreases due to decreased nutritional quality of shaded foliage (nutrition hypothesis); and (iii) egg densities decrease because females lay fewer eggs in closed stands (oviposition preference hypothesis). 2. Field experiments and surveys supported the phenology and oviposition preference hypotheses but not the nutrition hypothesis. 3. Increases in the degree of asynchrony between the time of egg hatch and budburst following increased shading of tree crowns resulted in high mortality of first instars in closed stands. 4. In closed stands budburst was delayed because snow cover reduced soil and root temperatures when air temperatures were above the minimum threshold for egg development. Consequently, many eggs (which are located in the crown) hatched before buds burst. 5. Decreases in larval survival following crown closure were not attributable to changes in the nutritional quality of shaded foliage for larval development and did not influence adult sex ratios in 2 of 3 years. 6. Females that developed on closed or open trees were of similar size, indicating that declines in population density following crown closure were not due to reduced fecundity. 7. When trees in a closed stand were opened by removing nearby trees, they were subjected to higher levels of herbivory. Egg hatch was more closely synchronized with budburst on opened than on closed trees. 8. We conclude that declines in bud moth populations following crown closure are caused by increased first‐instar larval mortality, resulting from temporal asynchrony between budburst and egg hatch, and reduced oviposition caused by female preference for open trees.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".