Changes in taxonomy and species distributions and their influence on estimates of faunal homogenization and differentiation in freshwater fishes
Bibliographic record
Abstract
Abstract Aim To assess how changing taxonomy and distribution data affect estimates of faunal homogenization and differentiation as agents of global change in freshwater fishes. Location Provinces and territories of Canada. Methods Species presence–absence data were collated in 2000 and 2005 from regional and national lists, and faunal homogenization and differentiation were calculated using Jaccard’s faunal similarity index. Differences between time periods and areas were summarized using principal coordinate analysis. Differences in faunal assemblages between native and total faunas were assessed via Whittaker’s (1960) beta diversity (βw) index and tests of differences in multivariate dispersion of fish species compositions. Results Among aquatic ecoregions in one province (British Columbia) there were four taxonomic changes and 18 distributional changes between the 2000 and 2005 databases. Pairwise Jaccard’s faunal similarity index between the eight aquatic ecoregions declined by an average of 4.8% from 35.9% in native faunas to 31.1% in total faunas (introductions – extinctions/extirpations) indicating overall faunal differentiation. Average pairwise similarity declined by 0.9% between 2000 and 2005. Across thirteen provinces and territories of Canada, there were five taxonomic changes and 61 distributional changes between the 2000 and 2005 databases. Generally, faunal homogenization increased; pairwise Jaccard’s increased by an average of 1.8% from 27.1% in native faunas to 28.9% in total faunas or an average of 0.6% per comparison. Main conclusions Despite changing taxonomy and fish distribution information, comparative analysis of 2000 and 2005 databases consistently show overall faunal differentiation at the smallest (provincial) spatial scale and homogenization at the largest scale (across Canada) and that these trends continued between time periods. Homogenization and differentiation followed expectations from conceptual models based on the relative prevalence of species invasions and extinctions within communities. General conclusions of the onset and extent of homogenization and differentiation were relatively insensitive to our changing understanding of taxonomy and distribution.
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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 | 0.002 | 0.010 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| 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".