No abstract

The effects of introgression on parasitism in brook charr Salvelinus fontinalis were investigated in 28 lakes with various levels of stocking in Québec, Canada. No effect of genetic background on parasitism was found at the individual level. Body length seemed to explain most of the variation observed at this level, with largest fish being more infected. However, lakes with the greater average domestic genetic background were found to display significantly lower parasite prevalence and diversity. Since our results indicate no effect of domestic genes at the individual level, the negative association with introgression found at the population level may be mainly attributed to differences in intrinsic environmental quality of lakes (e.g. fishing pressure, availability of food resources, abiotic characteristics).

Phenotypic changes due to human activities are occurring at a far greater speed than those originating from natural causes in animal populations. For instance, phenotypic divergence among individuals may arise in populations supplemented with farm‐reared fish that are known to display different phenotypes from those of wild individuals because of domestication. Little is known about how these phenotypic differences are maintained when domestic and wild individuals face the same environment and hybridize, as it is the case after supplementation. In this study, we assessed the effect of genetic origin of individuals on phenotypic trait divergence (morphology, growth, and size‐at‐age) in stocked populations of Brook Trout (Salvelinus fontinalis). We also evaluated whether genetic origin influences habitat use by documenting trophic niche and/or level using stable isotope analyses. We found significant effects of genetic origin on phenotypic variables with domestic fish generally being more fusiform and larger than wild and hybrid individuals. Lake identity also explained most of the variation in phenotypic variables, meaning that population‐specific attributes were important drivers of morphology and size. Our results also showed that domestic fish were feeding in more littoral niches and at a higher trophic level than wild and hybrid individuals, suggesting that differences in feeding habits could partially explain phenotypic differences. These results highlight the importance of accounting for the genetic composition of populations when assessing the causes of phenotypic divergence in the wild.

The evolution of reproductive strategies is affected by the ability of organisms to deal with future environmental conditions. When environments are temporally unpredictable, however, it is difficult to anticipate optimal offspring phenotype. Diversification of offspring phenotypes, a strategy called diversified bet‐hedging, may allow parents to maximize their fitness by reducing between‐year variation in reproductive success. The link between diversification of offspring phenotypes and individual reproductive success, however, has rarely been documented empirically. We used an eight‐year dataset (1215 broods, 870 females) on individually marked tree swallows (Tachycineta bicolor) to assess whether intra‐brood mass variation was compatible with a diversified bet‐hedging strategy. Intra‐brood mass variation was weakly, but significantly repeatable within females, suggesting consistent individual differences. Greater intra‐brood mass variation, however, was not associated with reduced between‐year variation in reproductive success or increased female reproductive success. Moreover, contrary to diversified bet‐hedging expectations, fledging success of large broods was greater when hatchlings had similar rather than variable masses. Our results suggest that intra‐brood mass variation may not result from diversified bet‐hedging, but rather from complex interactions between environmental, brood, and maternal characteristics.

Higher temperatures are now observed in several ecosystems and act as new selective agents that shape traits and fitness of individuals. Transgenerational effects may be important in modulating adaptation of future generations and buffering negative impacts of temperature changes. The potential for these effects may be important in