Inferring multilocal typologies of agrosystems and farmers' practices: A methodological basis for the setting of participatory breeding designs.

Family farms play an essential role in agroecological transition in Sahelian countries and worldwide. They present diversified features in terms of socio-economic organization, agrobiodiversity management and cropping systems diversity. Decentralized participatory breeding approaches aim to sustain the diversity of varieties adapted for such smallholder farmers' contexts. However the lack of clear target population of environments limits the focus and the efficiency of these approaches given the large diversification of the local contexts. In this study, we surveyed variables linked to agrosystems, crop management options and farmers' criteria of varietal evaluation from 254 family farms sampled along 13 locations spanning the target area of a decentralized participatory breeding program of cowpea crop (Vigna unguiculata L. Walp) in Niger. The objective of our study was to infer typologies of family farms in the study area based on relevant variables supporting the setting of target population of environments (TPEs) to be considered in the breeding program. We used factorial analysis of mixed data (FAMD) and the Discriminant Analysis of Principal Components (DAPC) to infer the clusters. Chi square test, analysis of variance and generalized linear model were used to identify key variables discriminating the clusters. These clusters were geographically mapped to analyze their multilocal distribution. So, we identified and characterized four clusters structuring the diversity of the local agrosystems (Typologie G), five clusters structuring the diversity of cowpea cropping management options (Typologie C) and five clusters structuring the diversity of criteria used by farmers to evaluate the performance of cowpea varieties in the local contexts (Typologie P). Typology G distinguished farms based on discriminating variables linked for instance to secondary activities, cultivated species, soil fertility management practices and farm resources including land and livestock. Typology C distinguished farms based on cowpea management pratices including the secondary crop intercropped with cowpea (sorghum, Guinea sorrel, sesame or groundnut) and the use of cowpea harvest products (seeds, haulms, hulls). Typology P was based on discriminating performance criteria including cycle length, insect resistance, striga resistance, drought resistance, haulm production and economic value of cowpea variety. This methodology provides a robust and replicable way for the definition of clusters capturing the diversity of farms and local contexts. We discussed the perspective of using these clusters to set target population of environments for decentralized breeding programs.

Prospective screening for significant liver fibrosis by fibrosis-4 in primary care patients without known liver disease.

BACKGROUND: Fibrosis-4 test (FIB-4) is one of the simplest, free of charge, noninvasive scoring tests. We aimed to prospectively measure the prevalence of liver fibrosis in adults with no previously known liver disease and who consulted a general practitioner by FIB-4 score; compare this test to an NAFLD Fibrosis Score (NFS) and Fibrometer (FM); explore the prevalence of risk factors (obesity, diabetes, alcohol, and hypertension) and reconsider a possible cause of liver disease in patients recognized as FIB-4-positive. METHODS: Over a 6-month period, 40 general practitioners (GPs) offered all their consecutive adult primary care patients with no previously known liver pathology and a liver fibrosis screening via a blood test of three scores. RESULTS: Among the consecutive 2121 patients included in the study, 39% had a BMI greater than 25 kg/m2, 13% had an alcohol consumption greater than 100 g/week, 10% had type 2 diabetes, and 29% had hypertension. The prevalence of significant liver fibrosis by FIB-4, according to age was 19.1% (95% confidence interval: 17.5-20.9%). By comparison, prevalence was 16.8% (15.0-18.5%) by the NFS and 8.2% (6.9-9.6%) by the FM. A significant relationship was observed between FIB-4 fibrosis risk stages and NFS and FM scores. GPs identified the cause of disease in 2/3 of FIB-4-positive cases, mainly nonalcoholic steatohepatitis. CONCLUSION: Liver fibrosis was suspected by FIB-4 score in 19.1% of patients with no previously known liver disease. The detection of significant fibrosis by the FIB-4 allowed the GP to suspect liver disease. The FIB-4 score that can be automatically generated should allow earlier recognition of liver disease in the general population.

Evolution of almond genetic diversity and farmer practices in Lebanon: impacts of the diffusion of a graft-propagated cultivar in a traditional system based on seed-propagation.

BACKGROUND: Under cultivation, many outcrossing fruit tree species have switched from sexual reproduction to vegetative propagation. Traditional production systems have persisted, where cultivar propagation is based on a mixed reproductive system. For millenia, almond, Prunus dulcis, has been propagated by seeds. Almond grafting remained of little importance until recently. In Lebanon, both sexual and clonal reproductions are used for almond propagation. We used 15 microsatellite markers to investigate the effect of introducing graft-propagated cultivars and associated practices, on the structure of the genetic diversity among and within the two main Lebanese cultivars. RESULTS: As expected, the sexually propagated cultivar Khachabi exhibited more genotypic and genetic diversity than the vegetatively propagated cultivar Halwani. It also exhibited lower differentiation among populations. The distribution of clones showed that propagation modes were not exclusive: farmers have introduced clonal propagation in the seed-propagated cultivar while they have maintained a diversity of genotypes within populations that were mostly graft-propagated. These practices are also important to avoid mate limitations that hamper fruit production in a self-incompatible species. 'Khachabi' is structured into two gene pools separated by the Lebanese mountains. As to 'Halwani', two different gene pools were introduced. The most ancient one shares the same geographic range as 'Khachabi'; longtime coexistence and sexual reproduction have resulted in admixture with 'Khachabi'. In contrast, the more recent introduction of the second gene pool in the Bekaa region followed an evolution towards more extensive clonal propagation of 'Halwani' limiting hybridizations. Furthermore, some pairs of geographically distant 'Halwani' orchards, exhibited low genetic distances, suggesting that a network of exchanges between farmers was effective on a large scale and/or that farmers brought clonal plant material from a common source. CONCLUSIONS: Almond diversification in Lebanon is clearly related to the evolution of propagation practices adapted to self-incompatible cultivars. The comparison between both cultivars demonstrated the genetic effects of the introduction of a new cultivar and the associated grafting propagation practices. Our study provided information to develop a strategy for in situ conservation of cultivars and to limit gene flow from introduced material to ancient orchards.

Add-on peg-interferon leads to loss of HBsAg in patients with HBeAg-negative chronic hepatitis and HBV DNA fully suppressed by long-term nucleotide analogs.

BACKGROUND AND OBJECTIVE: The aim of this study was to prospectively evaluate whether the addition of peg-IFN to a stable NA regimen leads to loss of HBsAg in HBeAg-negative patients with chronic hepatitis and HBV DNA fully suppressed by long-term NA treatment. STUDY DESIGN: We analyzed HBsAg levels in 10 HBsAg-positive, HBeAg-negative patients who received peg-IFN alpha-2a in addition to a NA regimen. Treatment lasted a maximum of 96 weeks, according to changes in the HBsAg titer. Before peg-IFN therapy, HBV DNA levels had been below the limit of detection for at least three years. RESULTS: HBsAg levels declined in nine patients. Among these nine, four became HBsAg-negative after 48 weeks of peg-IFN treatment; these patients received peg-IFN for only 48 weeks. NAs were stopped in these four patients, and these levels remained stable for at least 18 months (loss of HBsAg; HBV-DNA negative). HBs seroconversion was observed in two patients. The remaining five patients received 96 weeks of peg-IFN therapy. One patient became HBsAg-negative at the end of peg-IFN therapy; another became HBsAg-negative six months later. Three patients did not become HBsAg-negative. NAs were stopped in the two patients who became HBsAg-negative with no relapse during 12 months of follow up. CONCLUSIONS: In HBsAg-positive, HBeAg-negative patients with HBV DNA were fully suppressed by long-term NA treatment, the addition of peg-INF for a maximum of 96 weeks based on HBsAg-titer monitoring led to a loss of HBsAg and cessation of NA therapy in six out of ten patients, with no relapse for 12-18 months of follow up. HBs seroconversion was observed in two patients.

Gene flow among wild and domesticated almond species: insights from chloroplast and nuclear markers.

Hybridization has played a central role in the evolutionary history of domesticated plants. Notably, several breeding programs relying on gene introgression from the wild compartment have been performed in fruit tree species within the genus Prunus but few studies investigated spontaneous gene flow among wild and domesticated Prunus species. Consequently, a comprehensive understanding of genetic relationships and levels of gene flow between domesticated and wild Prunus species is needed. Combining nuclear and chloroplastic microsatellites, we investigated the gene flow and hybridization among two key almond tree species, the cultivated Prunus dulcis and one of the most widespread wild relative Prunus orientalis in the Fertile Crescent. We detected high genetic diversity levels in both species along with substantial and symmetric gene flow between the domesticated P. dulcis and the wild P. orientalis. These results were discussed in light of the cultivated species diversity, by outlining the frequent spontaneous genetic contributions of wild species to the domesticated compartment. In addition, crop-to-wild gene flow suggests that ad hoc transgene containment strategies would be required if genetically modified cultivars were introduced in the northwestern Mediterranean.

Polymorphic microsatellite loci from Dacryodes edulis (Burseraceae), a Central African rainforest and fruit-tree species.

PREMISE OF THE STUDY: Microsatellite markers were isolated and characterized from Dacryodes edulis (Burseraceae), a tropical rainforests fruit tree of central Africa. METHODS AND RESULTS: Using an enrichment protocol, six microsatellites loci were developed from Dacryodes edulis. We investigated polymorphism using 45 trees from three widely separated populations in Cameroon. All loci were polymorphic, with the number of alleles ranging from 2 to 15. Polymorphism was widely variable among loci and expected heterozygosities ranged from 0.06 to 0.84 with a mean value of 0.49. CONCLUSIONS: These loci will be useful for the in-depth analysis of population structure and phylogeographic variation throughout the distribution range of Dacryodes edulis and other related taxa, Dacryodes buettneri and D. normandii, in which all loci were also amplified. Furthermore, they will offer the opportunity to study early domestication processes acting on the genetic diversity of Dacryodes edulis.

Characterization of the interaction between liposomal formulations and Pseudomonas aeruginosa.

The interactions between three liposomal formulations and Pseudomonas aeruginosa cells were evaluated by a lipid mixing assay and electron paramagnetic resonance (EPR) spectroscopy. The effect of the bacteria on the liposomal phase characteristics, the release of the liposomes' content, and the uptake rate of gentamicin by bacteria were monitored as a function of time, using EPR spectroscopy. The [16-DSA uptake](Total) from DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) liposomes reached 93 +/- 12% over a 3-hour assay period, of which 9% crossed the bacterial inner membrane. A small amount of 16-DSA uptake from DPPC/Chol (cholesterol) vesicles was found throughout the 3-hour period of time. Although DPPC/DMPG (dimyristoylphosphatidylglycerol) vesicles showed a smaller value of [16-DSA uptake](Total) with respect to that of DPPC vesicles, they appeared to be effective in disrupting the bacterial membrane, resulting in a greater accumulation of 16-DSA inside the inner membrane. Exposure to bacteria caused the DPPC/Chol, DPPC, and DPPC/DMPG formulations to release 4.6 +/- 1.5, 17.6 +/- 1.2, and 34 +/- 3.7% of their content, respectively. Time-dependent fluid regions were developed within the vesicles when mixed with bacteria, and their growth over time depended on liposomal formulations. Incubation of gentamicin with bacteria for 3 hours resulted in 87 +/- 3% of the drug crossing the bacterial inner membrane. In conclusion, interaction between the liposome drug carriers and the bacterial cells result in vesicle fusion, disruption of the bacterial membrane, release of the liposomal content in the close vicinity of the bacteria cells, and the subsequent intracellular uptake of the released liposomal content.

The effect of aminoglycoside antibiotics on the thermodynamic properties of liposomal vesicles.

Liposomes are ideal drug-delivery systems because they can alter the pharmacokinetic characteristics and biodistribution profile of the incorporated bioactive molecule. The effect of the aminoglycoside antibiotics, gentamicin (GN), tobramycin (TOB), and amikacin (AMI), on the thermodynamic properties of multilamellar vesicles composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was studied by using differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR), and (31)P nuclear magnetic resonance (NMR) spectroscopy. The relationship between the structure of aminoglycoside antibiotics and their effect on the physical properties of the liposomal bilayers was investigated. The incorporation of the drugs was achieved and an osmotic gradient created by controlling the mole ratio of the drug inside to that outside of the DPPC vesicles so that [drug(inside DPPC)]/[drug(outside DPPC)] was 1:0, 1:0.2, 1:1, or 1:2.5. Incorporation of the drugs into liposomes caused the T(m) to shift to a higher temperature and the delta H(m) and delta T(1/2) values to decrease. The 2A(max) and the order parameter (S), obtained from the EPR spectra, indicated that the fluidity of the liposomal membrane was affected by the type of drug and by the concentration used; GN and TOB decreased the fluidity and disturbed chain packing at mole ratios of [drug(inside DPPC)]/[drug(outside DPPC)] ranging from 1:0 to 1:0.2, while AMI increased the fluidity and disrupted chain packing at an osmotic gradient of 1:2.5. In conclusion, the molecular organization and thermotropic properties of the multilamellar DPPC vesicles were dependent on the osmotic gradient and structure of the aminoglycoside.

A weed-crop complex in sorghum: The dynamics of genetic diversity in a traditional farming system.

Despite the major ecological and economic impacts of gene flow between domesticated plants and their wild relatives, many aspects of the process, particularly the relative roles of natural and human selection in facilitating or constraining gene flow, are still poorly understood. We developed a multidisciplinary approach, involving both biologists and social scientists, to investigate the dynamics of genetic diversity of a sorghum weed-crop complex in a village of Duupa farmers in northern Cameroon. Farmers distinguish a gradient from weedy morphotypes (naa baa see, haariya, and genkiya) to domesticated morphotypes; haariya and genkiya have intermediate morphological traits. We investigated the pattern of diversity in this complex using both morphological and genetic data. Our biological results are interpreted in the light of data on farmers' taxonomy and practices such as spatial pattern of planting and plant selection. Both morphological and genetic data are congruent with farmers' taxonomy and confirm the introgressed status of intermediate weedy morphotypes. Farmers actively select against weedy morphotypes, but several practices unconsciously favor gene flow. Furthermore, haariya and genkiya may facilitate introgression between naa baa see and domesticated morphotypes by virtue of their intermediate flowering period and their mode of management by farmers.

Comparison of INR stability between self-monitoring and standard laboratory method: preliminary results of a prospective study in 67 mechanical heart valve patients.

INTRODUCTION: Thromboembolic accidents and haemorrhage are the main complications observed during long-term follow-up of mechanical heart valve patients. Several suggestions for improving anticoagulation quality have been made, including international normalised ratio (INR) self-monitoring. OBJECTIVES: We report the preliminary results of a single-centre, open, randomised study (scheduled population of 200 patients), which compares monthly laboratory monitoring (group A) versus weekly self-monitoring of INR (group B). The primary aim is INR stability improvement within the target range, and the secondary aim is adverse events reduction. PATIENTS AND METHODS: Between May 2004 and June 2005, 67 patients with an average age of 56.6 years (+/-9.6), were enrolled in the study (group A: 34 patients, group B: 33 patients). The mean follow-up was 47 weeks (+/-11.5). The two groups differed only in the sex ratio (44.1 and 21.2% of women in groups A and B respectively, p=0.0459). Mechanical heart valves were aortic in 73% of patients, mitral in 13.5%, and multiple in 13.5%. Sixty-five patients (97%) were treated with fluindione, the others with acenocoumarol. The intraclass correlation coefficient between the self- and laboratory-monitored INR was 0.75. RESULTS: The time spent in the INR target range (group A: 53+/-19%, group B: 57+/--19%, p=0.45) and the time spent in the INR therapeutic range, between 2 and 4.5, (group A: 86+/-14%, group B: 91+/-7%, p=0.07) are longer in group B, but not significantly so. For patients outside the range, the absolute mean deviation of INR from the target or therapeutic range (range standardized between 0 and 100) is lower for the self-monitoring group (41.1+/-39.3 and 11.27+/-11.2) than for the control group (62.4+/-72.6 and 39.2+/-52.8). This difference is significant (p=0.0004 and p=0.0005). Eighteen adverse events were reported: 17 haemorrhages, 13 in group A (9 mild, 4 serious) and four in group B (all mild), and one sudden death in group B, two days after the patient's discharge. No thromboembolic events were reported. Six patients (8.8 %), 3 in each group, dropped out of the study. CONCLUSION: This first study evaluating INR self-monitoring in France shows that this method leads to better stability of the INR within the target range. On the basis of these preliminary data, this appears to be related to a decrease in serious haemorrhages (11.8% serious haemorrhage cases in group A versus 0% in group B, p=0.06, NS).

Liposomes as a carrier for gentamicin delivery: development and evaluation of the physicochemical properties.

The physicochemical properties of liposomal formulations containing gentamicin were investigated. A sustained release of gentamicin from liposomes was observed at both 4 degrees C and 37 degrees C in phosphate buffered saline. The distribution of the mean diameters of these liposomal formulations, evaluated by dynamic light scattering (DLS) over a 48h time period, was bimodal with large polydispersity index values, i.e., > or =0.6. Incorporation of 5- or 16-doxylstearic acids (5- or 16-DSL) into the liposomes allowed the use of EPR spectroscopy to study the fluidity, order parameter, and phase behavior of the phospholipid bilayers in response to the compositions, temperature and time. While, our results revealed that gentamicin disturbs the packing and fluidizes the phospholipid chains, it did not seem to alter the nature of the microdomains at the polar interface of the bilayers. Simulation of the EPR spectra of 5-DSL containing liposomes revealed (1) the heterogeneous nature of the liposomal domains at the polar interfacial region, and (2) that encapsulation of gentamicin neither significantly alters the dynamic properties of the existing domains, nor induces the phase repartition of the liposomes within a 48h time course.

Local genetic diversity of sorghum in a village in northern Cameroon: structure and dynamics of landraces.

We present the first study of patterns of genetic diversity of sorghum landraces at the local scale. Understanding landrace diversity aids in deciphering evolutionary forces under domestication, and has applications in the conservation of genetic resources and their use in breeding programs. Duupa farmers in a village in Northern Cameroon distinguished 59 named sorghum taxa, representing 46 landraces. In each field, seeds are sown as a mixture of landraces (mean of 12 landraces per field), giving the potential for extensive gene flow. What level of genetic diversity underlies the great morphological diversity observed among landraces? Given the potential for gene flow, how well defined genetically is each landrace? To answer these questions, we recorded spatial patterns of planting and farmers' perceptions of landraces, and characterized 21 landraces using SSR markers. Analysis using distance and clustering methods grouped the 21 landraces studied into four clusters. These clusters correspond to functionally and ecologically distinct groups of landraces. Within-landrace genetic variation accounted for 30% of total variation. The average F(is) over landraces was 0.68, suggesting high inbreeding within landraces. Differentiation among landraces was substantial and significant (F(st) = 0.36). Historical factors, variation in breeding systems, and farmers' practices all affected patterns of genetic variation. Farmers' practices are key to the maintenance, despite gene flow, of landraces with different combinations of agronomically and ecologically pertinent traits. They must be taken into account in strategies of conservation and use of genetic resources.

Kinetics of hepatitis C virus RNA load during pegylated interferon alpha-2a and ribavirin treatment in naïve genotype 1 patients.

BACKGROUND: Pegylated interferon given for 24 or 48 weeks constitutes the most effective initial therapy for the treatment of chronic hepatitis C. It has been shown that viral load at week 2 appears the best time for predicting response to treatment. The objectives of this study were to assess whether the hepatitis C virus (HCV) RNA viral decline is predictive of sustained virological response (SVR) and to determine the best time for predicting complete response in our cohort of naïve patients treated with pegylated interferon alpha-2a (Peg-IFN alpha-2a) and ribavirin. RESULTS: Twenty patients treated with Peg-IFN alpha-2a and ribavirin for 48 weeks were studied. Six months after the end of treatment, a SVR (negative HCV RNA measured by PCR six months after the end of therapy) was obtained in 9 patients. Samples were obtained before and at week 2, 4, 8, and 12. At the end of week 2, viral load decreased more than 1.39 log in 8 out of the 9 patients with SVR and in 1 out of the 11 other patients. When we considered the viral load reduction from baseline to each week of treatment, week 2 appeared to be the best point time for predicting SVR, with a sensitivity of 91% (95%CI: 59;99), a specificity of 89% (52;98), a positive predictive value of 91% (59;99) and a negative predictive value of 89% (57;98). CONCLUSION: During treatment with Peg-IFN alpha-2a plus ribavirin in genotype 1 patients, when the main objective of the treatment is viral eradication, viral kinetics showed that week 2 appeared to be the best time point for predicting SVR. Our results must be further confirmed on a larger cohort.

Hepatitis C virus RNA load in relapsed patients: week two of treatment is the best time to predict the complete response.

OBJECTIVE: An early virological response has been shown to be predictive of a sustained virological response to antiviral treatment in chronic hepatitis C infection. The aim of the study was to analyse viral kinetics during the first 6 weeks of treatment (interferon plus ribavirin) in 18 relapsed hepatitis C patients after a first course of interferon monotherapy. METHODS: We studied 18 relapsed patients treated with interferon and ribavirin. A sustained virological response (negative HCV RNA measured by polymerase chain reaction 6 months after the end of therapy) was obtained in 12 patients. Samples were obtained before therapy and each week for 6 weeks during therapy; HCV RNA levels were determined using quantitative bDNA. RESULTS: At the end of week two, a viral-load drop of more than 2.20 log was observed in all the 12 patients with a sustained virological response and in none of the six other patients. When we considered the median of the viral load reduction from baseline for each week of treatment, week two appeared to be the time point most predictive of a sustained viral response (positive predictive value 83%; negative predictive value 92%). CONCLUSION: During treatment with interferon plus ribavirin in relapsed hepatitis C patients, viral kinetics showed that the second week of treatment appeared to be the time point most predictive of a sustained viral response.

[Modalities of care in anti HCV positive patients identified in General Medicine in the Alpes-Maritimes district]. / Analyse de la prise en charge en Médecine Générale de malades identifiés comme positifs pour le virus de l'hépatite C dans le département des Alpes-Maritimes.

UNLABELLED: Little is known about the management of HCV infected patients after screening in general medicine. On May 2000, 75 General Practitioners (GP) from South Eastern France were involved in an HCV screening campaign. Fifteen per cent of 6321 patients seen during this period presented at least one of the following risk factors: blood transfusion before 1991, drug abuse, imprisonment. Among the 238 HCV positive patients, 9 new cases were reported. AIM OF THE STUDY: To describe the management of these patients. RESULTS: One hundred and fifty-nine of these 238 cases were studied (100 males and 59 females). Mean age was 42 +/- 12 years. Mean delay between contamination and the discovery of HCV positive status was 8 +/- 6 years. Main routes of infection were: drug abuse (78%), transfusion before 1991 (15%), imprisonment (7%). The GP performed the entire follow up of cases in 34%. The following investigations were performed: ALT dosage in 98% (elevated: 59%, normal: 41%), qualitative HCV RNA detection in 77% (positive 78%, negative 22%), quantitative HCV RNA detection in 27%. A liver biopsy was performed in 62 patients (39%). Among the 159 patients 39 (19%) were treated with Interferon (with or without Ribavirin). Treatment and liver biopsy were not performed for the following reasons: patient refusal (26%), normal ALT values (26%), HIV co-infection (27%), elderly patients (3%), decompensated cirrhosis (5%), drug abuse or excessive alcohol intake (12%). CONCLUSION: The main reasons that adequate management in hepatitis C patients failed was fear of liver biopsy and/or Interferon therapy, and a population difficult that was difficult to treat (HIV coinfected, drug abuse or chronic alcoholism), A better collaboration between general practitioners and specialists could help improve the management of these patients.

Tracking a genetic signal of extinction-recolonization events in a neotropical tree species: Vouacapoua americana Aublet in French Guiana.

Drier periods from the late Pleistocene and early Holocene have been hypothesized to have caused the disappearance of various rainforest species over large geographical areas in South America and restricted the extant populations to mesic sites. Subsequent improvement in climatic conditions has been associated with recolonization. Changes in population size associated with these extinction-recolonization events should have affected genetic diversity within species. However, these historical hypotheses and their genetic consequences have rarely been tested in South America. Here, we examine the diversity of the chloroplast and nuclear genomes in a Neotropical rainforest tree species, Vouacapoua americana (Leguminosae, Caesalpinioideae) in French Guiana. The chloroplast diversity was analyzed using a polymerase chain reaction-restriction fragment length polymorphism method (six pairs of primers) in 29 populations distributed over most of French Guiana, and a subset of 17 populations was also analyzed at nine polymorphic microsatellite loci. To determine whether this species has experienced extinction-recolonization, we sampled populations in areas supposedly not or only slightly affected by climatic changes, where the populations would not have experienced frequent extinction, and in areas that appear to have been recently recolonized. In the putatively recolonized areas, we found patches of several thousands of hectares homogeneous for chloroplast variation that can be interpreted as the effect of recolonization processes from several geographical origins. In addition, we observed that, for both chloroplast and nuclear genomes, the populations in newly recolonized areas exhibited a significantly smaller allelic richness than others. Controlling for geographic distance, we also detected a significant correlation between chloroplast and nuclear population differentiation. This result indicates a cytonuclear disequilibrium that can be interpreted as a historical signal of a genetic divergence between fragmented populations. In conclusion, the spatial genetic structure of contemporary V. americana populations shows evidence that this species has experienced large extinction-recolonization events, which were possibly caused by past climatic change.