Langtímabreytileiki í erfðasamsetningu þorsks (Gadus morhua L.) við Ísland
Bibliographic record
Abstract
The population genetics, such as population structure, of Atlantic cod have been unravelled in the last two decades, at an ever finer scale. Yet, much is still unknown about the evolutionary genetics of cod and the possible impact of fisheries on the genetic structure, both temporal and spatial. The objectives of this thesis were to investigate the extent of temporal genetic differentiation in Icelandic cod over the latter half of last century and to correlate historical changes of genetic variation with known factors such as the potential impact of fisheries. \nA prerequisite for such a study is access to historical genetic material and development of the appropriate genetic markers. DNA was obtained from dried tissue on stored cod otoliths, previously used for age determination. These were retrieved from the archives of the Icelandic Marine Research Institute. In the first part of the thesis, specific set of microsatellites markers were developed, suitable for the degraded cod DNA, usually obtained from dried tissue remains. \nSecondly the connection between important behavioral phenotypes and genotypes at non-neutral marker Pan I was determined, using current-day genetic material. This analysis showed that the Pan IAA homozygotes could be assigned to a “coastal” type that appeared to follow seasonal trend in temperature, foraging in relatively shallow waters. On the other hand, most Pan IBB homozygotes were assigned to “frontal” type that is characterized by migrating to colder and deeper waters during feeding migration. \nFor the main part of the thesis historical data set of archived otoliths collected between 1948 and 2002 was used to jointly examine phenotypic and genetic data with the goal to examine historical trends in the genetic composition of the Icelandic cod stock. This analysis showed that there have been major changes in the genetic variation at the Pan I locus of Icelandic cod during the latter part of last century. These have occurred alongside changes in fishing patterns and pressure, and age composition of the stock, whereas no temporal changes were detected in neutral markers. The frequency of the Pan IBB genotype decreased over a period of six decades, concomitant with considerable spatial and technical changes in fishing effort that resulted in the disappearance of older individuals from the fishable stock. \nAnalysis of the neutral historical genetic variation revealed considerable genetic variability. The genetic effective population size (Ne) of cod was estimated to be within the range of few hundreds to several thousand individuals i.e. several magnitudes smaller than the census size. The temporal variation in effective population size of Atlantic cod in Icelandic waters was considerable, likely determined by highly dynamic forces shaping the genetic variation of the population. Indications of subtle changes in genetic differentiation and in Ne highlight the importance of repetitive temporal sampling for detection of any underlying trends which are difficult to detect by other means.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".