Notice bibliographique
Résumé
Intensive field observations were conducted on a small British Columbia coastal stream for two years, supplemented by laboratory rearing and experiment. Stress was placed upon possible isolating mechanisms, as outlined by Mayr, that might serve to keep the marine stickleback (trachurus) and the freshwater form (leiurus)distinct. Lelurus permanently occupies the upper reaches of the stream; trachurus is anadromous, but enters the lower reaches to breed in "pure" freshwater. Between the breeding ground of the two, where some coexistence occurs, hybridization between leiurus and trachurus is extensive, but it is restricted to very narrow zones both in Little Campbell River near Vancouver and in certain Vancouver Island streams. Morphological analysis provides firm circumstantial evidence that hybrids are plentiful and that back-crossing occurs. Hybridization is confirmed by rearing experiments in the laboratory with crosses in all combinations. Most backcrossing is to the freshwater race and this is considered in detail. Behavioural experiments demonstrated the absence of mate preference; random mating occurs with respect to ethological isolation and hybrids perform courtship and parental care activities normally. Rearing hybrids uniformly and in all conbinations demonstrated the absence of genetic incompatibility, and vigorous offspring were produced. Fertile hybrids are abundant in the wild, but the sexes are seasonally isolated from one another. Behavoiral and genetic blocks to hybridization are absent, and thus there is no means to prevent hybridization where leiurus and trachurus come together. But evidence from the field and from preference tests demonstrated that ecological isolating mechanisms are very powerful barriers to hybridization. This is enforced to some extent by partial seasonal isolation, but early spawning migrants make a major contribution to hybridization in the Little Campbell River. Several factors probably operate to cause very narrow hybrid zones in stickle-backs, including a sedentary habit, habitat preference, and hybrid inferiority outside the hybrid zone. The latter could not be detected inside the hybrid zone. The complex of Isolating mechanisms found may well produce stable hybrid zones over long periods of time, and is discussed. Reinforcement of ecological isolating mechanisms probably occurs, and Moore's criticism of the spread of reinforced genotypes would not apply in this instance. Adaptation and consequent ecological isolating mechanisms are the cause of hybrid inferiority. In this instance pre and postmating mechanisms cannot be separated, for they go hand in hand. Geographic speciation is possible but problematical, and sympatric speciation cannot be excluded as a plausible explanation of divergence between sticklebacks as a result of disruptive selection. Distributional patterns of leiurus can best be explained by repeated and independent origins from trachurus. The two forms fulfill the species definition by Mayr and remain reproductively isolated, have well developed isolating mechanisms, and show considerable genetic divergence, much of it polygenic. There is no evidence that, introgression occurs, but a reverse cline in leiurus as well as very narrow hybrid zones demonstrates that selection severely restricts gene flow. Reproductive isolation between marine and freshwater forms seems to be widespread around the hemisphere.
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.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,002 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
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 découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».