Testing propagule pressure theory: maritime transport & invasion by fouling species
Bibliographic record
Abstract
Introductions of exotic fouling species have severely disrupted marine ecosystems. Theory suggests that high propagule pressure increases the probability of successful establishment. Likewise, empirical studies have shown the importance of ships and boats for transporting exotic species. However, few empirical studies have demonstrated the effect of propagule pressure on invasion success. For marine fouling species, uncertainty about vectors and pathways further impedes our ability to calculate propagule pressure and to understand establishment success. My goal was to better understand the links between propagule pressure from maritime activities and the spatial distribution of exotic fouling species. Using empirical data, I (1) determined the importance of boat characteristics and propagule exposure on boat fouling, (2) demonstrated the roles of commercial shipping and recreational boating in the invasion process, and (3) tested the effect of propagule pressure on population and community diversity. Although boats on the east coast of Canada were less fouled than New Zealand boats, boat-mediated spread may be facilitated in Canada by greater movement of boats among marinas than in New Zealand. Propagule exposure better predicted boat fouling than did boat characteristics. The spatial genetic structure of the colonial tunicate, Botryllus schlosseri, suggests that ships have frequently introduced it to the east coast of Canada and that secondary spread occurs gradually around individual ports, facilitated by recreational boating. The diversity of invasive species within commercial ports is positively related to propagule pressure and invasion success at both community (i.e. inter-specific richness) and population levels (i.e. genetic diversity). Diversity was significantly correlated to the numbers of ship arrivals but not to ballast water discharge events or the volume of ballast water discharged. This suggests that hull biofouling is a more important pathway than ballast water for exotic fouling species. Both boats and ships have influenced the invasion process of fouling species in Canadian coastal areas. The research also underlines the point that predictive models for the spread of biofouling species should be based on regional boating patterns, boating characteristics, and local propagule exposure. Defining relationships between propagule pressure and invasion success is one of the great challenges to understanding the rapid changes occurring in marine ecosystems.
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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 | 0.016 | 0.095 |
| Meta-epidemiology (narrow) | 0.002 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.003 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.011 | 0.001 |
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".