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The International Union for Conservation of Nature (IUCN) Red List identifies threatened and endangered species and is a key instrument in global biodiversity conservation efforts. Our understanding of the structure and value of genetic biodiversity below the species level is rapidly increasing. Nonetheless, the IUCN assessment criteria overlook genetic variation within species. Here, we address this blind spot and discuss the principles of species conservation status classification relative to intraspecific biodiversity. We focus on coastal species, which thrive in heterogeneous environments known to drive genetic differentiation. The focal example species, Atlantic cod and sugar kelp, have contrasting life histories, are ecologically and economically important constituents of the coastal ecosystem, and are currently not classified as threatened in Norway and Canada. We expose important variation in population structure, the presence of ecotypes and genetic-environment covariation, as well as loss of ecotypes that threatens the conservation of these species. Because the genetic makeup of species directly influences their resilience, omitting this information from conservation status assessments can result in loss of adaptive capacity to future stressors, such as climate change. Consequently, recognizing and preserving intraspecific variation emerges as vital for species' abilities to adapt to and survive in future ocean conditions. [ABSTRACT FROM AUTHOR]

We employed common-garden experiments to test for genetic variation in responses of larval life-history traits to temperature between two populations of Atlantic cod (Gadus morhua L., 1758) that naturally experience contrasting thermal environments during early life due to spatial and temporal differences in spawning. Southern Gulf of St. Lawrence cod larvae experienced faster growth in warmer water and low, uniform survival across all experimental temperatures (3, 7, 11 °C), consistent with previous studies on this spring-spawning population. In contrast, larvae from fall-spawning Southwestern Scotian Shelf cod collected near Sambro, Nova Scotia, lacked plasticity for growth but experienced much lower survival at higher temperatures. Phenotypes that are positively associated with fitness were observed at temperatures closest to those experienced in the wild, consistent with the hypothesis that these populations are adapted to local thermal regimes. The lack of growth plasticity observed in Sambro cod might be due to costly maintenance of plasticity in stable environments or energy savings at cold temperatures. However, additional experiments need to be conducted on Sambro cod and other fall-spawning marine fishes to determine to what extent responses to projected changes in climate will differ among populations. Key words: Atlantic cod, climate change, early life-history traits, Gadus morhua, local adaptation, marine fish larvae, phenotypic plasticity, thermal reaction norm. Nous avons utilise des experiences de jardin commun pour examiner la variation genetique des reactions de caracteres du cycle biologique larvaire a la temperature entre deux populations de morues (Gadus morhua L., 1758) caracterisees par differents milieux thermiques naturels au debut de leurs cycles biologiques respectifs, dus a des variations spatiales et temporelles du frai. Des larves de morue de la partie meridionale du golfe du Saint-Laurent sont caracterisees par une croissance plus rapide en eau plus chaude et un taux de survie faible et uniforme pour toutes les temperatures experimentales (3,7,11 °C), ce qui concorde avec les resultats d'etudes anterieures sur cette population a frai printanier. En comparaison, des larves de morue de la partie sud-ouest de la plate-forme Neo-Ecossaise, une population a frai automnal, prelevees pres de Sambro (Nouvelle-Ecosse), ne presentaient pas une plasticite de la croissance, mais etaient caracterisees par des taux de survie beaucoup plus bas aux temperatures plus elevees. Les phenotypes positivement associes a l'aptitude ont ete observes aux temperatures s'approchant le plus de celles du milieu naturel, ce qui concorde avec l'hypothese que ces populations sont adaptees a leurs regimes thermiques locaux. L'absence de plasticite de la croissance observee chez les morues de Sambro pourrait etre due au cout eleve du maintien de la plasticite dans des milieux stables ou a des economies d'energie a basse temperature. D'autres experiences doivent toutefois etre realisees sur les morues de Sambro et d'autres poissons a frai automnal afin de determiner l'ampleur des variations futures entre populations des reactions aux changements climatiques anticipes. [Traduit par la Redaction] Mots-cles : morue, changement climatique, caracteres du debut du cycle biologique, Gadus morhua, adaptation locale, larves de poisson marin, plasticite phenotypique, norme de reaction thermique., Introduction Knowledge of the capacity of a species or population for phenotypic change, and how this capacity evolves, is fundamentally important for predicting how an organism will be affected by [...]

The ability of populations to adapt to environmental change and the spatial scale at which this adaptation occurs are fundamentally important issues in evolutionary biology, and ones that may benefit greatly from the study of genetic variability in reaction norms, which represent the plasticity of phenotypic traits across an environmental gradient. Therefore variable reaction norms can reflect genetic differences in the ability of individuals, families, populations, and species to respond to natural and anthropogenic environmental change. Fishes are ideal organisms in which to study plasticity because of their remarkable intraspecific morphological, physiological, behavioural, and life history variation. Here, we review studies demonstrating genetic variability in reaction norms in fishes. Genetic variability in plasticity among full- and half-sib families suggests potential for some populations to develop an adaptive norm of reaction (recalling that plasticity need not be adaptive). Reaction norm variability among populations suggests that adaptive genetic divergence can occur rapidly when selection pressures are strong and that the spatial scale of adaptation is much smaller than previously believed for some species with high dispersal capabilities. These studies demonstrate the potential of using reaction norms to study the evolution of novel phenotypes and the influence of temporal environmental variability and gene flow on the evolution of phenotypic plasticity, which can then be used to predict how populations will respond to directional environmental change. To promote future research into genetic variability in reaction norms, we propose questions that would benefit from such an approach and discuss some important considerations for designing experiments to investigate questions related to genetic variation in plasticity and phenotypic evolution. Key words: phenotypic plasticity, genotype-environment interaction, adaptation, environmental change. La capacite d'adaptation au changement environnemental et l'echelle spatiale a laquelle cette adaptation survient, constituent des defis d'importance fondamentale en biologie evolutive, un sujet qui pourrait beneficier grandement de l'etude de la variabilite des normes de reaction. Les normes de reaction representent la plasticite des traits phenotypiques le long d'un gradient environnemental. Consequemment, des normes de reaction variables peuvent refleter des differences genetiques dans la capacite des individus, des familles, des populations et des especes a reagir au changement environnemental naturel et anthropogene. Les poissons constituent des organismes ideaux pour l'etude de la plasticite compte tenu de la variation intraspecifique remarquable de leur morphologie, de leur physiologie, de leur comportement et de leur cycle de vie. Les auteurs passent en revue les etudes demontrant la variabilite genetique des normes de reaction chez les poissons. La variabilite de la plasticite parmi les familles biparentales ou mono parentales suggere la capacite de certaines populations a developper une norme de reaction adaptative (en se rappelant que la plasticite ne doit pas necessairement etre adaptative). La variabilite des normes de reaction parmi les populations suggere qu'une divergence genetique adaptative peut se manifester rapidement, lorsque les pressions de selection sont fortes et que l'echelle spatiale d'adaptation est beaucoup plus petite qu'on le croyait, chez certaines especes ayant de fortes capacites de dispersion. Ces etudes demontrent que le potentiel de l'utilisation des normes de reaction pour etudier l'evolution de nouveaux phenotypes et l'influence de la variabilite temporelle environnementale ainsi que flux de genes sur l'evolution de la plasticite phenotypique, lesquels peuvent alors etre utilises pour predire comment les populations repondront au changement environnemental directionnel. Pour promouvoir des recherches futures sur la variabilite genetique des normes de reaction, les auteurs proposent quelques questions qui beneficieraient d'une telle approche, et discutent quelques considerations importantes pour concevoir des experiences soulevant des questions reliees a la variation genetique de la plasticite de l'evolution phenotypique. [Traduit par la Redaction] Mots-cles: plasticite phenotypique, interaction genotype environnement, adaptation, changement environnemental., Introduction The ability of individuals or populations to respond to environmental change is integral to species persistence. If a fitness-related trait is optimally expressed in specific environmental conditions, then a [...]

The protracted spawning period of broadcast-spawning marine fishes has potential to generate considerable variability in metrics of individual reproductive output. We undertook a temporally detailed genetic study of larvae produced by Atlantic cod (Gadus morhua) from two spatially proximate populations spawning under controlled semi-natural conditions over 94 days. Based on daily samples of larvae (n = 4489 in total), we document fine-scaled temporal changes in, and correlates of, offspring phenotype and reproductive output (egg batches produced or fertilized). Larval length and standardized yolk-sac volume declined 11 and 49% over the spawning period, respectively. The adaptive significance of these trends is unclear. Longer, heavier females produced longer, better-provisioned larvae. Body size affected the number of egg batches to which an individual contributed genetically but not spawning duration. Males contributed gametes to a greater number of egg batches (19.5 vs. 9.2), and spawned over a longer period of time (48.9 vs. 30.8 days), than females. After accounting for body size and condition, egg batch number and spawning duration differed between adjacent populations separated by < 10 km. Our work highlights the need to understand the environmental and adaptive causes of temporal variability in offspring quality and its consequences to individual fitness and per capita population growth in batch-spawning fishes. [ABSTRACT FROM AUTHOR]

Characterization and population genetic analysis of multilocus genes, such as those found in the major histocompatibility complex ( MHC) is challenging in nonmodel vertebrates. The traditional method of extensive cloning and Sanger sequencing is costly and time-intensive and indirect methods of assessment often underestimate total variation. Here, we explored the suitability of 454 pyrosequencing for characterizing multilocus genes for use in population genetic studies. We compared two sample tagging protocols and two bioinformatic procedures for 454 sequencing through characterization of a 185-bp fragment of MHC DRB exon 2 in wolverines ( Gulo gulo) and further compared the results with those from cloning and Sanger sequencing. We found 10 putative DRB alleles in the 88 individuals screened with between two and four alleles per individual, suggesting amplification of a duplicated DRB gene. In addition to the putative alleles, all individuals possessed an easily identifiable pseudogene. In our system, sequence variants with a frequency below 6% in an individual sample were usually artefacts. However, we found that sample preparation and data processing procedures can greatly affect variant frequencies in addition to the complexity of the multilocus system. Therefore, we recommend determining a per-amplicon-variant frequency threshold for each unique system. The extremely deep coverage obtained in our study (approximately 5000×) coupled with the semi-quantitative nature of pyrosequencing enabled us to assign all putative alleles to the two DRB loci, which is generally not possible using traditional methods. Our method of obtaining locus-specific MHC genotypes will enhance population genetic analyses and studies on disease susceptibility in nonmodel wildlife species. [ABSTRACT FROM AUTHOR]