Single nucleotide polymorphisms unravel hierarchical divergence and signatures of selection among Alaskan sockeye salmon (Oncorhynchus nerka) populations

<p>Abstract</p> <p>Background</p> <p>Disentangling the roles of geography and ecology driving population divergence and distinguishing adaptive from neutral evolution at the molecular level have been common goals among evolutionary and conservation biologists. Using single nucleotide polymorphism (SNP) multilocus genotypes for 31 sockeye salmon (<it>Oncorhynchus nerka</it>) populations from the Kvichak River, Alaska, we assessed the relative roles of geography (discrete boundaries or continuous distance) and ecology (spawning habitat and timing) driving genetic divergence in this species at varying spatial scales within the drainage. We also evaluated two outlier detection methods to characterize candidate SNPs responding to environmental selection, emphasizing which mechanism(s) may maintain the genetic variation of outlier loci.</p> <p>Results</p> <p>For the entire drainage, Mantel tests suggested a greater role of geographic distance on population divergence than differences in spawn timing when each variable was correlated with pairwise genetic distances. Clustering and hierarchical analyses of molecular variance indicated that the largest genetic differentiation occurred between populations from distinct lakes or subdrainages. Within one population-rich lake, however, Mantel tests suggested a greater role of spawn timing than geographic distance on population divergence when each variable was correlated with pairwise genetic distances. Variable spawn timing among populations was linked to specific spawning habitats as revealed by principal coordinate analyses. We additionally identified two outlier SNPs located in the major histocompatibility complex (MHC) class II that appeared robust to violations of demographic assumptions from an initial pool of eight candidates for selection.</p> <p>Conclusions</p> <p>First, our results suggest that geography and ecology have influenced genetic divergence between Alaskan sockeye salmon populations in a hierarchical manner depending on the spatial scale. Second, we found consistent evidence for diversifying selection in two loci located in the MHC class II by means of outlier detection methods; yet, alternative scenarios for the evolution of these loci were also evaluated. Both conclusions argue that historical contingency and contemporary adaptation have likely driven differentiation between Kvichak River sockeye salmon populations, as revealed by a suite of SNPs. Our findings highlight the need for conservation of complex population structure, because it provides resilience in the face of environmental change, both natural and anthropogenic.</p

Weight gain since menopause and its associations with weight loss maintenance in obese postmenopausal women

M S&eacute;n&eacute;chal1,2, H Arguin6, DR Bouchard4,5, AC Carpentier3, JL Ardilouze3, IJ Dionne1,2, M Brochu1,21Research Centre on Aging, Health and Social Services Centre, University Institute of Geriatrics of Sherbrooke, 2Faculty of Physical Education and Sports, University of Sherbrooke, 3Clinical Research Centre, Sherbrooke University Hospital Centre, Sherbrooke, QC; 4Faculty of Kinesiology and Recreation Management, University of Manitoba, Winnipeg, MB; 5Health, Leisure &amp; Human Performance Research Institute, Winnipeg, MB; 6Division of Kinesiology, Department of Social and Preventive Medicine, Faculty of Medicine, Laval University, QC, CanadaObjective: To examine the association between weight gain since menopause and weight regain after a weight loss program.Methods: Participants were 19 obese women who participated in a 15-week weight loss program and a 12-month follow-up. Main outcomes were: body composition, resting metabolic rate, energy intake, energy expenditure, and weight regain at follow-up.Results: All body composition measures significantly decreased after intervention (all P &le; 0.01) while all measures of fatness increased significantly after the 12-month follow-up (P &le; 0.01). Body weight gain since menopause was associated with body weight regain (r = 0.65; P = 0.003) after follow-up even after adjustment for confounders.Conclusion: Weight gain since menopause is associated with body weight regain following the weight loss program. Therefore, weight gain since menopause should be considered as a factor influencing weight loss maintenance in older women.Keywords: obesity, body weight, weight regain, postmenopausal women, agin