<scp>CATS</scp> regression – a model‐based approach to studying trait‐based community assembly
Bibliographic record
Abstract
Summary Shipley, Vile & Garnier (Science 2006; 314: 812) proposed a maximum entropy approach to studying how species relative abundance is mediated by their traits, ‘community assembly via trait selection’ (CATS). In this paper, we build on recent equivalences between the maximum entropy formalism and Poisson regression to show that CATS is equivalent to a generalized linear model for abundance, with species traits as predictor variables. Main advantages gained by access to the machinery of generalized linear models can be summarized as advantages in interpretation, model checking, extensions and inference. A more difficult issue, however, is the development of valid methods of inference for single‐site data, as species correlation in abundance is not accounted for in CATS (whether specified as a regression or via maximum entropy). This issue can be circumvented for multisite data using design‐based inference. These points are illustrated by example – our plant abundances were found to violate the implicit Poisson assumption of CATS, but a negative binomial regression had much improved fit, and our model was extended to multisite data in order to directly model the environment–trait interaction. Violations of the Poisson assumption were strong and accounting for them qualitatively changed results, presumably because larger counts had undue influence when overdispersion had not been accounted for. We advise that future CATS analysts routinely check for overdispersion and account for it if present.
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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 | 0.005 | 0.015 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.008 | 0.002 |
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".