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While it is likely that ecological context is important, the factors that facilitate and maintain variable levels of intraspecific diversity in Salmonidae fishes across environments remain unclear. Using a meta‐analysis of sympatric ecotype assemblages from two salmonid genera—Salvelinus and Coregonus—we evaluated the importance of ecological factors determining the number of sympatric ecotypes (i.e. 2–7) and the level of trait divergence between them. We found that ecotype diversity increased with lake depth and surface area in both Coregonus and Salvelinus. Further, diversity in Coregonus increased with latitude, while the number of ecotypes in Salvelinus assemblages was linked to climatic seasonality. In comparing the two genera, we found elevated divergence in traits related to ontogeny (i.e. age and body shape) in Salvelinus and gill raker count in Coregonus. Trait divergence in life history traits (i.e. age and body length) in Salvelinus increased with seasonality, whereas contrasting relationships of latitude to body length and gill rakers were found in Coregonus. We also found similar levels of divergence in trait variance in the two genera, suggesting that among‐ecotype differences in phenotypic variability are not more common in one genus than the other. Overall, ecosystem characteristics, including lake location, climate and morphometry, are clearly important for where these genera have diversified, but the variables that are most closely associated with intraspecific diversity differ between the two genera studied and depend on whether diversity is quantified using number of ecotypes or trait divergence. [ABSTRACT FROM AUTHOR]

Conflicts can arise in developmental pathways that prevent an individual entering different developmental life stages that result in the expression of different phenotypes within a specific time period. In salmonids, theory suggests that sexual maturation may inhibit subsequent smolting within the same 12‐month period and that this is partly the result of the time and the apparently conflicting physiological changes for these processes to occur, and partly because of the energy requirements for these physiologically taxing processes. This study tested whether sexually mature male Atlantic salmon (Salmo salar L.) parr, caught in the autumn, would subsequently smolt the following spring. Through individual identification using PIT telemetry, minimum estimates of 3.0% (n = 6/203) and 5.9% (n = 1/17) of Atlantic salmon parr that were sexually mature in two river catchments during the autumn were subsequently identified as smolts in the following spring. We therefore suggest that, in line with previous studies on domesticated Atlantic salmon and laboratory‐based experiments, there is no developmental conflict but that life‐history expression is mediated by environmental and genetic processes. [ABSTRACT FROM AUTHOR]

Patterns in phenotypic and genotypic diversity within many species are becoming increasingly apparent, although there remain many species for which such patterns have yet to be described adequately.Fishes from recently glaciated ecosystems are likely to be particularly rich in intraspecific diversity, yet current conservation management strategies are, in many parts of the world, particularly in Europe, conventionally and overwhelmingly focused on species, regardless of competing species concepts, and appropriate policies for managing diversity at a sub‐specific level still have to be developed.Occasional attempts to protect certain vulnerable ecotypes and proposed alternative units of conservation (e.g. 'Pragmatic Species' or 'Evolutionarily Significant Units') reinforce the conventional primacy of contemporary expressed patterns of variation.Intraspecific phenotypic and genotypic patterns are ultimately the result of complex processes of divergence; conservation approaches that focus on the products of evolution largely ignore the processes that generate and maintain those patterns. Policies that acknowledge the continuation of evolution, the derivation of novel diversity over often very short time spans and the role of environment in initiating and perpetuating these processes are poorly integrated into management strategy.To address possible deficits, where intraspecific diversity is not addressed in management practice, we believe it to be important first to characterize hidden genetic and phenotypic diversity, which may intimate eco‐evolutionary processes, initially among species of high conservation status. A second step should be to use an approach to intraspecific diversity that illuminates the ultimate processes and mechanisms that bring about that diversity, which also concedes the central role of the environment and affords adequate protection to the ecosystems that drive these processes, such as the United Nations Convention on Biological Diversity (CBD) Ecosystems approach. [ABSTRACT FROM AUTHOR]

Partial migration, in which some individuals of a population migrate while other individuals remain resident, is generally associated with ontogenetic shifts to better feeding or as a response to adversity, but its underlying mechanisms remain relatively unknown. Brown trout (Salmo trutta) exhibit partial migration, with some individuals remaining in fresh water (freshwater-resident) while others undertake an anadromous migration, gain most of their adult size at sea, and then return to fresh water to spawn. The option adopted by an individual trout is thought to be partly determined by its growth performance in early life, which in the stochastic and dynamic environment of freshwater streams may be dependent on its flexibility. To examine potential effects of parent type on phenotypic flexibility, we measured the metabolism, growth, and morphology of full-sibling groups of offspring from freshwater-resident and anadromous parents both before and after a switch in diet. We found that fry had a higher growth rate and a more rounded head and body shape when reared on chironomid larvae compared with when they were reared on Daphnia, but diet had no effect on standard metabolic rate. Interestingly, offspring of anadromous parents were less able to maintain their growth rate when fed on Daphnia than were those of freshwater-residents and showed a correspondingly greater increase in growth following a switch from Daphnia to chironomid larvae. Offspring of anadromous parents also showed less morphological flexibility in response to diet than did the offspring of freshwater-residents. We discuss how the migration history of the parents might interact with phenotypic flexibility in early life to influence the migration probability of the offspring. La migration partielle, selon laquelle certains individus d'une population migrent alors que d'autres demeurent residents, est generalement associee a des changements ontogeniques visant une meilleure alimentation ou a une reaction a l'adversite. Les mecanismes de la migration partielle demeurent toutefois meconnus. Les truites de mer (Salmo trutta) font preuve de migration partielle, certains individus demeurant en eau douce (residents d'eau douce), alors que d'autres entreprennent une migration anadrome, la majeure partie de leur croissance jusqu'a la taille adulte s'effectuant en mer avant qu'ils ne retournent en eau douce pour frayer. L'option adoptee par une truite donnee serait en partie determinee par sa performance de croissance au debut de la vie qui, dans le milieu stochastique et dynamique des cours d'eau douce, pourrait dependre de sa flexibilite. Afin d'examiner les effets potentiels du type parental sur la flexibilite phenotypique, nous avons mesure le metabolisme, la croissance et la morphologie de groupes de pleine fratrie de progeniture de parents residents d'eau douce et anadromes, avant et apres un changement de regime alimentaire. Nous avons constate que les alevins se nourrissant de larves de chironomides presentaient un taux de croissance plus grand et avaient des tetes et des corps plus arrondis que ceux se nourrissant de Daphnia, mais le regime alimentaire n'avait pas d'effet sur le metabolisme standard. Fait interessant, la progeniture de parents anadromes etait moins en mesure de maintenir son taux de croissance quand elle se nourrissait de Daphnia que la progeniture de residents d'eau douce, et elle presentait une augmentation consequente de sa croissance quand elle passait d'une alimentation a base de Daphnia a un regime de larves de chironomides. La progeniture de parents anadromes presentait egalement une moins grande flexibilite morphologique en reponse a l'alimentation que la progeniture de residents d'eau douce. Nous abordons l'influence possible de l'interaction de l'historique de migration des parents avec la flexibilite phenotypique au debut de la vie sur la probabilite de migration de la progeniture. [Traduit par la Redaction], Introduction Phenotypic flexibility, an organism's ability to match its morphology and physiology to current environmental conditions, is fundamental to adaptability and occurs when complementary combinations of traits change in response [...]