Bone turnover markers in HIV-infected patients before starting antiretroviral therapy.

Purpose: Bone turnover markers (BTM) - aminoterminal propeptide of type 1 collagen (P1NP) and C-terminal telopeptide of type 1 collagen (b-CTX) - are related to bone density and fracture risk. A high prevalence of osteopenia/osteoporosis and hypovitaminosis D has been reported in HIV patients, however there are few data about BTM in this population. Our aim was to analyse the prevalence of elevated serum levels of BTM in HIV patients before starting antiretroviral therapy (ART), and related factors. Methods: Cross-sectional study of a series of HIV-patients who started ART during June/11-June/12 in our hospital. Patients with presence of diseases or treatments known to affect bone metabolism were excluded. Epidemiological, clinical, and immunovirological data in addition to serum fasting levels of glucose, lipid profile, calcium, phosphate, alkaline phosphatase, 25-hydroxyvitamin D3 (25OHD), parathyroid hormone (PTH), P1NP, and β-CTX were collected. Definitions: hypovitaminosis D if 25OHD<30 ng/ml, vitamin D deficiency if 25OHD<20 ng/ml; elevated levels of BTM if β-CTX (ng/ml) >0.64 (men<70 years),>0.85 (men>70 years),>0.58 (pre-menopause women), >0.99 (post-menopause women), or P1NP (ng/mL)>69.4 (men<60 years), >71.1 (men>60 years), >55.7 (pre-menopause women), >61.2 (post-menopause women). Results: 47 patients were included, 91.5% men, median age 37.1 years (30.0-44.3), and 93.6% sexual transmission of HIV (34 HMX, 10 HTX). Median time since the diagnosis of HIV was 3.4 months (1.4- 31.7); there were 7 (14.9%) Aids cases, median CD4 count was 277/ mm3 (155-433), and HIV-VL 4.8 log10 (4.1-5.2). Median serum 25OHD was 29 mg/L (21.9-41.1), with a prevalence of hypovitaminosis of 52.2%, and deficiency of 17.4%. PTH was in range in all cases. Median serum P1NP was 33.3 ng/mL (24.5-52.5) and β-CTX 0.25 ng/mL (0.20-0.45); five (11.4%) patients presented high levels of BTM: 4 men, median age 37.1 years, median CD4 count 247/mm3, median HIV-VL 5.18 log10, and one with hypovitaminosis D. Elevated BTM were related with no clinical, analytical, immunovirological parameters nor with serum levels of 25OHD nor PTH. Conclusions: The prevalence of elevated BTM was high in this series of HIV-patients, mostly young men, with short time of HIV infection and with no immunovirologic control. BTM were related with no clinical nor analytical data.

Alterations in cytokines and haematological parameters during the acute and convalescent phases of Plasmodium falciparum and Plasmodium vivax infections

Haematological and cytokine alterations in malaria are a broad and controversial subject in the literature. However, few studies have simultaneously evaluated various cytokines in a single patient group during the acute and convalescent phases of infection. The aim of this study was to sequentially characterise alterations in haematological patters and circulating plasma cytokine and chemokine levels in patients infected with Plasmodium vivax or Plasmodium falciparum from a Brazilian endemic area during the acute and convalescent phases of infection. During the acute phase, thrombocytopaenia, eosinopaenia, lymphopaenia and an increased number of band cells were observed in the majority of the patients. During the convalescent phase, the haematologic parameters returned to normal. During the acute phase, P. vivax and P. falciparum patients had significantly higher interleukin (IL)-6, IL-8, IL-17, interferon-γ, tumour necrosis factor (TNF)-α, macrophage inflammatory protein-1β and granulocyte-colony stimulating factor levels than controls and maintained high levels during the convalescent phase. IL-10 was detected at high concentrations during the acute phase, but returned to normal levels during the convalescent phase. Plasma IL-10 concentration was positively correlated with parasitaemia in P. vivax and P. falciparum-infected patients. The same was true for the TNF-α concentration in P. falciparum-infected patients. Finally, the haematological and cytokine profiles were similar between uncomplicated P. falciparum and P. vivax infections.

Influence of age on the haemoglobin concentration of malaria-infected patients in a reference centre in the Brazilian Amazon

Anaemia is amongst the major complications of malaria, a major public health problem in the Amazon Region in Latin America. We examined the haemoglobin (Hb) concentrations of malaria-infected patients and compared it to that of malaria-negative febrile patients and afebrile controls. The haematological parameters of febrile patients who had a thick-blood-smear performed at an infectious diseases reference centre of the Brazilian Amazon between December 2009-January 2012 were retrieved together with clinical data. An afebrile community control group was composed from a survey performed in a malaria-endemic area. Hb concentrations and anaemia prevalence were analysed according to clinical-epidemiological status and demographic characteristics. In total, 7,831 observations were included. Patients with Plasmodium falciparum infection had lower mean Hb concentrations (10.5 g/dL) followed by P. vivax-infected individuals (12.4 g/dL), community controls (12.8 g/dL) and malaria-negative febrile patients (13.1 g/dL) (p < 0.001). Age, gender and clinical-epidemiological status were strong independent predictors for both outcomes. Amongst malaria-infected individuals, women in the reproductive age had considerably lower Hb concentrations. In this moderate transmission intensity setting, both vivax and falciparum malaria are associated with reduced Hb concentrations and risk of anaemia throughout a wide age range.

Community introduction of practice parameters for autistic spectrum disorders: Advancing early recognition.

OBJECTIVES: Within a strong interdisciplinary framework, improvement in the quality of care for children with autistic spectrum disorders through a 2 year implementation program of Practice Parameters, aimed principally at improving early detection and intervention. METHOD: We developed Practice Parameters (PPs) for Pervasive Developmental Disorders and circulated the PPs to all child and adolescent psychiatrists practicing in the region. RESULTS: PP development and parallel information strategies resulted in a significant decrease of 1.5 years in the mean-age-at-diagnosis. However, further analysis indicated that improvement was only transient. CONCLUSION: Despite the encouraging improvement in mean-age-at-diagnosis 2 years after PP implementation, other indicators showed a failure to maintain the improvements. A systematic screening program would be the most reliable method to reinforce the PPs.

Is there an efficient trap or collection method for sampling Anopheles darlingi and other malaria vectors that can describe the essential parameters affecting transmission dynamics as effectively as human landing catches? - A Review

Distribution, abundance, feeding behaviour, host preference, parity status and human-biting and infection rates are among the medical entomological parameters evaluated when determining the vector capacity of mosquito species. To evaluate these parameters, mosquitoes must be collected using an appropriate method. Malaria is primarily transmitted by anthropophilic and synanthropic anophelines. Thus, collection methods must result in the identification of the anthropophilic species and efficiently evaluate the parameters involved in malaria transmission dynamics. Consequently, human landing catches would be the most appropriate method if not for their inherent risk. The choice of alternative anopheline collection methods, such as traps, must consider their effectiveness in reproducing the efficiency of human attraction. Collection methods lure mosquitoes by using a mixture of olfactory, visual and thermal cues. Here, we reviewed, classified and compared the efficiency of anopheline collection methods, with an emphasis on Neotropical anthropophilic species, especially Anopheles darlingi, in distinct malaria epidemiological conditions in Brazil.

Assisted reproductive technology and obstetric outcome in couples when the male partner has a chronic viral disease.

BACKGROUND Assisted reproductive technology (ART) with washed semen can achieve pregnancy with minimal risk of horizontal and vertical transmission of chronic viral diseases (CVD) such as human immunodeficiency virus (HIV), hepati- tis C virus (HCV) and hepatitis B virus (HBV) among serodiscordant couples. How- ever, few studies have been made of the use made by these couples of ARTs or of the obstetric results achieved. MATERIALS AND METHODS In this retrospective study, 93 men who were seropositive for HIV, HCV or HBV and who underwent assisted reproduction treatment at our centre (Hospital Universitario Virgen de las Nieves, Granada, Spain) were included. Washed semen was tested to detect viral particles. Non-infected women were tested before and after each treatment, as were the neonates at birth and after three months. RESULTS A total of 62 sperm samples were washed, and none were positive for the detec- tion of viral molecules. Semen samples from 34 HBV positive males were not washed since the female partner had immunity to hepatitis B. In total, 38 clinical pregnancies were achieved (22% per cycle and 40.9% per couple) out of 173 cycles initiated, and 28 births were achieved (16.2% per cycle and 30.1% per couple), producing 34 live births. The rate of multiple pregnancies was 21.4%. Obstetric and neonatal results were similar in the groups of couples studied. At follow-up, no seroconversion was detected in the women or neonates. CONCLUSION Sperm washing and intracytoplasmic sperm injection are shown to be a safe and effective option for reducing the risk of transmission or super infection in serodiscordant or concordant couples who wish to have a child. Pregnancies ob- tained by ART in couples when the male is CVD infected achieve good obstetric and neonatal results.

Activated protein C consumption and coagulation parameters in severe sepsis and septic shock.

Introduction Activated protein C (APC) deC ciency is prevalent in severe sepsis and septic shock patients. The aim of the study was to relate the anticoagulation activity evaluated by APC with other coagulation parameters adjusted to 28-day mortality. Methods A cohort study of 150 critically ill adults. Age, sex, sources of infection and coagulation markers within 24< hours from severe sepsis or septic shock onset, deC ned according to Surviving Sepsis Campaign (SSC) criteria, were studied. We analyzed APC activity using a hemostasis laboratory analyzer (BCS® XP; Siemens). A descriptive and comparative statistical analysis was performed using SPSS version 15.0 (SPSS Inc., Chicago, IL, USA). Results We analyzed 150 consecutive episodes of severe sepsis (16%) or septic shock (84%) admitted to the UCI. The median age of the study sample was 64 (interquartile range (IQR): 22.30.001). See Figure 1. Conclusion Low levels of PC are associated with poor outcome and severity in severe sepsis, and it is well correlated with antithrombin III and INR.

Variation of transaminases, HCV-RNA levels and Th1/Th2 cytokine production during the post-partum period in pregnant women with chronic hepatitis C.

This study analyses the evolution of liver disease in women with chronic hepatitis C during the third trimester of pregnancy and the post-partum period, as a natural model of immune modulation and reconstitution. Of the 122 mothers recruited to this study, 89 were HCV-RNA+ve/HIV-ve and 33 were HCV-RNA-ve/HIV-ve/HCVantibody+ve and all were tested during the third trimester of pregnancy, at delivery and post-delivery. The HCV-RNA+ve mothers were categorized as either Type-A (66%), with an increase in ALT levels in the post-partum period (>40 U/L; P<0.001) or as Type-B (34%), with no variation in ALT values. The Type-A mothers also presented a significant decrease in serum HCV-RNA levels in the post-delivery period (P<0.001) and this event was concomitant with an increase in Th1 cytokine levels (INFγ, P = 0.04; IL12, P = 0.01 and IL2, P = 0.01). On the other hand, the Type-B mothers and the HCV-RNA-ve women presented no variations in either of these parameters. However, they did present higher Th1 cytokine levels in the partum period (INFγ and IL2, P<0.05) than both the Type-A and the HCV-RNA-ve women. Cytokine levels at the moment of delivery do not constitute a risk factor associated with HCV vertical transmission. It is concluded that differences in the ALT and HCV-RNA values observed in HCV-RNA+ve women in the postpartum period might be due to different ratios of Th1 cytokine production. In the Type-B women, the high partum levels of Th1 cytokines and the absence of post-partum variation in ALT and HCV-RNA levels may be related to permanent Th1 cytokine stimulation.

Strong reproductive barriers in a narrow hybrid zone of West-Mediterranean green toads (Bufo viridis subgroup) with Plio-Pleistocene divergence

Background One key question in evolutionary biology deals with the mode and rate at which reproductive isolation accumulates during allopatric speciation. Little is known about secondary contacts of recently diverged anuran species. Here we conduct a multi-locus field study to investigate a contact zone between two lineages of green toads with an estimated divergence time of 2.7 My, and report results from preliminary experimental crosses. Results The Sicilian endemic Bufo siculus and the Italian mainland-origin B. balearicus form a narrow hybrid zone east of Mt. Etna. Despite bidirectional mtDNA introgression over a ca. 40 km North-South cline, no F1 hybrids could be found, and nuclear genomes display almost no admixture. Populations from each side of the contact zone showed depressed genetic diversity and very strong differentiation (FST = 0.52). Preliminary experimental crosses point to a slightly reduced fitness in F1 hybrids, a strong hybrid breakdown in backcrossed offspring (F1 x parental, with very few reaching metamorphosis) and a complete and early mortality in F2 (F1 x F1). Conclusion Genetic patterns at the contact zone are molded by drift and selection. Local effective sizes are reduced by the geography and history of the contact zone, B. balearicus populations being at the front wave of a recent expansion (late Pleistocene). Selection against hybrids likely results from intrinsic genomic causes (disruption of coadapted sets of genes in backcrosses and F2-hybrids), possibly reinforced by local adaptation (the ranges of the two taxa roughly coincide with the borders of semiarid and arid climates). The absence of F1 in the field might be due to premating isolation mechanisms. Our results, show that these lineages have evolved almost complete reproductive isolation after some 2.7 My of divergence, contrasting sharply with evidence from laboratory experiments that some anuran species may still produce viable F1 offspring after > 20 My of divergence.

Assessment of liver tumor response by high-field (3T) MRI after radiofrequency ablation: Short- and mid-term evolution of diffusion parameters within the ablation zone.

PURPOSE: To compare the apparent diffusion coefficient (ADC) values of malignant liver lesions on diffusion-weighted MRI (DWI) before and after successful radiofrequency ablation (RF ablation). MATERIALS AND METHODS: Thirty-two patients with 43 malignant liver lesions (23/20: metastases/hepatocellular carcinomas (HCC)) underwent liver MRI (3.0T) before (<1month) and after RF ablation (at 1, 3 and 6months) using T2-, gadolinium-enhanced T1- and DWI-weighted MR sequences. Jointly, two radiologists prospectively measured ADCs for each lesion by means of two different regions of interest (ROIs), first including the whole lesion and secondly the area with the visibly most restricted diffusion (MRDA) on ADC map. Changes of ADCs were evaluated with ANOVA and Dunnett tests. RESULTS: Thirty-one patients were successfully treated, while one patient was excluded due to focal recurrence. In metastases (n=22), the ADC in the whole lesion and in MRDA showed an up-and-down evolution. In HCC (n=20), the evolution of ADC was more complex, but with significantly higher values (p=0.013) at 1 and 6months after RF ablation. CONCLUSION: The ADC values of malignant liver lesions successfully treated by RF ablation show a predictable evolution and may help radiologists to monitor tumor response after treatment.

Coupled reproductive ecologies in a plant-pollinator-seed predator system

Résumé de la thèseBien que le mutualisme puisse être considéré comme une relation harmonieuse entre différentes espèces, son étude révèle plutôt une exploitation réciproque où chaque partenaire tente de maximiser ses bénéfices tout en réduisant ses coûts. Dans ce contexte, l'identification des facteurs qui favorisent ou contrarient, au cours de l'évolution, une issue mutualiste est une étape majeure pour pouvoir reconstruire les étapes clés menant à l'apparition et au maintien des interactions mutualistes. Le but de ce doctorat était l'identification des traits phénotypiques qui permettent à la plante Silene latofolia (Caryophyllacée)et à son pollinisateur - prédateur de graines, la phalène Hadena bicruris (Noctuidé), d'augmenter les bénéfices nets que chacun retire de l'interaction. Ce système d'étude est particulièrement bien approprié à l'étude de ces traits, car on peut assez facilement estimer la qualité et la quantité des descendants (fitness) des deux partenaires. En effet, la femelle papillon pond un oeuf dans la fleur qu'elle pollinise et sa larve se développe dans le fruit, consommant les graines de la plante. Ainsi, sur une même plante, il est possible d'estimer les succès respectifs de la plante et du papillon à obtenir une descendance. De plus, le conflit d'intérêt autour des graines qui sont indispensables, à la fois à la plante et au papillon, peut stimuler l'évolution de traits qui limitent la surexploitation réciproque des partenaires. Dans une première étude, j'ai montré que le papillon mâle était un pollinisateur efficace de S. latifolia et qu'ainsi, il permettait à la plante d'augmenter le nombre de graines produites (i.e.bénéfice) sans pour autant augmenter la quantité de larves sur la plante. Dans ce système, les papillons pondent un seul oeuf par fleur, déposé soit à l'intérieur de la fleur, dans le tube de corolle, soit sur le pétale. Ma seconde étude montre que les plantes répondent différemment à la présence des oeufs suivant leur position. Aussi, quand l'oeuf est placé dans la fleur, la plante a davantage tendance à ne pas développer le fruit de la fleur infesté ou bien à produire des fruits plus petits que lorsque l'oeuf est placé sur le pétale. Enfin, j'ai montré que la femelle du papillon pond plus souvent sur le pétale lorsque elle visite des fleurs dotées d'un long tube de corolle, et que les larves issues de ces oeufs ont moins de chances de réussir à pénétrer dans le fruit que les larves issues des oeufs placés à l'intérieur de la fleur. Aussi, la variation observée du site de ponte pourrait être causé par la morphologie de la fleur qui contraint le papillon à pondre sur le pétale. Vu dans leur ensemble, les résultats obtenus pendant ce doctorat suggèrent que la participation des mâles à la pollination, l'absence de développement des fruits et la profondeur du tube de corolle pourraient réduire les coûts que S. latifolia subit dans son interaction avec H. bicruris. Par ailleurs, je n'ai pas détecté de mécanismes qui permettraient au papillon de réduire les coûts que la plante pourrait lui imposer. La prochaine étape serait de déterminer l'effet des traits identifiés dans ce doctorat sur la fitness globale de la plante et du papillon pour estimer pleinement leur efficacité à réduire les coûts et à favoriser une issue mutualiste. De même, il faudrait évaluer l'effet de ces traits en populations naturelles pour identifier le rôle des facteurs environnementaux sur leur efficacité.AbstractAlthough mutualisms can be regarded as harmonious relationships between the interacting partners, they are best conceptualized as reciprocal exploitations in which each partner attempts to increase its own benefits and decrease its costs. To date, identifying the factors which promote or discourage mutualistic outcomes remains a major goal to reconstruct the ecological conditions leading to mutualisms. The aim of this PhD thesis was to identify phenotypic traits that may increase the net benefits of each partner in the interaction between the plant Silene latifolia (Caryophyllaceae) and its pollinator / seed predator, the moth Hadena bicruris (Noctuidae). This study system is particularly well suited because the fitness of both interacting species can be assessed. The female moth lays its egg in the flower it pollinated, and its offspring grows in the fruit, feeding on the seeds of the plant, which allows for the follow-up of both larva and fruit fates. Furthermore, the inherent conflict of interest over the seeds as plant progeny vs. larval resource may stimulate the evolution of traits that reduce overexploitation in both the moth and plant. In a first study, I show that male moths are efficient pollinators, hence increasing seed production without increasing oviposition. The contribution of male moths to pollination might thus improve the net benefits of the interaction for the host plant. Females of the H. bicruris moth lay a single egg per flower, and place it either inside the corolla tube or on the petal. My second study shows that plants are more likely to abort the infested flower or to produce a smaller fruit when the egg was experimentally placed inside the flower compared to plants that received an egg on the petal. Finally, female moths were found to lay their eggs more frequently on the petal when visiting a flower with a deep corolla tube, and larvae hatching from these eggs less likely to successfully attack the fruit. Variation in egg position on the flower may thus be the result of a constraint imposed by floral morphology. Overall, this PhD work suggests that the pollination by male moths, flower abortion, and deep corolla tube may efficiently reduce the costs experienced by S. latifolia in its interaction with H. bicruris. Interestingly, no apparent mechanism of costs reduction was detected for the moth. Further studies should focus on the effects of these traits (i) in the long term fitness of both the plant and the insect and (ii) their interactions with environmental factors (biotic and abiotic) that may affect their efficiency in natural populations.

Massive nest-box supplementation boosts fecundity, survival and even immigration without altering mating and reproductive behaviour in a rapidly recovered bird population.

Habitat restoration measures may result in artificially high breeding density, for instance when nest-boxes saturate the environment, which can negatively impact species' demography. Potential risks include changes in mating and reproductive behaviour such as increased extra-pair paternity, conspecific brood parasitism, and polygyny. Under particular cicumstances, these mechanisms may disrupt reproduction, with populations dragged into an extinction vortex. With the use of nuclear microsatellite markers, we investigated the occurrence of these potentially negative effects in a recovered population of a rare secondary cavity-nesting farmland bird of Central Europe, the hoopoe (Upupa epops). High intensity farming in the study area has resulted in a total eradication of cavity trees, depriving hoopoes from breeding sites. An intensive nest-box campaign rectified this problem, resulting in a spectacular population recovery within a few years only. There was some concern, however, that the new, high artificially-induced breeding density might alter hoopoe mating and reproductive behaviour. As the species underwent a serious demographic bottleneck in the 1970-1990s, we also used the microsatellite markers to reconstitute the demo-genetic history of the population, looking in particular for signs of genetic erosion. We found i) a low occurrence of extra-pair paternity, polygyny and conspecific brood parasitism, ii) a high level of neutral genetic diversity (mean number of alleles and expected heterozygosity per locus: 13.8 and 83%, respectively) and, iii) evidence for genetic connectivity through recent immigration of individuals from well differentiated populations. The recent increase in breeding density did thus not induce so far any noticeable detrimental changes in mating and reproductive behaviour. The demographic bottleneck undergone by the population in the 1970s-1990s was furthermore not accompanied by any significant drop in neutral genetic diversity. Finally, genetic data converged with a concomitant demographic study to evidence that immigration strongly contributed to local population recovery.

Genetics of cadmium hyperaccumulation variance in Thlaspi caerulescens natural populations from Switzerland

SUMMARY Heavy metal presence in the environment is a serious concern since some of them can be toxic to plants, animals and humans once accumulated along the food chain. Cadmium (Cd) is one of the most toxic heavy metal. It is naturally present in soils at various levels and its concentration can be increased by human activities. Several plants however have naturally developed strategies allowing them to grow on heavy metal enriched soils. One of them consists in the accumulation and sequestration of heavy metals in the above-ground biomass. Some plants present in addition an extreme strategy by which they accumulate a limited number of heavy metals in their shoots in amounts 100 times superior to those expected for a non-accumulating plant in the same conditions. Understanding the genetic basis of the hyperaccumulation trait - particularly for Cd - remains an important challenge which may lead to biotechnological applications in the soil phytoremediation. In this thesis, Thlaspi caerulescens J. & C. Presl (Brassicaceae) was used as a model plant to study the Cd hyperaccumulation trait, owing to its physiological and genetic characteristics. Twenty-four wild populations were sampled in different regions of Switzerland. They were characterized for environmental and soil parameters as well as intrinsic characteristics of plants (i.e. metal concentrations in shoots). They were as well genetically characterized by AFLPs, plastid DNA polymorphism and genes markers (CAPS and microsatellites) mainly developed in this thesis. Some of the investigated genes were putatively linked to the Cd hyperaccumulation trait. Since the study of the Cd hyperaccumulation in the field is important as it allows the identification of patterns of selection, the present work offered a methodology to define the Cd hyperaccumulation capacity of populations from different habitats permitting thus their comparison in the field. We showed that Cd, Zn, Fe and Cu accumulations were linked and that populations with higher Cd hyperaccumulation capacity had higher shoot and reproductive fitness. Using our genetic data, statistical methods (Beaumont & Nichols's procedure, partial Mantel tests) were applied to identify genomic signatures of natural selection related to the Cd hyperaccumulation capacity. A significant genetic difference between populations related to their Cd hyperaccumulation capacity was revealed based on somè specific markers (AFLP and candidate genes). Polymorphism at the gene encoding IRTl (Iron-transporter also participating to the transport of Zn) was suggested as explaining part of the variation in Cd hyperaccumulation capacity of populations supporting previous physiological investigations. RÉSUMÉ La présence de métaux lourds dans l'environnement est un phénomène préoccupant. En effet, certains métaux lourds - comme le cadmium (Cd) -sont toxiques pour les plantes, les animaux et enfin, accumulés le long de la chaîne alimentaire, pour les hommes. Le Cd est naturellement présent dans le sol et sa concentration peut être accrue par différentes activités humaines. Certaines plantes ont cependant développé des stratégies leur permettant de pousser sur des sols contaminés en métaux lourds. Parmi elles, certaines accumulent et séquestrent les métaux lourds dans leurs parties aériennes. D`autres présentent une stratégie encore plus extrême. Elles accumulent un nombre limité de métaux lourds en quantités 100 fois supérieures à celles attendues pour des espèces non-accumulatrices sous de mêmes conditions. La compréhension des bases génétiques de l'hyperaccumulation -particulièrement celle du Cd - représente un défi important avec des applications concrètes en biotechnologies, tout particulièrement dans le but appliqué de la phytoremediation des sols contaminés. Dans cette thèse, Thlaspi caerulescens J. & C. Presl (Brassicaceae) a été utilisé comme modèle pour l'étude de l'hyperaccumulation du Cd de par ses caractéristiques physiologiques et génétiques. Vingt-quatre populations naturelles ont été échantillonnées en Suisse et pour chacune d'elles les paramètres environnementaux, pédologique et les caractéristiques intrinsèques aux plantes (concentrations en métaux lourds) ont été déterminés. Les populations ont été caractérisées génétiquement par des AFLP, des marqueurs chloroplastiques et des marqueurs de gènes spécifiques, particulièrement ceux potentiellement liés à l'hyperaccumulation du Cd (CAPS et microsatellites). La plupart ont été développés au cours de cette thèse. L'étude de l'hyperaccumulation du Cd en conditions naturelles est importante car elle permet d'identifier la marque, éventuelle de sélection naturelle. Ce travail offre ainsi une méthodologie pour définir et comparer la capacité des populations à hyperaccumuler le Cd dans différents habitats. Nous avons montré que les accumulations du Cd, Zn, Fe et Cu sont liées et que les populations ayant une grande capacité d'hyperaccumuler le Cd ont également une meilleure fitness végétative et reproductive. Des méthodes statistiques (l'approche de Beaumont & Nichols, tests de Martel partiels) ont été utilisées sur les données génétiques pour identifier la signature génomique de la sélection naturelle liée à la capacité d'hyperaccumuler le Cd. Une différenciation génétique des populations liée à leur capacité d'hyperaccumuler le Cd a été mise en évidence sur certains marqueurs spécifiques. En accord avec les études physiologiques connues, le polymorphisme au gène codant IRT1 (un transporteur de Fe impliqué dans le transport du Zn) pourrait expliquer une partie de la variance de la capacité des populations à hyperaccumuler le Cd.

Sex-biased dispersal in a migratory bat: a characterization using sex-specific demographic parameters.

We studied the noctule bat (Nyctalus noctula), in which the mitochondrial F(ST) is about 10 times that revealed by nuclear markers, to address two questions. We first verified whether random dispersal of one sex is compatible with highly contrasted mitochondrial and nuclear population structures. Using computer simulations, we then assessed the power of multilocus population differentiation tests when the expected population structure departs only slightly from panmixia. Using an island model with sex-specific demographic parameters, we found that random male dispersal is consistent with the population structure observed in the noctule. However, other parameter combinations are also compatible with the data. We computed the minimum sex bias in dispersal (at least 69% of the dispersing individuals are males), a result that would not be available if we had used more classical population genetic models. The power of multilocus population differentiation tests was unexpectedly high, the tests being significant in almost 100% of the replicates, although the observed population structure infered from nuclear markers was extremely low (F(ST) = 0.6%).