In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits and population differentiation in the insect-pollinated, self-incompatible, perennial herb Primula farinosa. More specifically, I (1) determined whether the effects of floral display and interactions with pollinators and seed predators, and plant reproductive success were frequency-dependent and affected by surrounding vegetation context, (2) examined the consequences of intermittent drought years on population dynamics using numerical simulations based on demographic data collected over seven years, (3) analyzed among-population differentiation in flowering phenology and reproductive allocation, and its relationship to soil-depth at the site of origin. A field experiment suggested that conspicuous plants facilitate inconspicuous plants in terms of pollinator attraction, and that the facilitation effect is contingent on the height of the surrounding vegetation. Further experiments revealed that both mutualistic and antagonistic interactions can result in frequency-dependent selection on floral display. Among inconspicuous plants, both fruit initiation, and damage from seed predators increased with the proportion of the conspicuous morph. The relative strength of these effects, and therefore their net outcome on the relationship between morph ratio and seed production varied among years. I combined information on vital rates and their relation to environmental conditions in simulations to predict future population viability in changing environments. Simulated stochastic population growth rate decreased with increasing frequency of drought years. Reproductive allocation varied significantly among populations both in the field and in a common-garden experiment, but was correlated with soil depth at the site of origin only in the field. The results suggest that among-population variation in reproductive effort in the field mainly reflects plastic responses to environmental conditions, and that this plasticity may be adaptive. The common-garden experiment suggested that the study populations have diverged genetically in flowering time.

Studying genetic diversity in natural and domestic populations is of major importance in evolutionary biology. The recent advent of next generation sequencing (NGS) technologies has dramatically changed the scope of these studies, enabling researchers to study genetic diversity in a whole-genome context. This thesis details examples of studies using NGS data to: (i) characterize evolutionary forces shaping the genome of the Atlantic herring, (ii) detect the genetic basis of speciation and domestication in the rabbit, and, (iii) identify mutations associated with skeletal atavism in Shetland ponies. The Atlantic herring (Clupea harengus) is the most abundant teleost species inhabiting the North Atlantic. Herring has seasonal reproduction and is adapted to a wide range of salinity (3-35‰) throughout the Baltic Sea and Atlantic Ocean. By using NGS data and whole-genome screening of 20 populations, we revealed the underlying genetic architecture for both adaptive features. Our results demonstrated that differentiated genomic regions have evolved by natural selection and genetic drift has played a subordinate role. The European rabbit (Oryctolagus cuniculus) is native to the Iberian Peninsula, where two rabbit subspecies with partial reproductive isolation have evolved. We performed whole genome sequencing to characterize regions of reduced introgression. Our results suggest key role of gene regulation in triggering genetic incompatibilities in the early stages of reproductive isolation. Moreover, we studied gene expression in testis and found misregulation of many genes in backcross progenies that often show impaired male fertility. We also scanned whole genome of wild and domestic populations and identified differentiated regions that were enriched for non-coding conserved elements. Our results indicated that selection has acted on standing genetic variation, particularly targeting genes expressed in the central nervous system. This finding is consistent with the tame behavior present in domestic rabbits, which allows them to survive and reproduce under the stressful non-natural rearing conditions provided by humans. In Shetland ponies, abnormally developed ulnae and fibulae characterize a skeletal deformity known as skeletal atavism. To explore the genetic basis of this disease, we scanned the genome using whole genome resequencing data. We identified two partially overlapping large deletions in the pseudoautosomal region (PAR) of the sex chromosomes that remove the entire coding sequence of the SHOX gene and part of CRLF2 gene. Based on this finding, we developed a diagnostic test that can be used as a tool to eradicate this inherited disease in horses.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Le groupe ‘M. mycoides’ constitue une branche phylogénétique homogène des mycoplasmes regroupant 6 taxons pathogènes des ruminants, responsables pour la plupart de maladies inscrites sur la liste de l’OIE. L’identification taxinomique sur laquelle repose le diagnostic reste délicate à cause de réactions antigéniques et génétiques croisées et d’un manque d’universalité intra-taxon des PCR, notamment pour les taxons Mcc, MmmLC et Mbg7. Une approche par hybridation soustractive sélective a été développée pour 1) appréhender les différences moléculaires entre ces 3 taxons ; 2) analyser globalement la diversité au sein du groupe ‘M. mycoides’ et 3) rechercher de nouveaux marqueurs d’intérêt diagnostique. Nos résultats montrent un important partage de séquences entre ces taxons, MmmLC et Mcc étant très polymorphes par rapport à Mbg7, plus homogène et qui représente une sorte de chimère entre les taxons Mcc et MmmSC. Nos données nous ont permis de développer un test PCR spécifique pour Mcc mais la diversité génétique du groupe ‘M. mycoides’ dépasse les frontières entre taxons rendant difficile et peu pertinente l’identification taxinomique. Un typage des souches en fonction de la virulence indépendamment de l’espèce serait l’approche diagnostique alternative. La faisabilité d’une telle approche a été explorée dans le cas du taxon MmmLC mais aucun critère susceptible de différencier les souches issues de foyers de celles issues de portage dans des troupeaux sans antécédent clinique n’a pu être mis en évidence. Ce continuum génétique entre souches, probablement lié à des transferts génétiques horizontaux, imposera à l’avenir une surveillance globalisée des mycoplasmoses / The ‘M. mycoides’ cluster, a homogenous phylogenetic branch of the Mollicutes, includes 6 taxa which are responsible for diseases in ruminants, most of which are listed by the OIE. Their taxonomic identification, on which current diagnosis is based, is impaired by antigenic and genetic cross-reactivity and by the lack of a universal, intra-taxon PCR assay, especially for the Mcc, MmmLC and Mbg7 taxa. A suppression subtractive hybridization approach was developed to: 1) define molecular differences between these 3 taxa; 2) analyze the overall genetic diversity within the ‘M. mycoides’ cluster and 3) search for new markers useful for diagnosis. Results obtained here showed that several sequences are shared across taxa, with Mcc and MmmLC being very polymorphic compared to Mbg7 which is more homogeneous, representing a sort of chimera between Mcc and MmmLC. From these analyses, a specific PCR assay was designed for Mcc identification but, because of the genetic diversity existing within the ‘M. mycoides’, the taxonomic identification of new strain appears less and less relevant. Instead, regardless of their species, strain typing on the basis of their virulence would offer an alternative approach for diagnosis. We assessed this type of approach for the MmmLC taxon but so far, our attempts to uncover markers that would distinguish pathogenic strains from carrier strains, isolated from herds with no clinical history, have failed. The genetic continuum observed between strains is remnant of horizontal gene transfers and imposes the development of a more global approach for mycoplasmosis surveillance

La gorgone rouge, Paramuricea clavata (Cnidaire, Octocoralliaire), est une espèce sessile, longévive à faible croissance dont les populations présentent une lente dynamique. Cette espèce est caractérisée par une phase larvaire pélagique qui représente l’unique phase de dispersion potentielle au cours du cycle de vie de cette espèce. P. clavata est une espèce clé des assemblages à coralligène de Méditerranée, qui subit les effets combinés des activités de plongée sous-marine et du changement climatique. Dans ce contexte, il était donc fondamental d’approfondir les connaissances sur les traits d’histoire de vie, la biologie et l’écologie de cette espèce. L’objectif de ce travail était d’étudier, à l’aide d’une approche génétique, les facteurs biologiques et écologiques clés qui devraient être importants pour la réponse de l’espèce aux changements environnementaux. Parmi ces facteurs, la dispersion larvaire joue un rôle fondamental dans la dynamique et la connectivité des populations marines. Dans le contexte actuel des fortes pressions anthropiques, la compréhension des degrés de connectivité entre les populations est primordiale pour évaluer le devenir des populations, face au changement climatique, et pour mettre en place des plans de conservation et des réseaux d’aires marines protégées. / The red gorgonian, Paramuricea clavata (Cnidaria, Octocorallia), is a sessile, long-lived and slow growing species which displays slow population dynamics. This species is characterized by a pelagic larval phase that represents the sole potential phase of dispersal during the life cycle of this species. P. clavata is a key species of coralligenous assemblages of the Mediterranean Sea which undergoes the combined effects of diving activities and climate change. In this context, extending the knowledge about life history traits, biology and ecology of the red gorgonian was of fundamental importance. Using a genetic approach, the goal of this work was to study some key biological and ecological factors which should be important for the response of this species to environmental changes. Among these factors, larval dispersal plays a major role in driving marine population dynamics and connectivity. In the current context of strong anthropic pressures, understanding the level of population connectivity is primordial to evaluate population outcome, facing climate change, and to develop conservation plans as well as to design marine reservenetworks.

La forte variation climatique, notamment de la température qui est associée à la distribution altitudinale de certains peuplements d’arbres forestiers peut induire des pressions de sélection divergentes favorisant l’expression de phénotypes différents en fonction de l’altitude. Cette thèse a pour objectif de déterminer si des adaptations locales existent et peuvent être mises en évidence dans un peuplement de mélèze (Larix decidua Mill.) distribué le long d’un gradient altitudinal situé dans les Alpes françaises, à proximité de Briançon. Quatre placettes d’environ 200 mélèzes ont été délimitées à 2300 m, 2000 m, 1700 m et 1350 m d’altitude le long de ce gradient. Une variabilité phénotypique significative a été observée entre ces niveaux altitudinaux pour la plupart des caractères étudiés : circonférence, hauteur de l’arbre, pourcentage d’aubier ainsi que pour toutes les variables microdensitométriques de cernes sauf une (la largeur de cerne). Une analyse de génétique des populations utilisant des marqueurs microsatellites a mis en évidence une faible influence de la dérive génétique sur la diversité génétique et une forte intensité de flux de gènes entre les différents niveaux altitudinaux étudiés. La différenciation génétique inter-altitudes a été estimée à l’aide d’une approche in-situ basée sur les données phénotypiques seules (PST) et comparée à la différenciation observée à l’aide des marqueurs microsatellites (FST). Cette analyse indique que l’hypothèse d’adaptations locales avec l’altitude peut être raisonnablement avancée pour les caractères de hauteur, circonférence, pourcentage d’aubier et densité du bois initial. Au contraire, l’adaptation locale n’apparait pas comme une hypothèse acceptable pour les caractères de largeur de cerne, surface de cerne, largeur du bois final et densité du bois final. / The strong climatic variation, in particular the temperature variation, which is associated with the altitudinal distribution of certain stands of forest trees, can induce different divergent selection pressure favoring altitude-dependent phenotype expression. The aim of the present thesis is to determine if local adaptation exists and can be identified in an European larch stand (Larix decidua Mill.) distributed along an altitudinal gradient located in the French Alps near Briançon. four plots of about 200 larches were delimited at 2300 m, 2000 m, 1700 m and 1350 m along this altitudinal gradient. A significant phenotypic variability was observed between these altitudinal levels for most characters studied: circumference, tree height, percentage of sapwood and for all the annual-ring microdensity variables except one (ring width). A population genetics analysis using microsatellite markers showed a small effect of genetic drift on the genetic diversity but an intensive gene flow between the altitudinal levels studied. The inter-altitudinal genetic differentiation was estimated using an in-situ approach based on phenotypic data only (PST) and compared with the differentiation observed by means of microsatellite markers (FST). This analysis indicates that the assumption of local adaptation with altitude can be reasonably proposed for the characters of height, circumference, percentage of sapwood and earlywood density. On the contrary, the local adaptation does not appear to be an acceptable assumption concerning characters such as ring width, ring surface area, latewood width and latewood density.

La diversité génétique est un élément majeur pour l'évolution des espèces dans un environnement changeant. Chez les isopodes Armadillidium vulgare et Porcellionides pruinosus, l'infection par Wolbachia engendre une féminisation des mâles pouvant entraîner des sex-ratios fortement biaisés en faveur des femelles. Cela réduit la taille efficace des populations infectées qui peut provoquer une réduction de la diversité génétique. Cependant, chez A. vulgare, il existe un maintien de cette diversité qui pourrait être dû à des prévalences trop faibles de Wolbachia pour impacter les populations ou à d’autres facteurs comme par exemple lors de la reproduction un choix préférentiels des mâles pour les femelles génétiques. Un suivi des prévalences de Wolbachia dans des populations naturelles d’A. vulgare a été réalisé sur plusieurs années à partir d’une nouvelle méthode basée sur le génotypage. Les résultats montrent (i) des infections multiples de Wolbachia et (ii) des prévalences faibles pour wVulM, wVulC et wVulP. La présence d'un second facteur féminisant appelé f est suspectée dans de nombreuses populations. A l’échelle individuelle, Wolbachia semble avoir un impact sur le nombre de multi-paternités puisque les femelles génétiques s’accouplent avec plus de mâles que les néo-femelles. Les faibles prévalences de Wolbachia et les accouplements multiples permettent de maintenir une diversité génétique importante au sein des populations d’A. vulgare. Chez P. pruinosus, les prévalences de Wolbachia sont élevées et on observe de forts taux de consanguinité. Cependant, ces taux pourraient également résulter de fluctuations d’effectifs dans ces populations liées à un habitat spécialisé et peu stable. / Genetic diversity is a crucial component for the evolution of species in changing environments. In the isopods Armadillidium vulgare and Porcellionides pruinosus, infection with Wolbachia bacteria causes a feminization of males that could lead to strongly female-biased sex-ratios. This reduces the effective size of infected populations and may result in a decreased genetic diversity. Nevertheless, genetic diversity is known to be maintained in A. vulgare. This might be due to Wolbachia prevalences being too low to impact host populations, or to other factors, as for example males preferentially choosing genetic females for reproduction. Wolbachia prevalence has been monitored over several years in natural populations of A. vulgare using a new genotyping method. The results demonstrate (i) multiple Wolbachia infections and (ii) low prevalences of wVulM, wVulC and wVulP. The presence of a second feminizing factor, called f, is suspected in numerous populations. At the individual scale, Wolbachia seems to have an effect on the number of multiple paternities, since genetic females mate with more males than neo-females. Low Wolbachia prevalence and multiple mating may allow the maintenance of a high genetic diversity in A. vulgare populations. In P. pruinosus, Wolbachia prevalences are high and we observe high consanguinity rates. However, these rates might also result from fluctuations in population size due to a specialized and unstable habitat.

Leifsonia xyli subsp. xyli (Davis et al.; 1984; Evtushenko et al.; 2000) é agente causal de uma das mais importantes doenças da cana-de-açúcar: o raquitismo-da-soqueira (Gillaspie Jr. & Davis, 1992; Davis et al.; 1994). O presente trabalho teve como objetivo principal usar métodos de análise cromossômica para corroborar o mapa genômico da estirpe CTC B07 de L. xyli subsp. xyli obtido através do seqüenciamento por "shotgun", realizado pelo grupo de seqüenciamento de Genomas Agronômicos e do Meio-ambiente (AEG) da rede ONSA-FAPESP. A identidade do isolado foi confirmada com a amplificação e seqüenciamento da região 23S do rRNA bem como por meio de testes sorológicos de microaglutinação com antissoro específico. Além destes, foram realizados testes de microscopia eletrônica de varredura da bactéria cultivada em meio líquido para confirmar a pureza do isolado. O tamanho do genoma de L. xyli subsp. xyli foi estimado com base na análise de fragmentos de restrição gerados por digestões com as enzimas de restrição XbaI e SpeI e eletroforese de campo pulsado (PFGE). As estimativas de 2.540 kb e 2.530 kb com XbaI e SpeI respectivamente ficaram próximas ao valor obtido pelo seqüenciamento genômico (2.596.959 pb). Em adição, o número de seqüências repetidas e de genes ribossomais identificados pelo projeto genoma foram confirmados por meio de hibridizações com sondas apropriadas. Comparações genômicas de L. xyli subsp. xyli, L. xyli subsp. cynodontis e duas espécies de Clavibacter também foram objetivos deste trabalho. As comparações foram baseadas em análise de RFLPs após a hibridização do DNA genômico utilizando como sondas elementos genéticos móveis presentes no genoma de L. xyli subsp. xyli. As estimativas dos números estimado de cópias destes elementos no genoma de L. xyli subsp. xyli obtidas por hibridizações concordam com aquelas obtidas pelo seqüenciamento, considerando fragmentos RFLPs menores que 9 kb. Informações referentes à fragmentos maiores não foram obtidas uma vez que estes não foram adequadamente resolvidos na corrida eletroforética. Finalmente, comparações através de análise de RFLP e rep-PCR mostraram diferenças entre L. xyli subsp. xyli e L. xyli subsp. cynodontis bem como entre estas e espécies de Clavibacter. Não foram verificadas diferenças entre a estirpe CTC B07 de L. xyli subsp. xyli e a estirpe australiana. / Leifsonia xyli subsp. xyli (Davis et al.; 1984; Evtushenko et al.; 2000) is the causal agent of one of the most economically important disease of sugarcane worldwide, i.e, ratoon stunting disease (Gillaspie Jr. & Davis, 1992; Davis et al.; 1994). The main objective of this study was to confirm the assembly of the genome of L. xyli subsp. xyli obtained after shotgun sequencing by the Agronomic and Enviromental Genomes group of the ONSA/FAPESP network. The identity of the strain was confirmed by amplification and sequencing of the 23S rRNA region as well as by microaglutination serological tests with specific antiserum. Besides this, scanning electron microscopic analysis was used to assess the purity of the strain culture. The size of the genome of L. xyli subsp. xyli was estimated based on restriction analysis after digestion of genomic DNA with SpeI and XbaI followed by pulsed-field gel electrophoresis. The estimates of 2,530 kb and 2,540 kb, respectively for SpeI and XbaI, are in agreement with the one obtained by whole genome sequencing (2,596 kb). In addition, the number of repeated sequences and ribossomal genes predicted by thesequencing project was confirmed by hybridization experiments with the appropriate probes. Genomic comparisons of L. xyli subsp. xyli, L. xyli subsp. cynodontis and two Clavibacter species comprised a second objective of this study. Comparisons were based on RFLP analysis after hybridization of digested genomic DNA using mobile genetic elements present in the genome of L. xyli subsp. xyli as probes. The estimates of number of copies of these elements in the genome of L. xyli subsp. xyli obtained by this approach agreed with the ones obtained by sequencing if RFLP fragments smaller than 9 kb are considered. Data from larger fragments were not obtained since they were not adequately resolved by electrophoresis. Finally, RFLP and rep-PCR comparisons unveiled differences between L. xyli subsp. xyli and L. xyli subsp. cynodontis as well as between these and Clavibacter. No differences were found between strain CTC B07 of L. xyli subsp. xyli and an Australian strain.

Linhagens de Escherichia coli enterotoxigênica (ETEC) são consideradas como importante agente de diarréia, principalmente entre crianças e turistas em países em desenvolvimento. Entre os fatores de virulência expressos por ETEC, as enterotoxinas termo-lábil (LT) e termo-estável (ST) representam os mais relevantes fenótipos. Evidências preliminares sugerem que a severidade da diarréia associada a linhagens de ETEC deve refletir a diversidade natural de linhagens selvagens quanto à produção de enterotoxinas e/ou à ocorrência de variantes naturais com efeitos tóxicos reduzidos. No presente trabalho, investigamos diversidade genética do óperon etx, que codifica para a toxina LT, e da capacidade de produção e secreção de LT por linhagens de ETEC isoladas de humanos ou suínos em diferentes regiões geográficas. Os resultados mostraram considerável variabilidade na produção de LT com valores variando de 2 a 2.525 ng de toxina por mL de cultura. Secreção de LT foi também variável com valores variando de menos que 0,04% a 49,5% do total de LT produzida pelas diferentes linhagens de ETEC. Adicionalmente, experimentos de alça ligada em coelho mostraram uma boa correlação entre a quantidade de LT secretada sob condições in vitro e a capacidade de causar acúmulo de fluidos in vivo. Nós determinamos ainda diversidade de ETEC pela obtenção das seqüências dos óperons etxAB de 50 linhagens (LT+ or LT+/ST+) pertencentes a diferentes sorotipos com ênfase para as linhagens produtoras apenas de LT e isoladas de crianças assintomáticas. As seqüências de nucleotídeo completas dos genes etxAB revelaram 23 alterações de aminoácidos nas subunidades A (18) e B (5), as quais geraram 16 variantes de LT. Entre estes variantes de LT, um mostrou efeito tóxico reduzido em comparação à toxina de referência LT1. A forma de LT atenuada (LT4) tem atividade enzimática reduzida devido à troca de aminoácido. / Enterotoxigenic Escherichia coli (ETEC) strains represent an important etiological agent of diarrheal disease, particularly among children and travelers in developing countries. Among the virulence factors expressed by ETEC strains the heat-labile (LT) and heat-stable (ST) enterotoxins represent the most revelevant phenotypes. Indirect evidences suggest that the severity of diarrhea associated to ETEC strains might reflect the natural diversity of wild strains to produce enterotoxins and/or the occurrence of variants endowed with reduced toxic effects. In the present study, we investigated both the genetic diversity of the etx operon, encoding the heat-labile toxin, and the capability to produce/secrete LT by ETEC strains isolated from humans or porcine in different geoghrafic areas. The results showed a remarkable variability on the production of LT with values ranging from 2 to 2,525 ng of toxin per ml of culture. LT secretion was also variable with values ranging from less than 0.04% to 49.5% of total LT produced by the different ETEC strains. Additionally, rabbit ileal loop experiments showed a good correlation between the amounts of secreted LT under in vitro conditions and fluid accumulation in vivo. We determined also the diversity of the etxAB operon of 50 ETEC strains (LT+ or LT+/ST+) belonging to different serotypes with emphasis to LT+-only producing strains isolated from asymptomatic children. The complete nucleotide sequences of the etxAB genes revealed 23 amino acid changes at the A (18) or B (5) subunits, which generated 16 variant forms of LT. Among these LT variants, one of them showed reduced toxic effects in comparison to the reference toxin LT1. The attenuated LT form (LT4) had decreased enzymatic activity due to an amino acid replacement (K4R) at the A1 subunit. LT4 retains its immunogenic and adjuvant properties following nasal immunization. Additionaly, the LT4 variant showed altered immune modulatory features and promoted a more biased Th1 response, which favor activation of effector CD8+ T lymphocytes, to co-administred antigen with regard to LT1. Taken together, our results demonstrate that ETEC strains isolated from human subjects express natural genetic variability leading to a remarkable polymorphism of the etx operon as well as production and secretion of LT. Such natural genetic diversity observed in ETEC strains may affect the host-pathogen relationships and, consequently, contribute to the severity of the disease among infected subjects.

O palmiteiro (Euterpe edulis Mart.) é uma espécie nativa da Mata Atlântica cujas populações naturais encontram-se degradadas pelo extrativismo. Considerando a escassez de informações relativas às conseqüências genéticas da exploração de palmito, o objetivo deste estudo foi avaliar o impacto do processo de exploração sobre os níveis de diversidade, estrutura genética e tamanho efetivo de populações da espécie. Também foram estudados aspectos genéticos do recrutamento de plantas e o sistema reprodutivo da espécie. O estudo foi realizado em duas localidades do Estado de Santa Catarina, nos municípios de São Pedro de Alcântara e Ibirama. Em cada localidade foram escolhidas duas áreas de ocorrência natural de E. edulis, uma sem influência antrópica e outra que sofreu exploração de palmito, totalizando quatro populações. Os sistemas de exploração foram: (i) extrativismo - onde todos os indivíduos acima de 2 m de altura são cortados, incluindo plantas reprodutivas; and (ii) manejo - onde somente indivíduos acima de 9 cm de DAP são cortados, com a manutenção de 50 plantas reprodutivas por hectare. Em cada população foram examinadas plântulas, jovens e adultos, usando oito locos microssatélites e dez locos alozímicos. Os resultados revelaram que a espécie se reproduz por alogamia ( m tˆ = 0,996 para microssatélites e m tˆ = 1,000 para isoenzimas), porém a ocorrência de cruzamentos entre indivíduos aparentados (até 5%) e cruzamentos biparentais (10%) indica a ocorrência de cruzamentos não aleatórios. Em locos alozímicos, observaram-se as seguintes amplitudes de variação das estimativas de diversidade entre as categorias: Aˆ : 3,05 a 3,15; e Hˆ : 0,416 a 0,431; o Hˆ : 0,378 a 0,403. Em locos microssatélites, a variação observada foi a seguinte: Aˆ : 14,12 a 14,72; e Hˆ : 0,781 a 0,785; o Hˆ : 0,678 a 0,709. Nas populações não exploradas, houve um aumento na freqüência de heterozigotos na direção do estádio adulto, o que sugere a ação da seleção favorecendo o aumento de heterozigotos. Valores altos e significativos do índice de fixação ( fˆ ) foram observados, especialmente nos marcadores microssatélites, indicando desvios do equilíbrio de Hardy-Weinberg. De modo geral, ambos os marcadores revelaram um aumento dos valores de fˆ nas populações exploradas, especialmente entre as plântulas. As estimativas ST Gˆ e ST Rˆ não revelaram alterações na estrutura genética das populações exploradas e demostraram uma divergência genética inferior a 5% na maioria das comparações aos pares, em ambos os marcadores. O tamanho efetivo ( e Nˆ ) dos indivíduos adultos por hectare foi superior a 110 nas populações não pertubadas, enquanto nas populações exploradas, o tamanho efetivo por hectare foi reduzido para 45, sob manejo, e 14, sob extrativismo. Porém, o tamanho efetivo total das populações exploradas ainda é elevado, o que explica a manutenção dos altos níveis de diversidade nessas populações. Finalmente, a informação genética conjunta desses marcadores demonstrou que os efeitos da exploração foram pouco pronunciados até o momento em relação aos níveis de diversidade e estrutura genética das populações de E. edulis. Entretanto, a redução da população de cruzamentos resultou em alterações no comportamento reprodutivo dos indivíduos, promovendo um aumento nos níveis de endogamia nas coortes mais jovens das populações exploradas. Contudo, os resultados obtidos neste estudo indicaram questões adicionais a serem estudadas. Em função do elevado nível de variabilidade dos locos microssatélites observado em E. edulis, recomenda-se aumentar o tamanho das amostras visando otimizar a informação genética proporcionada por esses marcadores. Além disso, novos estudos são necessários sobre os efeitos do manejo tecnificado, uma vez que os resultados obtidos podem ter sido influenciados por outros eventos de exploração ocorridos no passado e pelas populações existentes nas proximidades devido ao elevado fluxo gênico da espécie. / Heart-of-palm tree (Euterpe edulis Mart.; Arecaceae) is a native species of the Atlantic forest whose natural populations are degraded by extractivism. Regarding the relative scarcity of information on the genetic consequences of palm heart exploitation, the aim of this study was to investigate the effects of two exploitation systems - extractivism and management - on the levels of variability, genetic structure and effective size of Euterpe edulis Mart. populations. We also investigated genetic aspects of the plant recruitment and the reproductive system of the species. Four natural populations of E. edulis with different histories of disturbance were surveyed in the districts of São Pedro de Alcântara and Ibirama, Santa Catarina, Brazil. At both sites, we sampled an undisturbed and an exploited population. The exploitation systems were: (i) extractivism - where most individuals higher than 2 m are harvested, including reproductive plants; and (ii) management - where only individuals with more than 9 cm of DBH are harvested, with the maintainance of 50 reproductive plants per ha. Three categories of plants, from seedlings to adults, were examined using eight microsatellite loci and ten allozyme loci. Results demonstrated the preferentially allogamic behaviour of the species ( m tˆ = 0.996 for microsatellites and m tˆ = 1.000 for allozymes), but the occurrence of matings among related individuals (5%) and biparental matings (10%) indicated the existence of non-random matings in this species. For allozymic loci, the following diversity estimates were obtained among the categories: Aˆ : 3.05 to 3.15; e Hˆ : 0.416 to 0.431; o Hˆ : 0.378 to 0.403. For microsatellites, the estimates were as follows: Aˆ : 14.12 to 14.72; e Hˆ : 0.781 to 0.785; o Hˆ : 0.678 to 0.709. In undisturbed populations, there was an increase in heterozygote frequency towards the adult stages, suggesting the action of natural selection favouring such heterozygote increase. Highly significant values of fixation index ( fˆ ) were observed, mainly at microsatellite loci, indicating departures from Hardy-Weinberg expectation. Both markers displayed an increase of fˆ values in the exploited populations, especially for seedlings. The estimates of interpopulation genetic variation ( ST Gˆ ; ST Rˆ ) revealed that more than 95% of the molecular genetic variability of the species is distributed within populations, and there was no evidence of changes in genetic structure of the exploited populations. Effective size ( e Nˆ ) per hectare of the adult individuals was higher than 110 in the two undisturbed populations, while in the exploited populations the effective size per hectare was reduced to 45 under management, and 14 under extractivism. However, the total effective size of the exploited populations was still high, which explains the maintenance of high diversity levels in these populations. Finally, the genetic information from both markers displayed small pronounced effects of the exploitation process on variability and population genetic structure of E. edulis, with the exception of an increase in the inbreeding levels among seedlings and juveniles of the exploited populations. However, our results raised further questions for study. Because of the hypervariability of microssatellite loci used in this work, we would recommend an increase in the sample size (>100) in order to optimize the genetic information provided by these markers. Moreover, new investigations are necessary on the effects of management, since the results from this study could have been influenced by other exploitation events that have occurred in the past and by the existence, due to the high gene flow of the species, of surrounding undisturbed populations.