Evolutionary and ecological significance of non-shivering thermogenesis in the common vole

La production endogène à long terme de chaleur, même au repos, est une adaptation que l'on retrouve chez les animaux à sang chaud (les oiseaux et les mammifères). Cette production de chaleur a comme but le maintien d'une température constante du corps indépendamment de la température extérieure. A cette fin, les mammifères ont développé une forme de tissu spécialisé nommé tissu adipeux brun (BAT). Ce tissu est responsable de la conversion de nourriture en chaleur, procédé appelé thermogenèse sans frisson (NST = non-shivering thermogenesis). Durant ce procédé la uncoupling protein 1 (UCP1) convertit, au sein des mitochondries, la nourriture en chaleur au lieu de produire de l'ATP, molécule utilisée comme énergie cellulaire. On suppose que cette inefficacité de la conversion de la nourriture en ATP dans le BAT influence l'homéostasie de l'énergie, l'allocation des ressources ainsi que la régulation de processus gourmant en énergie comme la croissance et la reproduction. Afin de maintenir une température du corps constante, les mammifères doivent ajuster leur NST en fonction de la température ambiante. La NST devrait être donc plus importante que la croissance et la reproduction durant l'hiver que lors l'été/à haute altitude qu'à basse altitude. En effet, plusieurs études ont déjà démontré la dépendance de la NST aux divers paramètres environnementaux. Par contre, l'héritabilité de la NST ainsi que sa relation avec d'autres traits de caractère, ne sont que très peu connus, ceci malgré l'importance d'une telle information afin de pouvoir comprendre son potentiel évolutif. L'étude de l'importance évolutive et écologique sur la NST chez les campagnols des champs (Microtus arvalis) fut donc le but cette thèse de doctorat. Grâce aux informations collectées sur 4 générations de campagnols (chapitre 1), une dépendance saisonnière et journalière de la NST a été démontrée: elle augmente lors des périodes froides et diminue lors de la lactation. On a démontré que bien qu'étant plastique, la variation de la NST a une composante génétique significative. Elle est corrélée avec le taux d'activité métabolique au repos indiquant des contraintes intrinsèques. A l'aide d'une expérience de jardin commune, on a pu démontrer dans le chapitre 2 que les campagnols habitant en altitude ont une capacité génétique de thermogenèse sans frisson plus haute que celles de basse altitude. Ils produisent des portées plus petites et leur descendance grandit moins vite, surtout à partir du 10ème jour ce qui coïncide avec le début de la production de chaleur endogène. En choisissant artificiellement des campagnols avec une NST faible ou grande, on a pu démontrer une relation entre la NST et la développement de la masse corporelle. Les campagnols avec une haute NST grandissent plus lentement et sont plus légères à l'âge adulte que celles ayant une basse NST. A l'aide d'un croisement interligne entre les campagnols sélectionnés (avec basse et haute NST), on a pu montrer dans le chapitre 3 des effets « parent-of-origin >> du développement massique de la descendance, indiquant une empreinte génétique parentale. Cela veut dire que l'expression d'un allele dépend de l'origine parentale. De plus, des effets « parent-of-origin » des taux de base de norépinephrine et d'irisine ont pu être trouvés. Ces hormones sont connues pour influencer non seulement la TSF mais aussi d'autres caractéristiques. Ces influences ouvrent la voie à de nouvelles études sur la relation entre la TSF et l'histoire de vie. Dans le chapitre 4 on a démontré des effets à long terme de l'allocation des ressources en manipulant la taille des portées qui ont abouti à des différences dans l'investissement dans la reproduction et de la croissance de la descendance à la fois dans le cas de la reproduction manipulé et aussi dans le non - manipulée entre les femelles avec portées agrandies et réduites. Ensemble, ces résultats mettent en évidence le rôle central de la NST dans l'allocation des ressources sur la base d'un compromis entre le maintien et la croissance et ainsi transforme l'histoire de vie des mammifères. Ces études montrent comment les mammifères peuvent répondre rapidement à court et à long terme (c'est-à-dire par des réponses génétiques ou plastiques) à un changement rapide du climat. On montre aussi qu'il y a probablement une corrélation entre l'histoire de vie et des changements du comportement. Finalement mes résultats ont montré un lien étroit entre la NST et la croissance et les dimensions du corps. Ces résultats indiquent que le tissu adipeux brun et la NST pourraient être une cible thérapeutique intéressante pour traiter l'obésité.

Recent human-induced trophic change in the large and deep perialpine Lake Lucerne (Switzerland) compared to historical geochemical variations

This study investigates the sedimentological and geochemical changes that occurred during the last 2200 years in the meromictic Lake Lucerne (Switzerland), one of the largest freshwater lakes of Central Europe. The stable isotope composition (delta C-13 and delta O-18 values) of bulk carbonates is compared to changes in grain-size distribution (clay and silt fraction), natural trace element input (titanium and thorium concentrations), and organic material abundance (C-org, nitrogen and phosphorus) and composition (C/N ratios and hydrogen and oxygen indexes). A drop in carbonate accumulation and in the delta O-18 values of sediments between ca. AD 500 and 700 followed a large and consistent rise in chemical weathering, marked by increases in the silicate-clay fraction and in crustal element concentrations. During the following millennium, there was a long-term decreasing trend in the lithogenic trace element input and in the phosphorus loading, suggesting decreasing terrigeneous input from runoff water. The major sedimentological change over the studied period occurred after ca. AD 1800 with a significant increase in the erosion-driven silt-fraction and in the sedimentation rate. During the last century, human-induced increase in nutrient input to the lake highly enhanced the accumulation of organic matter in sediment. Changes in nutrients and oxygen conditions in the hypolimnion of Lake Lucerne during the eutrophication period (i.e., the last 40 years) highly modified the geochemical fluxes compared to the relatively stable oligotrophic conditions that prevailed during the previous 2000 years. Before the 19th century, climate driven meromixis had a limited impact on the organic matter flux to the sediments, but the accumulation of carbonate considerably decreased during periods of lower mechanical erosion rates and high chemical weathering rates. (C) 2012 Elsevier B.V. All rights reserved.

Mutual trust and cooperation in the evolutionary hawks-doves game

Using a new dynamical network model of society in which pairwise interactions are weighted according to mutual satisfaction, we show that cooperation is the norm in the hawks-doves game when individuals are allowed to break ties with undesirable neighbors and to make new acquaintances in their extended neighborhood. Moreover, cooperation is robust with respect to rather strong strategy perturbations. We also discuss the empirical structure of the emerging networks, and the reasons that allow cooperators to thrive in the population. Given the metaphorical importance of this game for social interaction, this is an encouraging positive result as standard theory for large mixing populations prescribes that a certain fraction of defectors must always exist at equilibrium.

Chromosomal versus mitochondrial DNA evolution: tracking the evolutionary history of the southwestern european populations of the Sorex araneus group (Mammalia Insectivora)

The shrews of the Sorer araneus group have undergone a spectacular chromosome evolution. The karyotype of Sorer granarius is generally considered ancestral to those of Sorer coronatus and S. araneus. However, a sequence of 777 base pairs of the cytochrome b gene of the mitochondrial DNA (mtDNA) produces a quite different picture: S. granarius is closely related to the populations of S. araneus from the Pyrenees and from the northwestern Alps, whereas S. coronatus and S. araneus from Italy and the southern Alps represent two well-separated lineages. It is suggested that mtDNA and chromosomal evolution are in this case largely independant processes. Whereas mtDNA haplotypes are closely linked to the geographical history of the populations, chromosomal mutations were probably transmitted from one population to another. Available data suggest that the impressive chromosome polymorphism of this group is quite a recent phenomenon.

Which change talk dimensions are associated with subsequent drinking among young men receiving a brief motivational intervention in a non-clinical setting?

Background: Patient change talk (CT) during brief motivational interventions (BMI) has been linked with subsequent changes in drinking in clinical settings but this link has not been clearly established among young people in non-clinical populations. Objective: To determine which of several CT dimensions assessed during an effective BMI delivered in a non-clinical setting to 20-year old men are associated with drinking 6 months later. Methods: Of 125 individuals receiving a face-to-face BMI session (15.8 ± 5.4 minutes), we recorded and coded a subsample of 42 sessions using the Motivational Interviewing Skill Code 2.1. Each patient change talk utterance was categorized as `Reason´, `Ability´, `Desire´, `Need´, `Commitment´, `Taking steps´, or `Other´. Each utterance was graded according to its strength (absolute value from 1 to 3) and direction (i.e. towards (positive sign) or away (negative sign) from change/in favor of status quo). `Ability´, `Desire´, and `Need´ to change (`ADN´) were grouped together since these codes were too scarce to conduct analyses. Mean strength scores over the entire session were computed for each dimension and later dichotomized in towards change (i.e. mean core > 0) and away from change/in favor of status quo. Negative binomial regression models were used to assess the relationship between CT dimensions and drinking 6 months later, adjusting for drinking at baseline. Results: Compared to subjects with a `Taking steps´ score away from change/in favor of status quo, subjects with a positive `Taking steps´ score reported significantly less drinking 6 months later (Incidence Rate Ration [IRR] for drinks per week: 0.56, 95% Confidence Interval [CI] 0.31, 1.00). IRR (95%CI) for subjects with a positive `ADN´ score was 0.58, (0.32, 1.03). For subjects with a positive `Reason´, `Commitment´, and `Other´ scores, IRR (95%CI) were 1.28 (0.77; 2.12) 1.63 (0.85; 3.14) and 1.03 (0.61; 1.72), respectively. Conclusion: A change talk dimension reflecting steps taken towards change (`Taking steps´) is associated with less drinking 6 months later among young men receiving a BMI in a non-clinical setting. Encouraging patients to take steps towa change may be a worthy objective for clinicians and may explain BMI efficacy.

Estimating slope and level change in N=1 designs

The current study proposes a new procedure for separately estimating slope change and level change between two adjacent phases in single-case designs. The procedure eliminates baseline trend from the whole data series prior to assessing treatment effectiveness. The steps necessary to obtain the estimates are presented in detail, explained, and illustrated. A simulation study is carried out to explore the bias and precision of the estimators and compare them to an analytical procedure matching the data simulation model. The experimental conditions include two data generation models, several degrees of serial dependence, trend, level and/or slope change. The results suggest that the level and slope change estimates provided by the procedure are unbiased for all levels of serial dependence tested and trend is effectively controlled for. The efficiency of the slope change estimator is acceptable, whereas the variance of the level change estimator may be problematic for highly negatively autocorrelated data series.

Predictive value of readiness, importance, and confidence in ability to change drinking and smoking.

BACKGROUND: Visual analog scales (VAS) are sometimes used to assess change constructs that are often considered critical for change. Aims of Study: 1.) To determine the association of readiness to change, importance of changing and confidence in ability to change alcohol and tobacco use at baseline with the risk for drinking (more than 21 drinks per week/6 drinks or more on a single occasion more than once per month) and smoking (one or more cigarettes per day) six months later. 2.) To determine the association of readiness, importance and confidence with alcohol (number of drinks/week, number of binge drinking episodes/month) and tobacco (number of cigarettes/day) use at six months. METHODS: This is a secondary analysis of data from a multi-substance brief intervention randomized trial. A sample of 461 Swiss young men was analyzed as a prospective cohort. Participants were assessed at baseline and six months later on alcohol and tobacco use, and at baseline on readiness to change, importance of changing and confidence in ability to change constructs, using visual analog scales ranging from 1-10 for drinking and smoking behaviors. Regression models controlling for receipt of brief intervention were employed for each change construct. The lowest level (1-4) of each scale was the reference group that was compared to the medium (5-7) and high (8-10) levels. RESULTS: Among the 377 subjects reporting unhealthy alcohol use at baseline, mean (SD) readiness, importance and confidence to change drinking scores were 3.9 (3.0), 2.7 (2.2) and 7.2 (3.0), respectively. At follow-up, 108 (29%) reported no unhealthy alcohol use. Readiness was not associated with being risk-free at follow-up, but high importance (OR 2.94; 1.15, 7.50) and high confidence (OR 2.88; 1.46, 5.68) were. Among the 255 smokers at baseline, mean readiness, importance and confidence to change smoking scores were 4.6 (2.6), 5.3 (2.6) and 5.9 (2.7), respectively. At follow-up, 13% (33) reported no longer smoking. Neither readiness nor importance was associated with being a non-smoker, whereas high confidence (OR 3.29; 1.12, 9.62) was. CONCLUSIONS: High confidence in ability to change was associated with favorable outcomes for both drinking and smoking, whereas high importance was associated only with a favorable drinking outcome. This study points to the value of confidence as an important predictor of successful change for both drinking and smoking, and shows the value of importance in predicting successful changes in alcohol use. TRIAL REGISTRATION NUMBER: ISRCTN78822107.

Reproductive bribing and policing as evolutionary mechanisms for the suppression of within-group selfishness.

We show that a new, simple, and robust general mechanism for the social suppression of within-group selfishness follows from Hamilton's rule applied in a multilevel selection approach to asymmetrical, two-person groups: If it pays a group member to behave selfishly (i.e., increase its share of the group's reproduction, at the expense of group productivity), then its partner will virtually always be favored to provide a reproductive "bribe" sufficient to remove the incentive for the selfish behavior. The magnitude of the bribe will vary directly with the number of offspring (or other close kin) potentially gained by the selfish individual and inversely with both the relatedness r between the interactants and the loss in group productivity because of selfishness. This bribe principle greatly extends the scope for cooperation within groups. Reproductive bribing is more likely to be favored over social policing for dominants rather than subordinates and as intragroup relatedness increases. Finally, analysis of the difference between the group optimum for an individual's behavior and the individual's inclusive fitness optimum reveals a paradoxical feedback loop by which bribing and policing, while nullifying particular selfish acts, automatically widen the separation of individual and group optima for other behaviors (i.e., resolution of one conflict intensifies others).

A new perspective on the evolutionary history of western European Sorex araneus group revealed by paternal and maternal molecular markers.

The species of the common shrew (Sorex araneus) group are morphologically very similar, but have undergone a spectacular chromosomal evolution. We investigate here the evolutionary history of the Sorex araneus group distributed in western Europe. In particular, we clarify the position of a difficult species, S. granarius, using sex-specific (mtDNA and Y-chromosome) markers. The karyotype of S. granarius is generally considered similar to the common ancestor of the restricted group considered here. The mtDNA data (1.4 kb) confirms the close relationship between S. granarius and S. araneus sensu stricto (hereafter S. araneus s.s.), but the Y-chromosome (3.4 kb) produces a quite different picture: S. granarius is closely related to another species, S. coronatus. Comparison of mtDNA and Y-chromosome phylogenies suggests that the genetic and chromosomal evolution in this group are disconnected processes. The evolutionary history of the south-western European populations of the S. araneus group can only be understood considering secondary contacts between taxa after their divergence, implying genetic exchanges by means of hybridization and/or introgression.

Functional homogenization of bumblebee communities in alpine landscapes under projected climate change

Background: Bumblebees represent an active pollinator group in mountain regions and assure the pollination of many different plant species from low to high elevations. Plant-pollinator interactions are mediated by functional traits. Shift in bumblebee functional structure under climate change may impact plant-pollinator interactions in mountains. Here, we estimated bumblebee upward shift in elevation, community turnover, and change in functional structure under climate change. Method: We sampled bumblebee species at 149 sites along the elevation gradient. We used stacked species distribution models (S-SDMs) forecasted under three climate change scenarios (A2, A1B, RCP3PD) to model the potential distribution of the Bombus species. Furthermore, we used species proboscis length measurements to assess the functional change in bumblebee assemblages along the elevation gradient. Results: We found species-specific response of bumblebee species to climate change. Species differed in their predicted rate of range contraction and expansion. Losers were mainly species currently restricted to high elevation. Under the most severe climate change scenarios (A2), we found a homogenization of proboscis length structure in bumblebee communities along the elevation gradient through the upward colonization of high elevation by species with longer proboscides. Conclusions: Here, we show that in addition to causing the shift in the distribution of bumblebee species, climate change may impact the functional structure of communities. The colonization of high elevation areas by bumblebee species with long proboscides may modify the structure of plant-pollination interaction networks by increasing the diversity of pollination services at high elevation.