Langtímabreytileiki í erfðasamsetningu þorsks (Gadus morhua L.) við Ísland
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Notice bibliographique
Résumé
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.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,052 | 0,008 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découle