Northward expansion of the thermal limit for the tick Ixodes ricinus over the past 40 years
Bibliographic record
Abstract
The tick Ixodes ricinus is the main pathogen vector in Europe. Many speculations have been made about the effect of past climate change on the potential distribution of this ectothermic organism, despite a poor understanding of how climate change has resulted in distribution changes to date. In this study, we used a public cross-sectional dataset of I. ricinus abundance at the northern edge of its European distribution for 2016-2017 to identify a thermal limit for I. ricinus distributions. We first modelled the nymphal tick abundance as a function of cumulative annual degree days (DD) > 0°C and biogeographical regions using observations for 2016-2017. We then identified the thermal limit for each biogeographical region as the minimum DD value where the predicted nymph abundance is greater than zero. Hindcasting the identified thermal limit suggested that I. ricinus has expanded its range by approximately 400 km in the Boreal biogeographical region between 1979 and 2020. Despite the lack of long-term data series on tick presence, this finding helps explain numerous observations of I. ricinus in areas presumed to be newly colonised. While multiple other factors affect tick distribution and abundance at the local scale (e.g., host distribution, microhabitat), our approach appears promising for understanding species distribution changes driven by recent climate change. Accounting for biogeographic regions helped consider other dimensions of habitat at a broad scale. Our results underline the relevance of long-term time series data and the risk associated with short-time series for observing changes in 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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| 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".