When anthropogenic‐related disturbances overwhelm demographic persistence mechanisms
Bibliographic record
Abstract
Summary Population decline is associated with increased vulnerability to extinction, but also with possible density‐, frequency‐ or distance‐related ‘rarity advantages’ that increase recruitment success as individuals become isolated from their congeners. Distinguishing between these alternatives (risk vs. recovery of rare populations via demographic processes) has become critical, given how anthropogenic disturbances are causing population declines globally. Here, we demonstrate how distance‐related rarity advantages are evident in spatially isolated recruits of a canopy‐dominant but regionally rare species of oak that appears to be suffering recruitment collapse. As distance from parent trees increased, seedlings had significantly more leaves and experienced reduced insect browsing and intraspecific competition. Long‐term field‐based experimental treatments revealed these advantages to be associated with rapid rates of juvenile maturation and survival that are unobserved in natural settings. The discrepancy between the experimental and natural settings was explained by trophic collapse and habitat loss – two changes ubiquitous to many terrestrial ecosystems – that combine to concentrate vertebrate herbivores in habitat remnants and cause 100% juvenile mortality via the browsing of taller juveniles. Exotic grass cover, long associated with oak recruitment failure, significantly suppressed seedling height and leaf production, but appeared to delay mortality by hiding shorter seedlings from vertebrate herbivores. Synthesis. Our work demonstrates how rarity advantages have the potential to positively influence the population performance of a declining species, but are short‐circuited by intense herbivory associated with human‐based environmental change. Regionally, there appear to be few existing conditions on the contemporary landscape that favour juvenile survival, suggesting ongoing recruitment difficulties without intervention. Our work clarifies how extinction risk can in some cases be best defined by how anthropogenic disturbances affect, and are offset by, demographic‐based persistence mechanisms, than simply by present‐day abundance or distribution.
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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 | 0.001 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".