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To what degree are patterns of genetic structure in fragmented systems the result of contemporary landscape versus history? We examined the distribution of genetic diversity as a function of colonization history and contemporary landscape in four fish species inhabiting a hierarchically fragmented, unaltered system, the Kogaluk drainage (Labrador): lake trout (Salvelinus namaycush), longnose sucker (Catostomus catostomus), round whitefish (Prosopium cylindraceum), and lake chub (Couesius plumbeus). The footprint of colonization history was still observable in the three species where this issue was examined regardless of the generations since their arrival. Approximate Bayesian computation (ABC) analyses suggest colonization took place from the southwest. The species exhibit similar diversity patterns despite different [[??].sub.e] values and generation intervals. Contemporary gene flow was largely negligible except for gene flow from a centrally located lake. These results suggest landscape has driven colonization history, which still has influence on genetic structuring. The species are widespread. Understanding how they behave in the pristine Kogaluk provides a baseline against which to evaluate how other anthropogenically perturbed systems are performing. Improved understanding of historical and contemporary processes is required to fully explain diversity patterns in complex metapopulations. Dans quelle mesure les motifs de structure genetique dans les systemes fragmentes sont-ils le resultat du paysage actuel plutot que de revolution passee? Nous avons examine la repartition de la diversite genetique en fonction de l'historique de colonisation et du paysage actuel pour quatre especes de poissons occupant un systeme non altere caracterise par une fragmentation hierarchique, le bassin versant de Kogaluk (Labrador), soit le touladi (Salvelinus namaycush), le meunier rouge (Catostomus catostomus), le menomini rond (Prosopium cylindraceum) et le mene de lac (Couesius plumbeus). L'empreinte de l'historique de colonisation est toujours perceptible chez les especes pour lesquelles cet aspect a ete examine, peu importe le nombre de generations depuis leur arrivee. Des analyses ABC (<>) semblent indiquer que la colonisation s'est effectuee a partir du sud-ouest. Les especes presentent des motifs de diversite semblables malgre des valeurs des [[??].sub.e] et intervalles entre generations differents. Le flux genetique actuel est generalement negligeable, sauf en ce qui concerne le flux genetique a partir d'un lac a situation centrale. Ces resultats donnent a penser que le paysage a module l'historique de colonisation, qui exerce toujours une influence sur la structuration genetique. Les especes sont ubiquistes. La comprehension de leur comportement dans le bassin versant intact de Kogaluk fournit une reference par rapport a laquelle evaluer la performance de systemes perturbes par l'activite humaine. Une meilleure comprehension des processus passes et actuels est necessaire pour expliquer en detail les motifs de diversite dans les metapopulations complexes., Introduction To what degree are patterns of observed genetic diversity in complex metapopulation systems the result of contemporary versus historical processes? This is a fundamental question in current conservation and [...]

Marine protected areas (MPAs) can serve as effective tools for the management and conservation of exploited marine species. The Gilbert Bay MPA in coastal Labrador was created to protect a genetically distinct population of Atlantic cod (Gadus morhua); however, decreases in abundance continue to occur potentially due to exploitation outside the MPA. We developed a single-nucleotide polymorphism (SNP) panel to identify Gilbert Bay cod in areas outside MPA boundaries where mixing with offshore cod occurs. In total, 361 individuals from Gilbert Bay, surrounding areas, and offshore were genotyped for 10 913 SNPs. Using [F.sub.ST] rankings and guided regularized random forest, we selected 23 SNPs that together generate 100% accuracy in individual assignment and accurately estimate the proportion of Gilbert Bay cod in fishery samples from sites outside MPA boundaries: on average, fishery samples included 17.3% Gilbert Bay cod. Estimates of effective population size for the Gilbert Bay population ranged from 655 to 1114. Our findings demonstrate the power of using genomic approaches for management of an exploited marine species and enhancing the design of MPAs. Les aires marines protegees (AMP) peuvent etre des outils efficaces pour la gestion et la conservation des especes marines exploitees. L'AMP de Gilbert Bay, le long des cotes du Labrador, a ete creee pour proteger une population genetiquement distincte de morues de l'Atlantique (Gadus morhua); cependant, des baisses d'abondance ont toujours lieu, possiblement en raison de l'exploitation en dehors de l'AMP. Nous avons developpe une puce pour la detection de polymorphismes mononucleotidiques (puce SNP) pour identifier les morues de Gilbert Bay dans des zones situees a l'exterieur des limites de l'AMP, ou ces morues se melangent a des morues d'origine extracotiere. Au total, 361 individus de Gilbert Bay, de zones environnantes et d'origine extracotiere ont ete genotypes pour 10 913 SNP. En utilisant les indices de differentiation ([F.sub.ST]) et une approche de forets aleatoires regularisee guidee, nous avons selectionne 23 SNP qui, collectivement, produisent des affectations individuelles a 100% exactes et estiment avec exactitude la proportion de morues de Gilbert Bay dans les echantillons de poissons provenant de sites a l'exterieur de l'AMP; en moyenne, les morues de Gilbert Bay constituaient 17,3% des echantillons. Les estimations de la taille effective de la population de Gilbert Bay allaient de 655 a 1 114 morues. Nos resultats demontrent la puissance des approches genomiques pour la gestion d'une espece marine exploitee et Amelioration de la conception d'AMP. [Traduit par la Redaction], Introduction Marine protected areas (MPAs) and marine reserves represent valuable tools for conservation and resource management (Gaines et al. 2010) and can play an important role in protecting marine species [...]

Anadromous, resident, and landlocked Arctic char (Salvelinus alpinus) differentially experience drift and gene flow, making them ideal for studying incipient divergence. We investigated genetic divergence within and among char occupying landlocked and sea-accessible sites in Labrador, Canada, using 11 microsatellites. Unlike anadromous char, landlocked char were highly genetically differentiated. Genetic subgroups were detected within landlocked and sea-accessible sites. Within Ramah Lake (a sea-accessible site containing two subgroups), one subgroup matured at a small size, and both subgroups had equal proportions of males to females. These findings refute residency as a sneaker male tactic and instead suggest the presence of reproductively isolated resident and anadromous char. Subgroups demonstrated equal frequencies of Atlantic and Arctic lineage mtDNA haplotypes, suggesting their genetic differences were not due to allopatry during the last glacial maximum. Our results are therefore consistent with the sympatric genetic divergence of resident and anadromous Arctic char morphs. Les ombles chevaliers (Salvelinus alpinus) anadromes, residents et dulcicoles different sur le plan de la derive et du flux genetique, ce qui en fait des candidats ideaux pour etudier les stades initiaux de la divergence. Nous avons etudie la divergence genetique chez les ombles dans certains sites isoles de la mer et d'autres relies a la mer au Labrador (Canada), ainsi qu'entre ces sites, en utilisant 11 microsatellites. Contrairement aux ombles anadromes, les ombles dulcicoles presentaient une forte differenciation genetique. Des sous-groupes genetiques ont ete detectes dans les sites isoles de la mer et relies a la mer. Dans le lac Ramah (un site relie a la mer contenant deux sous-groupes), un des sous-groupes atteignait la maturite a petite taille et les deux sous-groupes presentaient des proportions egales de males et de femelles. Ces constatations demontrent que la residence n'est pas une tactique de males furtifs et indiqueraient plutot la presence d'ombles residents et anadromes isoles sur le plan de la reproduction. Les sous-groupes presentaient des frequences egales d'haplotypes d'ADNmt de filiation atlantique et arctique, ce qui porte a croire que leurs differences genetiques ne sont pas dues a une allopatrie durant le dernier maximum glaciaire. Nos resultats concordent donc avec une divergence genetique sympatrique des morphes d'ombles chevaliers residents et anadromes. [Traduit par la Redaction], Introduction Species that demonstrate phenotypically distinct 'morphs' with a genetic component allow for the study of the factors driving incipient genetic divergence (Schluter 1996, 2001). Probably no species demonstrates this [...]

Polymorphic species are useful models for investigating the evolutionary processes driving diversification. Such processes include colonization history as well as contemporary selection, gene flow, and genetic drift, which can vary between intraspecific morphs as a function of their distinct life histories. The interactive and relative influence of such evolutionary processes on morph differentiation critically informs morph‐specific management decisions and our understanding of incipient speciation. We therefore investigated how geographic distance, environmental conditions, and colonization history interacted with morph migratory capacity in the highly polymorphic fish species, Arctic Charr (Salvelinus alpinus). Using an 87 k SNP chip we genetically characterized recently evolved anadromous, resident, and landlocked charr collected from 45 locations across a secondary contact zone of three charr glacial lineages in eastern Canada. A strong pattern of isolation by distance across all populations suggested geographic distance principally shaped genetic structure. Landlocked populations had lower genetic diversities and higher genetic differentiation than anadromous populations. However, effective population size was generally temporally stable in landlocked populations in comparison to anadromous populations. Genetic diversity positively correlated with latitude, potentially indicating southern anadromous populations' vulnerability to climate change and greater introgression between the Arctic and Atlantic glacial lineages in northern Labrador. Local adaptation was suggested by the observation of several environmental variables strongly associating with functionally relevant outlier genes including a region on chromosome AC21 potentially associated with anadromy. Our results demonstrate that gene flow, colonization history, and local adaptation uniquely interact to influence the genetic variation and evolutionary trajectory of populations. [ABSTRACT FROM AUTHOR]

Assessment of population structure is critical to the design and implementation of sound management and conservation strategies. However, population structure must be assessed using markers attuned to population genetic processes such as genetic drift and gene flow, which reflect actual levels of reproductive isolation among putative genetic clusters. This is critical for highly exploited, commercial species that form the backbone of regional and local economies. Here, we show extremely low levels of population genetic differentiation among Greenland halibut (Reinhardtius hippoglossoides) collected from throughout the Northwest Atlantic, which cannot be statistically differentiated from panmixia using 12 species-specific polymorphic microsatellite markers. In contrast, some previous studies have demonstrated significant differences among individuals collected from various parts of the species' range using a variety of both genetic and nongenetic techniques. In accordance with other reports and consistent with the species' life history, we demonstrate that the most parsimonious explanation reconciling observed patterns is a repeated high degree of local differentiation of new recruits and colonizers originating from a common gene pool. Such a scenario has important conservation implications in terms of devising more appropriate strategies balancing species persistence and replenishment with sustainable resource use. L'revaluation de la structure des populations est essentielle a la conception et la mise en ceuvre de bonnes strategies de gestion et de conservation. La structure des populations doit cependant etre evaluee a l'aide de marqueurs refletant les processus de genetique des populations comme la derive genetique et le flux genetique, qui temoignent de l'ampleur reelle de l'isolement reproductif de differents groupements genetiques presumes. Il s'agit d'une consideration essentielle en ce qui concerne les especes commerciales exploitees intensivement et sur lesquelles reposent des economies regionales et locales. Nous constatons des degres extremement faibles de differenciation genetique de la population pour des fletans du Groenland (Reinhardtius hippoglossoides) captures a la grandeur de l'Atlantique nord-ouest, qui ne peuvent etre distingues statistiquement de la panmixie sur la base de 12 marqueurs microsatellites polymorphiques distincts. Certaines etudes anterieures avaient neanmoins demontre, par des approches genetiques et non genetiques, la presence de differences significatives entre individus captures dans divers secteurs de l'aire de repartition de l'espece. A l'instar d'autres auteurs, nous demontrons que l'explication la plus parcimonieuse des differents motifs observes, qui concorde egalement avec le cycle de vie de l'espece, est un degre eleve repete de differenciation locale de nouvelles recrues et de colonisateurs issus du meme fonds genetique. Ce scenario a d'importantes consequences pour la conservation, notamment en ce qui concerne l'elaboration de strategies permettant un equilibre entre la persistance et la reconstitution d'une part, et l'utilisation durable de la ressource d'autre part. [Traduit par la Redaction], Introduction Preventing biodiversity loss is a key priority for most conservation strategies, yet these are often conceived without proper identification of populations and an understanding of the mechanisms underlying their [...]