Demographic and genetic factors shaping contemporary metapopulation effective size and its empirical estimation in salmonid fish.

The preservation of biodiversity requires an understanding of the maintenance of its components, including genetic diversity. Effective population size determines the amount of genetic variance maintained in populations, but its estimation can be complex, especially when populations are interconnected in a metapopulation. Theory predicts that the effective size of a metapopulation (meta-N(e)) can be decreased or increased by population subdivision, but little empirical work has evaluated these predictions. Here, we use neutral genetic markers and simulations to estimate the effective size of a putative metapopulation in Atlantic salmon (Salmo salar). For a weakly structured set of rivers, we find that meta-N(e) is similar to the sum of local deme sizes, whereas higher genetic differentiation among demes dramatically reduces meta-N(e) estimates. Interdemic demographic processes, such as asymmetrical gene flow, may explain this pattern. However, simulations also suggest that unrecognized population subdivision can also introduce downward bias into empirical estimation, emphasizing the importance of identifying the proper scale of distinct demographic and genetic processes. Under natural patterns of connectivity, evolutionary potential may generally be maintained at higher levels than the local population, with implications for conservation given ongoing species declines and habitat fragmentation.

Patterns of coral-dinoflagellate associations in Acropora: significance of local availability and physiology of Symbiodinium strains and host-symbiont selectivity.

Like other reef-building corals, members of the genus Acropora form obligate endosymbioses with dinoflagellates (zooxanthellae) belonging to the genus Symbiodinium. Both Symbiodinium and its hosts are diverse assemblages, and the relationships between host and algal genotypes are unclear. In this study, we determined phylogenetic relationships between Symbiodinium isolates from a wide range of Acropora species and plotted the algal genotypes onto a molecular phylogeny of 28 Acropora species, using the same samples for the host and symbiont genotyping. In addition, we performed a preliminary survey of zooxanthella distribution in Acropora species from the central Great Barrier Reef. Three of the four known major zooxanthellae clades were represented in the 168 samples examined, and within the major clade C, three distinct subclades were identified. No evidence was found for coevolution, but several clear patterns of specificity were identified. Moreover, composition of the zooxanthella pool varied among locales and in one host species we found light-related patterns of zooxanthella distribution.

Social valorisation of stoutness as a determinant of obesity in the context of nutritional transition in Cameroon: the Bamiléké case.

Body size perceptions were assessed among members of the Bamiléké, an ethnic group in an urban setting in Cameroon with high rates of obesity, but also a positive perception of stoutness in its social representations. We first implemented a qualitative study (April 2007) to identify local representations of body weight among Bamiléké using semi-structured interviews. We then quantitatively assessed body size perceptions among a representative sample of Bamiléké (May to June 2007), employing a body image assessment scale and a questionnaire that included declarative body weight self-satisfaction, health status, and attempts to reduce weight. Results indicate Desired Body Size (DBS) for women, and particularly for men, was situated in the overweight category. Qualitative analyses show that overweight is considered as a normal and healthy body size in the Bamiléké. On the other hand, the quantitative study reveals that high rates of obesity, especially in women (40.8% obese), are associated with high blood pressure. Moreover, subjects who had a negative perception of their health status wanted to lose weight (p < 0.01). Unlike males, females have a DBS lower than their Current Body Size (p < 0.001). In addition, subjects (particularly males) who felt they were too lean, were older than those who felt too fat. We therefore conclude that the social valorisation of stoutness exposes Bamiléké, particularly males, to obesity. Although the women stated a desire to lose weight and present aesthetic criteria more oriented towards slimness, the attitude of the Bamiléké remained oriented toward stoutness appreciation. This preference can help protect against body image disturbances identified in Western societies, but may also increase of the incidence of obesity and its associated pathologies in this part of the world.