Lower elevation animal species do not tend to be better competitors than their higher elevation relatives
Bibliographic record
Abstract
Abstract Aim What factors set species' range edges? One general hypothesis, often attributed to Darwin and MacArthur, is that interspecific competition prevents species from inhabiting the warmest portions along geographic gradients (i.e., low latitudes or low elevations). A prediction arising from this Darwin–MacArthur hypothesis is that lower elevation species are better competitors than related higher elevation species. An alternative prediction is that higher elevation animal taxa will tend to be better competitors because they will tend to be larger (Bergmann's rule). Here, I test these opposing predictions. Location Global. Time period 1971–2019. Major taxa studied Birds, mammals, amphibians, fishes. Methods I conducted a meta‐analysis of studies that measured pairwise behavioural aggression between species‐pairs of closely related animals where the two species inhabit divergent elevational distributions. Results I found that (a) interspecific aggression appears to be a reliable indicator of interspecific competition; (b) elevational position was not consistently linked to interspecific aggression—while lower elevation songbird species in the tropics showed stronger interspecific aggression in response to playback experiments, higher elevation species showed stronger interspecific aggression in direct observations of interspecific aggression across a range of taxa and latitudes; (c) body size was a good predictor of pairwise interspecific aggression and (d) there was limited evidence for Bergmann's rule. Main conclusions My results do not support the longstanding prediction that lower elevation animals are generally better competitors than their higher elevation relatives. Instead, patterns of interspecific aggression are linked to body size, with larger animals showing more aggression towards smaller relatives than vice versa. Hence, a trait—body size—that is idiosyncratically related to elevational position appear to determine the outcome of pairwise behavioural interactions. Last, I consider these results in the context of the hypothesis that behavioural interactions may impact rates of upslope range shifts associated with recent warming.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".