THE EFFECTS OF PREDATION ON THE PRESERVATION OF ONTOGENETICALLY YOUNG INDIVIDUALS
Bibliographic record
Abstract
Abstract Size-frequency distributions are an integral part of understanding species interactions and population dynamics. Numerous studies have observed that the mode of the size-frequency distribution of fossil assemblages is shifted towards the larger size classes, relative to the mode of live assemblages, suggesting there is a loss of individuals from the smaller size fractions in fossil assemblages. The loss of these individuals is often attributed to size-selective taphonomy, however, selective predation on younger, smaller individuals may also play a role. This study analyzes the effect of predation on the preservation of ontogenetically young individuals by examining predation traces relative to size of biconvex and concavo-convex brachiopods from the Ordovician, Devonian, and Pennsylvanian. We constructed sets of two size-frequency distributions: one based on the size of the brachiopod preserved in the fossil record, and another based on the size of the brachiopod when it was attacked, as indicated by repair scars. For the concavo-convex brachiopods, the size-at-attack and fossil death assemblage curves are different; repairs occurred early in ontogeny, at sizes at which fossils were not preserved. Thus, predation on concavo-convex brachiopods focused on small individuals, the same size that is missing from the fossil record. Furthermore, as the repair frequencies of concavo-convex brachiopods increase, so does the difference between the medians of the distributions, i.e., as repair frequency increases, the fewer ontogenetically young individuals are preserved (Spearman's rank correlation [r = + 0.892, p = 0.012, n = 7]). If size-selective taphonomy had been solely responsible for the loss of ontogenetically young individuals, then there should have been a preferential loss of all small bodied individuals, regardless of taxon or age, but this pattern was not observed. The results presented herein suggest that predation plays a larger role on the preservation of ontogenetically young individuals than has been previously thought.
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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 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".