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Personne :
Bernatchez, Louis

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Bernatchez

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Louis

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Université Laval. Département de biologie

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ncf10177475

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  • PublicationRestreint
    Integrative use of spatial, genetic, and demographic analyses for investigating genetic connectivity between migratory, montane, and sedentary caribou herds
    (Blackwell scientific, 2007-09-06) Boulet, Marylène; Bernatchez, Louis; Couturier, Serge; Côté, Steeve D.; Otto, Robert D.
    Genetic differentiation is generally assumed to be low in highly mobile species, but this simplistic view may obscure the complex conditions and mechanisms allowing genetic exchanges between specific populations. Here, we combined data from satellite‐tracked migratory caribou (Rangifer tarandus), microsatellite markers, and demographic simulations to investigate gene flow mechanisms between seven caribou herds of eastern Canada. Our study included one montane, two migratory, and four sedentary herds. Satellite‐tracking data indicated possibilities of high gene flow between migratory herds: overlap of their rutting ranges averaged 10% across years and 9.4% of females switched calving sites at least once in their lifetime. Some migratory individuals moved into the range of the sedentary herds, suggesting possibilities of gene flow between these herds. Genetic differentiation between herds was weak but significant (FST = 0.015): migratory and montane herds were not significantly distinct (FST all ≤ 0.005), whereas sedentary herds were more differentiated (FST = 0.018–0.048). Geographical distances among sedentary herds limited gene flow. Historical estimates of gene flow were higher from migratory herds into sedentary herds (4Nm all > 9) than vice‐versa (4Nm all < 5), which suggests migratory herds had a demographic impact on sedentary herds. Demographic simulations showed that an effective immigration rate of 0.0005 was sufficient to obtain the empirical FST of 0.015, while a null immigration rate increased the simulated FST to > 0.6. In conclusion, the weak genetic differentiation between herds cannot be obtained without some genetic exchanges among herds, as demonstrated by genetic and spatial data.
  • PublicationAccès libre
    Temporally dynamic habitat suitability predicts genetic relatedness among caribou
    (The Royal Society Publishing, 2014-08-13) Dussault, Christian; Pellissier, Loïc; Yannic, Glenn; Côté, Steeve D.; Le Corre, Mael René Vincent; Bernatchez, Louis
    Landscape heterogeneity plays a central role in shaping ecological and evolutionary processes. While species utilization of the landscape is usually viewed as constant within a year, the spatial distribution of individuals is likely to vary in time in relation to particular seasonal needs. Understanding temporal variation in landscape use and genetic connectivity has direct conservation implications. Here, we modelled the daily use of the landscape by caribou in Quebec and Labrador, Canada and tested its ability to explain the genetic relatedness among individuals. We assessed habitat selection using locations of collared individuals in migratory herds and static occurrences from sedentary groups. Connectivity models based on habitat use outperformed a baseline isolation-by-distance model in explaining genetic relatedness, suggesting that variations in landscape features such as snow, vegetation productivity and land use modulate connectivity among populations. Connectivity surfaces derived from habitat use were the best predictors of genetic relatedness. The relationship between connectivity surface and genetic relatedness varied in time and peaked during the rutting period. Landscape permeability in the period of mate searching is especially important to allow gene flow among populations. Our study highlights the importance of considering temporal variations in habitat selection for optimizing connectivity across heterogeneous landscape and counter habitat fragmentation.
  • PublicationRestreint
    Integrating ecological and genetic structure to define management units for caribou in Eastern Canada
    (2015-11-26) Bernatchez, Louis; St-Laurent, Martin-Hugues; Yannic, Glenn; Ortego, Joaquin; Côté, Steeve D.; Taillon, Joëlle; Beauchemin, Alexandre; Dussault, Christian
    Genetic diversity is a key parameter to delineate management units, but many organisms also display ecological characteristics that may reflect potential local adaptations. Here, we used ecological and genetic information to delineate management units for a complex system involving several ecotypes of caribou (Rangifer tarandus) from Québec and Labrador, eastern Canada. We genotyped 560 caribou at 16 microsatellite loci and used three Bayesian clustering methods to spatially delineate and characterize genetic structure across the landscape. The different approaches employed did not converge on the same solution, and differed in the number of inferred genetic clusters that best fit the dataset but also in the spatial distribution of genetic variation. We reconciled variability among the methods using a synthetic approach that considers the sum of the partitions obtained by each of them and retrieved six genetically distinct groups that differ in their spatial extent across the range of caribou in the study area. These genetic groups are not consistent with the presently defined ecological designations for this species. Combining both genetic and ecological criteria, we distinguished eight independent management units. Overall, the management units we propose should be the focus of conservation and management actions aimed to maximize genetic and ecological diversity and ensure the persistence of caribou populations inhabiting increasingly disturbed landscapes.