Quantitative genetic variation of development rate was evident among 20 half-sib and 40 full-sib families within each of two seasonally separate components of a population of pink salmon (Oncorhynchus gorbuscha) (H o : no sire effect on temperature units at hatch, P < 0.02). Differences between averages of families spawned 3 weeks apart may have had genetic or environmental sources (e.g., in constant 8°C, early embryos hatched at 606 temperature units, and late embryos, at 625). Statistical interactions between paternal effects and environment (embryos were cultured in four temperature regimes, two simulated natural regimes and two constant temperatures; H o : no sire by regime interaction effect on temperature units at hatch, P < 0.09) were weak evidence that genotype by environment interactions contributed to variation. Paternal effects in analysis of variance (evidence of additive genetic variation) were detected only at later stages. Evidences of genetic variation and of interactions between genotypes and environments are pertinent to resource conservation because they suggest that harvest management or hatchery practice have the potential to reduce genetic variation in salmon populations.Résumé : Une variation génétique quantitative du taux de développement était apparente chez 20 familles de demifrères et 40 familles de plein-frères au sein de deux composantes saisonnières distinctes d'une population de saumon rose, Oncorhynchus gorbuscha. (H o : aucun effet du père sur le nombre d'unités de température au moment de l'éclosion, P < 0,02). Les écarts notés entre les moyennes des familles dont la fécondation présentait trois semaines d'intervalle peuvent s'expliquer par des facteurs génétiques ou environnementaux (p. ex. : à une température constante de 8°C l'éclosion des embryons se produisait à 606 unités de température pour les plus hâtifs et à 625 pour les plus tardifs). Les interactions statistiques entre les effets paternels et l'environnement (embryons élevés sous quatre régimes de température, deux régimes naturels simulés et deux à température constante; H o : aucune interaction père-régime sur les unités de température à l'éclosion, P < 0,09) constituaient un indice faible du faible apport à la variation des effets de l'environnement sur le génotype. Une analyse de variance des effets paternels (évidence d'une variation génétique additive) n'a permis de mettre ces derniers en évidence qu'aux stades ultérieurs. L'existence de signes de variation génétique et d'interactions entre les génotypes et les environnements s'avère pertinente pour la conservation des ressources car elle indique que la gestion de la récolte ou les pratiques des piscicultures pourraient influer sur la variation génétique des populations de saumon.[Traduit par la Rédaction]
A three year ecological study was made of the Smooth snake in the New Forest, Hampshire. The aim was to provide quantitative information on particular aspects of the Smooth snake's life‐history characteristics. On three study sites, snakes were captured by hand and individually marked. On capture, each snake was identified, sexed, measured, weighed and examined for the presence of food in its stomach and hind gut. In general, mature Smooth snakes showed sexual dimorphism in morphology and growth rates. This was thought to reflect the influence of body size on female reproduction. It was found that Smooth snakes preyed on both small mammals and lizards, suggesting that this species is an opportunist predator. Diet did not vary between study sites. The population sizes were estimated by direct enumeration and densities of one and two snakes per hectare were found. The sex ratios in each study site population were even, and the age structures suggested that both sexes exhibited similar mortality. Consideration was also given to the estimation of the total population size of Smooth snakes in Britain. Summary The morphology, growth, food habits and population characteristics of the Smooth snake Coronella austriaca Laurenti were studied in southern England. On capture, each snake was identified, sexed, measured, weighed and examined for the presence of food in its stomach and hind gut. In total, measurements of 22 sexually immature and 92 sexually mature snakes were collected. There was little evidence for sexual dimorphism among immature snakes, though males had relatively longer tails than females. Among mature snakes, females had longer snout‐vent lengths and shorter tails than males. The body weights of breeding females were heavier than those for both non‐breeding females and males. Regardless of age or sex, body weight was positively correlated with snout‐vent length. An analysis of 68 growth measurements revealed that, in common with other species of snake, immature specimens had higher growth rates than mature specimens. Growth within one year did not differ appreciably between males and females. Conversely, growth over more than one year was greatest for female snakes. These differences in morphology and growth were ascribed to the influence that body size has on reproductive success. Large females (i) produce large offspring, and (ii) may have an increased chance of courtship and mating. During non‐breeding years it is suggested that females offset the cost of reproduction through an allocation of energy reserves to bodily growth. Thus individuals may “choose” to grow rather than to breed in particular years. Hence, females in the resting phase of their reproductive cycles may exhibit high growth rates. The Smooth snakes preyed on lizards and small mammals. Nestling prey (young rodents and young shrews taken from underground nests) were the most important dietary items. It was suggested that the Smooth snake is less specialized in its choice of prey than has been previously reported. It was considered to be a...
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