Ecological correlates of fitness across the northern geographic range limit of a Pacific Coast dune plant
Bibliographic record
Abstract
A species is expected to occur where the prevailing biotic and abiotic conditions fall within its fundamental niche. Geographic range limits should, therefore, occur when the survival and fitness of individuals along ecological gradients is reduced to the point at which populations are no longer self-sustaining. Abrupt limits to a species' distribution are expected to reflect abrupt changes in the ecological conditions that cause sharp declines in fitness across the limit. We investigated the correlation between geographic variation in environment and fitness across the abrupt northern range limit of a coastal dune plant, Camissoniopsis cheiranthifolia (Onagraceae). In each of 64 plots distributed across five sites along a 200-km transect spanning the species' northern range limit (four within the range plus one beyond the limit), we measured plant community composition as a proxy for variation in biotic and abiotic environmental factors and lifetime fitness of genetically standardized experimental populations of C. cheiranthifolia. There was substantial variation in plant community composition among plots and sites across the range limit, and fitness of experimental plants covaried strongly with the first principal component of plant community composition. However, we did not detect an abrupt shift in plant community or the expected decline in fitness across the range limit. In fact, fitness and recruitment increased toward the limit and were relatively high beyond the limit. This suggests that habitat beyond the range did not occur outside of the species' fundamental niche. These results challenge niche-based explanations for range limits and suggest that hypotheses involving the finer-scale distribution of habitat patches or constraints on dispersal warrant more serious consideration.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".