Choosing a random distribution with prescribed risks

We describe several simulation algorithms that yield random probability distributions with given values of risk measures. In case of vanilla risk measures, the algorithms involve combining and transforming random cumulative distribution functions or random Lorenz curves obtained by simulating rather general random probability distributions on the unit interval. A new algorithm based on the simulation of a weighted barycentres array is suggested to generate random probability distributions with a given value of the spectral risk measure.

Predicting the distribution of forest tree species using topographic variables and vegetation index in eastern Acre, Brazil

Species distribution modeling has relevant implications for the studies of biodiversity, decision making about conservation and knowledge about ecological requirements of the species. The aim of this study was to evaluate if the use of forest inventories can improve the estimation of occurrence probability, identify the limits of the potential distribution and habitat preference of a group of timber tree species. The environmental predictor variables were: elevation, slope, aspect, normalized difference vegetation index (NDVI) and height above the nearest drainage (HAND). To estimate the distribution of species we used the maximum entropy method (Maxent). In comparison with a random distribution, using topographic variables and vegetation index as features, the Maxent method predicted with an average accuracy of 86% the geographical distribution of studied species. The altitude and NDVI were the most important variables. There were limitations to the interpolation of the models for non-sampled locations and that are outside of the elevation gradient associated with the occurrence data in approximately 7% of the basin area. Ceiba pentandra (samaúma), Castilla ulei (caucho) and Hura crepitans (assacu) is more likely to occur in nearby water course areas. Clarisia racemosa (guariúba), Amburana acreana (cerejeira), Aspidosperma macrocarpon (pereiro), Apuleia leiocarpa (cumaru cetim), Aspidosperma parvifolium (amarelão) and Astronium lecointei (aroeira) can also occur in upland forest and well drained soils. This modeling approach has potential for application on other tropical species still less studied, especially those that are under pressure from logging.

Analysis and Simulation of Transverse Random Fracture of Long Fibre Reinforced Composites

La present tesi proposa una metodología per a la simulació probabilística de la fallada de la matriu en materials compòsits reforçats amb fibres de carboni, basant-se en l'anàlisi de la distribució aleatòria de les fibres. En els primers capítols es revisa l'estat de l'art sobre modelització matemàtica de materials aleatoris, càlcul de propietats efectives i criteris de fallada transversal en materials compòsits. El primer pas en la metodologia proposada és la definició de la determinació del tamany mínim d'un Element de Volum Representatiu Estadístic (SRVE) . Aquesta determinació es du a terme analitzant el volum de fibra, les propietats elàstiques efectives, la condició de Hill, els estadístics de les components de tensió i defromació, la funció de densitat de probabilitat i les funcions estadístiques de distància entre fibres de models d'elements de la microestructura, de diferent tamany. Un cop s'ha determinat aquest tamany mínim, es comparen un model periòdic i un model aleatori, per constatar la magnitud de les diferències que s'hi observen. Es defineix, també, una metodologia per a l'anàlisi estadístic de la distribució de la fibra en el compòsit, a partir d'imatges digitals de la secció transversal. Aquest anàlisi s'aplica a quatre materials diferents. Finalment, es proposa un mètode computacional de dues escales per a simular la fallada transversal de làmines unidireccionals, que permet obtenir funcions de densitat de probabilitat per a les variables mecàniques. Es descriuen algunes aplicacions i possibilitats d'aquest mètode i es comparen els resultats obtinguts de la simulació amb valors experimentals.

Effect of sequence distribution on the morphology, crystallization, melting, and biodegradation of poly(epsilon-caprolactone-co-epsilon-caprolactam) copolymers

Two types of poly(epsilon-caprolactone (CLo)-co-poly(epsilon-caprolactam (CLa)) copolymers were prepared by catalyzed hydrolytic ring-opening polymerization. Both cyclic comonomers were added simultaneously in the reaction medium for the First type or materials where copolymers have a random distribution of counits, as evidenced by H-1 and C-13 NMR. For the second type of copolymers, the cyclic comonomers were added sequentially, yielding diblock poly(ester-amides). The materials were characterized by differential scanning calorimetry (DSC), wide- and small-angle X-ray scattering (WAXS and SAXS), and transmission and scanning electron microscopies (TEM and SEM). Their biodegradation in compost was also studied. All copolymers were found to be miscible by the absence of structure in the melt. TEM revealed that all samples exhibited a crystalline lamellar morphology. DSC and WAXS showed that in a wide composition range (CLo contents from 6 to 55%) only the CLa units were capable of crystallization in the random copolymers. The block copolymer samples only experience a small reduction of crystallization and melting temperature with composition, and this was attributed to a dilution effect caused by the miscible noncrystalline CLo units. The comparison between block and random copolymers provided a unique opportunity to distinguish the dilution effect of the CLo units on the crystallization and melting of the polyamide phase from the chemical composition effect in the random copolymers case, where the CLa sequences are interrupted statistically by the CLo units, making the crystallization of the polyamide strongly composition dependent. Finally, the enzymatic degradation of the copolymers in composted soil indicate a synergistic behavior where much faster degradation was obtained for random copolymers witha CLo content larger than 30% than for neat PCL.

Statnote 37 : the negative binomial distribution

An organism living in water, and present at low density, may be distributed at random and therefore, samples taken from the water are likely to be distributed according to the Poisson distribution. The distribution of many organisms, however, is not random, individuals being either aggregated into clusters or more uniformly distributed. By fitting a Poisson distribution to data, it is only possible to test the hypothesis that an observed set of frequencies does not deviate significantly from an expected random pattern. Significant deviations from random, either as a result of increasing uniformity or aggregation, may be recognized by either rejection of the random hypothesis or by examining the variance/mean (V/M) ratio of the data. Hence, a V/M ratio not significantly different from unity indicates a random distribution, greater than unity a clustered distribution, and less then unity a regular or uniform distribution . If individual cells are clustered, however, the negative binomial distribution should provide a better description of the data. In addition, a parameter of this distribution, viz., the binomial exponent (k), may be used as a measure of the ‘intensity’ of aggregation present. Hence, this Statnote describes how to fit the negative binomial distribution to counts of a microorganism in samples taken from a freshwater environment.

Répteis da Estação Ecológica Serra Geral do Tocantins, Brasil Central

Os Cerrados sul-americanos abrigam alta diversidade de répteis, incluindo elevado número de endemismos. No entanto, o conhecimento desta diversidade é ainda incompleto frente à acelerada transformação das paisagens naturais no Brasil central. Constituem, portanto, uma das regiões prioritárias para estudo e conservação da biodiversidade mundial. Estudos intensivos sobre a fauna de répteis do Cerrado são necessários e urgentes para melhor compreensão dos processos que levaram à sua origem e distribuição e para subsidiar ações de conservação. Por meio de métodos padronizados, amostramos duas regiões ainda inexploradas da Estação Ecológica Serra Geral do Tocantins, situada na região do Jalapão. Registramos 45 espécies de répteis para a EESGT e entorno, o que representa uma riqueza alta e comparável à de outras regiões bem amostradas do Cerrado. Curvas de acumulação e estimadores indicam que a riqueza local de lagartos e anfisbenídeos aproxima-se da riqueza real enquanto a de serpentes é subestimada. A distribuição não-aleatória das espécies na paisagem concorda com evidências anteriores sugerindo utilização diferencial dos hábitats pelos répteis. Reunindo os resultados do presente estudo com os de levantamentos prévios realizados na região, registramos 88 espécies de répteis para o Jalapão sendo oito registros novos que incluem Bachia oxyrhina uma espécie recém descrita da região. As espécies da área apresentam três padrões gerais de distribuição: (1) espécies endêmicas do Cerrado, (2) espécies compartilhadas com domínios da diagonal de formações abertas sul-americanas, e (3) espécies de ampla ocorrência, compartilhadas também com ecossistemas florestais. Prevalecem espécies de ampla distribuição, porém é grande o número de espécies típicas do Cerrado, incluindo cinco possivelmente endêmicas do Jalapão, e há contribuição importante da fauna da Caatinga. A distribuição dos répteis em escala local e regional demonstra a necessidade de considerar a heterogeneidade paisagística para o planejamento de diretrizes visando à conservação em regiões do Cerrado. Por sua grande extensão, posição biogeográfica e complexidade de relevo e tipos de hábitat, a EESGT tem papel fundamental para a preservação e conhecimento da diversidade de répteis do Cerrado.

Elastic Fibers in Reinke`s Edema

Objectives: We describe the distribution of elastic system fibers in the superficial layer of the lamina propria of Reinke`s edema, as compared with normal vocal folds. Methods: Weigert`s resorcin-fuchsin stain after oxidation with 10% oxone was used to study the arrangement of elastic fibers. The findings were categorized and afterward compared with the severity of Reinke`s edema. Results: Analysis of 20 specimens of vocal folds with Reinke`s edema showed that the network of thin elastic fibers in Reinke`s space lost their undulated appearance and had a tangled aspect. In addition, these fibers were no longer parallel to the epithelial basement membrane, but had a random distribution scattered throughout Reinke`s space. The elastic fiber network immediately below the epithelial basement membrane also appeared more fragmented in Reinke`s edema because of some alteration in organization combined with the 5-mu m-thick histologic sectioning plane. No significant difference in the degree of elastic system fiber disarrangement was observed between severity grades II and III (p = 0.382). Large areas of disarrangement were predominant (80% of cases). Conclusions: The disarrangement of elastic fibers in Reinke`s edema may cause insufficient tissue resistance and resilience, contributing to the hypermobility observed in Reinke`s edema.

Density functional theory analysis of the influence of pore wall heterogeneity on adsorption in carbons

Density functional theory for adsorption in carbons is adapted here to incorporate a random distribution of pore wall thickness in the solid, and it is shown that the mean pore wall thickness is intimately related to the pore size distribution characteristics. For typical carbons the pore walls are estimated to comprise only about two graphene layers, and application of the modified density functional theory approach shows that the commonly used assumption of infinitely thick walls can severely affect the results for adsorption in small pores under both supercritical and subcritical conditions. Under supercritical conditions the Henry's law coefficient is overpredicted by as much as a factor of 2, while under subcritical conditions pore wall heterogeneity appears to modify transitions in small pores into a sequence of smaller ones corresponding to pores with different wall thicknesses. The results suggest the need to improve current pore size distrubution analysis methods to allow for pore wall heterogeneity. The density functional theory is further extended here to allow for interpore adsorbate interactions, and it appears that these interaction are negligible for small molecules such as nitrogen but significant for more strongly interacting heavier molecules such as butane, for which the traditional independent pore model may not be adequate.

The multipoint Morisita index for the analysis of spatial patterns

In many fields, the spatial clustering of sampled data points has many consequences. Therefore, several indices have been proposed to assess the level of clustering affecting datasets (e.g. the Morisita index, Ripley's Kfunction and Rényi's generalized entropy). The classical Morisita index measures how many times it is more likely to select two measurement points from the same quadrats (the data set is covered by a regular grid of changing size) than it would be in the case of a random distribution generated from a Poisson process. The multipoint version (k-Morisita) takes into account k points with k >= 2. The present research deals with a new development of the k-Morisita index for (1) monitoring network characterization and for (2) detection of patterns in monitored phenomena. From a theoretical perspective, a connection between the k-Morisita index and multifractality has also been found and highlighted on a mathematical multifractal set.

Segregation in a mycorrhizal fungus alters rice growth and symbiosis-specific gene transcription

Arbuscular mycorrhizal fungi (AMF) form symbioses with the majority of plants, improving plant nutrition and diversity. Evidence exists suggesting that AMF contain populations of genetically different nucleotypes coexisting in a common cytoplasm. This potentially has two important consequences for their genetics. First, by random distribution of nuclei at spore formation, new offspring of an AMF could receive different complements of nucleotypes compared to the parent or siblings-we consider this as segregation. Second, genetic exchange between AMF would allow the mixing of nuclei, altering nucleotype diversity in new spores. Because segregation was assumed not to occur and genetic exchange has only recently been demonstrated, no attempts have been made to test whether this affects the symbiosis with plants. Here, we show that segregation occurs in the AMF Glomus intraradices and can enhance the growth of rice up to five times, even though neither parental nor crossed AMF lines induced a positive growth response. This process also resulted in an alteration of symbiosis-specific gene transcription in rice. Our results demonstrate that manipulation of AMF genetics has important consequences for the symbiotic effects on plants and could be used to enhance the growth of globally important crops.

Broken noses for the gods: ritual battles in the Atacama Desert during the Tiwanaku period

The sample consists of 226 skulls from the Atacameño cemetery of Coyo Oriente (639-910 AD), associated with the Tiwanaku period. The authors analyzed signs of acute trauma typically associated with violence, and the results were 12% of men and 9.9% of women displaying any type of lesion related to violence. In males, concentration of these non-lethal lesions in the nasal region (10.4%) as opposed to a random distribution over the entire skull (1.6%), suggests that the blows were struck during rituals. The cultural context of this period, with a strong ideological influence from Tiwanaku, supports the ritual hypothesis, since both the ethnographic as well as archeological records point to the existence of non-lethal violent bleeding with ritual beating to the face. Such rituals persist to this day among certain Andean populations. Among women, the most plausible hypothesis for the lesions (3.9% in the skull, 4.9% in the nasal bones, and 0.9% in the face) is domestic conflicts, since they show a random distribution. Previous studies with other Atacameño samples had indicated the same results for women.

Genetic studies of the Roma (Gypsies): a review

Background: Data provided by the social sciences as well as genetic research suggest that the 8-10 million Roma (Gypsies) who live in Europe today are best described as a conglomerate of genetically isolated founder populations. The relationship between the traditional social structure observed by the Roma, where the Group is the primary unit, and the boundaries, demographic history and biological relatedness of the diverse founder populations appears complex and has not been addressed by population genetic studies. Results: Recent medical genetic research has identified a number of novel, or previously known but rare conditions, caused by private founder mutations. A summary of the findings, provided in this review, should assist diagnosis and counselling in affected families, and promote future collaborative research. The available incomplete epidemiological data suggest a non-random distribution of disease-causing mutations among Romani groups.Conclusion: Although far from systematic, the published information indicates that medical genetics has an important role to play in improving the health of this underprivileged and forgotten people of Europe. Reported carrier rates for some Mendelian disorders are in the range of 5 -15%, sufficient to justify newborn screening and early treatment, or community-based education and carrier testing programs for disorders where no therapy is currently available. To be most productive, future studies of the epidemiology of single gene disorders should take social organisation and cultural anthropology into consideration, thus allowing the targeting of public health programs and contributing to the understanding of population structure and demographic history of the Roma.

Les coûts des dommages éléments naturels aux bâtiments et l'influence des facteurs du risque dans un contexte d'assurance immobilière : analyse de cas des innondations et de la grêle en Suisse

In Switzerland, the annual cost of damage by natural elements has been increasing for several years despite the introduction of protective measures. Mainly induced by material destruction building insurance companies have to pay the majority of this cost. In many European countries, governments and insurance companies consider prevention strategies to reduce vulnerability. In Switzerland, since 2004, the cost of damage due to natural hazards has surpassed the cost of damage due to fire; a traditional activity of the Cantonal Insurance company (EGA). Therefore, the strategy for efficient fire prevention incorporates a reduction of the vulnerability of buildings. The thesis seeks to illustrate the relevance of such an approach when applied to the damage caused by natural hazards. It examines the role of insurance place and its involvement in targeted prevention of natural disasters. Integrated risk management involves a faultless comprehension of all risk parameters The first part of the thesis is devoted to the theoretical development of the key concepts that influence risk management, such as: hazard, vulnerability, exposure or damage. The literature on this subject, very prolific in recent years, was taken into account and put in perspective in the context of this study. Among the risk parameters, it is shown in the thesis that vulnerability is a factor that we can influence efficiently in order to limit the cost of damage to buildings. This is confirmed through the development of an analysis method. This method has led to the development of a tool to assess damage to buildings by flooding. The tool, designed for the property insurer or owner, proposes several steps, namely: - Vulnerability and damage potential assessment; - Proposals for remedial measures and risk reduction from an analysis of the costs of a potential flood; - Adaptation of a global strategy in high-risk areas based on the elements at risk. The final part of the thesis is devoted to the study of a hail event in order to provide a better understanding of damage to buildings. For this, two samples from the available claims data were selected and analysed in the study. The results allow the identification of new trends A second objective of the study was to develop a hail model based on the available data The model simulates a random distribution of intensities and coupled with a risk model, proposes a simulation of damage costs for the determined study area. Le coût annuel des dommages provoqués par les éléments naturels en Suisse est conséquent et sa tendance est en augmentation depuis plusieurs années, malgré la mise en place d'ouvrages de protection et la mise en oeuvre de moyens importants. Majoritairement induit par des dégâts matériels, le coût est supporté en partie par les assurances immobilières en ce qui concerne les dommages aux bâtiments. Dans de nombreux pays européens, les gouvernements et les compagnies d'assurance se sont mis à concevoir leur stratégie de prévention en termes de réduction de la vulnérabilité. Depuis 2004, en Suisse, ce coût a dépassé celui des dommages dus à l'incendie, activité traditionnelle des établissements cantonaux d'assurance (ECA). Ce fait, aux implications stratégiques nombreuses dans le domaine public de la gestion des risques, résulte en particulier d'une politique de prévention des incendies menée efficacement depuis plusieurs années, notamment par le biais de la diminution de la vulnérabilité des bâtiments. La thèse, par la mise en valeur de données actuarielles ainsi que par le développement d'outils d'analyse, cherche à illustrer la pertinence d'une telle approche appliquée aux dommages induits par les phénomènes naturels. Elle s'interroge sur la place de l'assurance et son implication dans une prévention ciblée des catastrophes naturelles. La gestion intégrale des risques passe par une juste maîtrise de ses paramètres et de leur compréhension. La première partie de la thèse est ainsi consacrée au développement théorique des concepts clés ayant une influence sur la gestion des risques, comme l'aléa, la vulnérabilité, l'exposition ou le dommage. La littérature à ce sujet, très prolifique ces dernières années, a été repnse et mise en perspective dans le contexte de l'étude, à savoir l'assurance immobilière. Parmi les paramètres du risque, il est démontré dans la thèse que la vulnérabilité est un facteur sur lequel il est possible d'influer de manière efficace dans le but de limiter les coûts des dommages aux bâtiments. Ce raisonnement est confirmé dans un premier temps dans le cadre de l'élaboration d'une méthode d'analyse ayant débouché sur le développement d'un outil d'estimation des dommages aux bâtiments dus aux inondations. L'outil, destiné aux assurances immobilières, et le cas échéant aux propriétaires, offre plusieurs étapes, à savoir : - l'analyse de la vulnérabilité et le potentiel de dommages ; - des propositions de mesures de remédiation et de réduction du risque issues d'une analyse des coûts engendrés par une inondation potentielle; - l'adaptation d'une stratégie globale dans les zones à risque en fonction des éléments à risque. La dernière partie de la thèse est consacrée à l'étude d'un événement de grêle dans le but de fournir une meilleure compréhension des dommages aux bâtiments et de leur structure. Pour cela, deux échantillons ont été sélectionnés et analysés parmi les données de sinistres à disposition de l'étude. Les résultats obtenus, tant au niveau du portefeuille assuré que de l'analyse individuelle, permettent de dégager des tendances nouvelles. Un deuxième objectif de l'étude a consisté à élaborer une modélisation d'événements de grêle basée sur les données à disposition. Le modèle permet de simuler une distribution aléatoire des intensités et, couplé à un modèle d'estimation des risques, offre une simulation des coûts de dommages envisagés pour une zone d'étude déterminée. Les perspectives de ce travail permettent une meilleure focalisation du rôle de l'assurance et de ses besoins en matière de prévention.

Multiscale phylogeography: glacial history and autopolyploidy of Biscutella laevigata L. (Brassicaceae) in the Western Alps

Résumé Les changements climatiques du Quaternaire ont eu une influence majeure sur la distribution et l'évolution des biota septentrionaux. Les Alpes offrent un cadre spatio-temporel bien étudié pour comprendre la réactivité de la flore et le potentiel d'adaptation d'une espèce végétale face aux changements climatiques. Certaines hypothèses postulent une diversification des espèces en raison de la disparition complète de la flore des Alpes et d'un isolement important des espèces dans des refuges méridionaux durant les dernières glaciations (Tabula Rasa). Une autre hypothèse stipule le maintien de poches de résistance pour la végétation au coeur des Alpes (Nunataks). Comme de nombreuses espèces végétales présentant un grand succès écologique semblent avoir réagi aux glaciations par la multiplication de leur génome (autopolyploïdie), leur étude en milieu naturel devrait permettre de comprendre les avantages inhérents à la polyploïdie. Biscutella laevigata est un modèle emblématique de biogéographie historique, diverses études ayant montré que des populations diploïdes sont actuellement isolées dans les zones restées déglacées durant le dernier maximum glaciaire, alors que des tétraploïdes ont recolonisé l'ensemble des zones alpines mises à nu par le retrait des glaciers. Si le contexte périglaciaire semble avoir favorisé ce jeune complexe autopolyploïde, les circonstances et les avantages de cette mutation génomique ne sont pas encore clairs. Y a-t-il eu de multiples événements de polyploïdisation ? Dans quelle mesure affecte(nt)il(s) la diversité génétique et le potentiel évolutif des polyploïdes ? Les polyploïdes ont-ils une grande flexibilité génomique, favorisant une radiation adaptative, ou doivent-ils leur succès à une grande plasticité écologique ? Cette étude aborde ces questions à différentes échelles spatiales et temporelles. L'échelle régionale des Alpes occidentales permet d'aborder les facteurs distaux (aspects historiques), alors que l'échelle locale cherche à appréhender les facteurs proximaux (mécanismes évolutifs). Dans les Alpes occidentales, des populations ont été densément échantillonnées et étudiées grâce à (1) leur cytotype, (2) leur appartenance taxonomique, (3) leur habitat et (4) des marqueurs moléculaires de l'ADN chloroplastique, en vue d'établir leurs affinités évolutives. Á l'échelle locale, deux systèmes de population ont été étudiés : l'un où les populations persistent en périphérie de l'aire de distribution et l'autre au niveau du front actif de colonisation, en marge altitudinale. Les résultats à l'échelle des Alpes occidentales révèlent les sites d'intérêt (refuges glaciaires, principales barrières et voies de recolonisation) pour une espèce représentative des pelouses alpines, ainsi que pour la biodiversité régionale. Les Préalpes ont joué un rôle important dans le maintien de populations à proximité immédiate des Alpes centrales et dans l'évolution du taxon, voire de la végétation. Il est aussi démontré que l'époque glaciaire a favorisé l'autopolyploïdie polytopique et la recolonisation des Alpes occidentales par des lignées distinctes qui s'hybrident au centre des Alpes, influençant fortement leur diversité génétique et leur potentiel évolutif. L'analyse de populations locales en situations contrastées à l'aide de marqueurs AFLP montre qu'au sein d'une lignée présentant une grande expansion, la diversité génétique est façonnée par des forces évolutives différentes selon le contexte écologique et historique. Les populations persistant présentent une dispersion des gènes restreinte, engendrant une diversité génétique assez faible, mais semblent adaptées aux conditions locales de l'environnement. À l'inverse, les populations colonisant la marge altitudinale sont influencées par les effets de fondation conjugués à une importante dispersion des gènes et, si ces processus impliquent une grande diversité génétique, ils engendrent une répartition aléatoire des génotypes dans l'environnement. Les autopolyploïdes apparaissent ainsi comme capables de persister face aux changements climatiques grâce à certaines facultés d'adaptation locale et de grandes capacités à maintenir une importante diversité génétique lors de la recolonisation post-glaciaire. Summary The extreme climate changes of the Quaternary have had a major influence on species distribution and evolution. The European Alps offer a great framework to investigate flora reactivity and the adaptive potential of species under changing climate. Some hypotheses postulate diversification due to vegetation removal and important isolation in southern refugia (Tabula Rasa), while others explain phylogeographic patterns by the survival of species in favourable Nunataks within the Alps. Since numerous species have successfully reacted to past climate changes by genome multiplication (autopolyploidy), studies of such taxa in natural conditions is likely to explain the ecological success and the advantages of autopolyploidy. Early cytogeographical surveys of Biscutella laevigata have shed light on the links between autopolyploidy and glaciations by indicating that diploids are now spatially isolated in never-glaciated areas, while autotetraploids have recolonised the zones covered by glaciers- during the last glacial maximum. A periglacial context apparently favoured this young autopolyploid complex but the circumstances and the advantages of this genomic mutation remain unclear. What is the glacial history of the B. laevigata autopolyploid complex? Are there multiple events of polyploidisation? To what extent do they affect the genetic diversity and the evolutionary potential of polyploids? Is recolonisation associated with adaptive processes? How does long-term persistence affect genetic diversity? The present study addresses these questions at different spatiotemporal scales. A regional survey at the Western Alps-scale tackles distal factors (evolutionary history), while local-scale studies explore proximal factors (evolutionary mechanisms). In the Western Alps, populations have been densely sampled and studied from the (1) cytotypic, (2) morphotaxonomic, (3) habitat point of views, as well as (4) plastid DNA molecular markers, in order to infer their relationships and establish the maternal lineages phylogeography. At the local scale, populations persisting at the rear edge and populations recolonising the attitudinal margin at the leading edge have been studied by AFLPs to show how genetic diversity is shaped by different evolutionary forces across the species range. The results at the regional scale document the glacial history of a widespread species, representative of alpine meadows, in a regional area of main interest (glacial refugia, main barriers and recolonisation routes) and points out to sites of interest for regional biodiversity. The external Alps have played a major role in the maintenance of populations near the central Alps during the Last Glacial Maximum and influenced the evolution of the species, and of vegetation. Polytopic autopolyploidy in different biogeographic districts is also demonstrated. The species has had an important and rapid radiation because recolonisation took place from different refugia. The subsequent recolonisation of the Western Alps was achieved by independent lineages that are presently admixing in the central Alps. The role of the Pennic summit line is underlined as a great barrier that was permeable only through certain favourable high-altitude passes. The central Alps are thus viewed as an important crossroad where genomes with different evolutionary histories are meeting and admixing. The AFLP analysis and comparison of local populations growing in contrasted ecological and historical situations indicate that populations persisting in the external Alps present restricted gene dispersal and low genetic diversity but seem in equilibrium with their environment. On the contrary, populations colonising the attitudinal margin are mainly influenced by founder effects together with great gene dispersal and genotypes have a nearly random distribution, suggesting that recolonisation is not associated with adaptive processes. Autopolyploids that locally persist against climate changes thus seem to present adaptive ability, while those that actively recolonise the Alps are successful because of their great capacity to maintain a high genetic diversity against founder effects during recolonisation.