Spatial and Temporal Variation in the Population Dynamics of the Intertidal Amphipod Corophium Volutator in the Upper Bay of Fundy, Canada
Bibliographic record
Abstract
The scale of variation in population densities and other demographic variables is an important consideration in the design and interpretation of experiments and sampling programs. Here, we studied spatial and temporal variation in populations of Corophium volutator, an intertidal amphipod that is the most abundant macro-invertebrate on mudflats in the upper Bay of Fundy, Canada. Variables that were quantified included density (peaked in mid-summer at |$10,000{\text{s per m}}^2$|), proportion juvenile (an index of population structure), sex ratio (female-biased throughout the year), proportion of females that were ovigerous (reproduction occurs between May and August), and fecundity (number of embryos per female). We studied populations at 4 different sites, i.e., separate mudflats, for 1–2 years, and estimated variance components at 3 spatial scales: metres (samples), 100s of metres (transects) and many kilometres (mudflats). Population density exhibited low variation between years (|$\lt 10\%$| of the random variation), but showed high variation at our smallest and largest spatial scales (45% between samples, 2% between transects, and 40% between mudflats), i.e., the distribution of C. volutator within a mudflat was aggregated at the scale of metres, but not at that of |$100{\rm{s}}$| of metres. Thus, relatively few transects, but many samples per transect, are required for good representation of density on a mudflat. Fecundity was similar between mudflats, but proportion juvenile, sex ratio, and proportion of ovigerous females were strongly affected by site or the interaction between month and site (|$> 60\%$| of the random variation in each case). The high variation observed between mudflats for most demographic variables demonstrates that several control sites are necessary for measuring natural variation, a critical consideration in studies of environmental impacts.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".