Periodic invasions during El Niño events by the predatory lined shore crab (<i>Pachygrapsus crassipes</i>): forecasted effects of its establishment on direct-developing indigenous prey species (<i>Littorina</i> spp.)
Bibliographic record
Abstract
Coevolutionary arms races between shelled gastropods and their predators are more escalated near the equator. Therefore, temperate gastropods are predicted to be maladapted to highly specialized tropical shell-crushing crabs. The northern geographical limit of the lined shore crab (Pachygrapsus crassipes J.W. Randall, 1840) does not usually overlap with the southern limit of the Sitka periwinkle (Littorina sitkana Philippi, 1846), which lacks a pelagic larval stage. Large El Niño events increased the winter abundance and poleward transport of P. crassipes larvae from California (USA) in the Davidson Current. Temporary intertidal crab populations that included females with eggs were observed 1–4 years later, >1000 km north of its usual geographical range. Laboratory experiments showed that L. sitkana did not have a size refuge from adult P. crassipes. Moreover, consumption rates of adult L. sitkana by P. crassipes were 10-fold higher than those published for indigenous purple shore crabs (Hemigrapsus nudus (Dana, 1851)) with similar claw sizes. Additionally, the upper intertidal limit of invading P. crassipes was higher than that of H. nudus. Consequently, the invasion of P. crassipes reduced the width of L. sitkana‘s spatial refuge from predation. The permanent presence of this subtropical predator could reduce the intertidal distribution of this temperate gastropod, thereby causing contraction of its southern range limit.
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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 | 0.000 |
| 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 | 0.000 |
| 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".