Among the number of examples of broad radiations of insects on plants, the fig fig wasp system is one of the most remarkable. Although this interaction has frequently been used as a model for studies of mutualism and coevolution, other groups of insects associated with fig trees have received less attention. The weevils (Coleoptera: Curculionidae) associated with figs are one notable example. Being the largest family of animals, weevils achieved great evolutionary success due to their early association with their host plants. Despite few reports in literature, there is strong evidence of the specialization of weevils on figs. The main objective of this thesis was to understand how diversification of Curculionidae took place in fig trees. Previous studies have never addressed the systematics and biogeography of fig weevils under a phylogenetic framework. Therefore, we analyzed the tempo of diversification of Curculionidae lineages that use fig trees as host in order to reconstruct their historical biogeography. To gather information on fig weevils, we collected 325 fruit sets from more than 12% of the total Ficus species, from the Neotropical, Afrotropical and Oriental regions. We also examined seven entomological collections (AMNH, BMNH, INBIO, MNHN, MZUSP, NMNH, SAMC) searching for weevil specimens collected on figs. At least 80 weevil species from five genera (Cetatopus, Omophorus, Carponinus, Curculio, and Indocurculio) were found to be associated with figs. The radiation of curculionids on figs occurred at least three times independently. The tempo of diversification of the crown fig weevils is congruent with the diversification of figs during the Upper-Cretaceous/Lower-Eocene period. We hypothesize that the variation of the sea level and warmer climate in the past had great influence on the evolution of the species. Our results encourage future research on the biology and ecology of these species and will help us to understand the role weevils may have played in the evolution of the fig- fig wasp mutualism. / Um dos mais notáveis exemplos de radiação adaptativa de insetos em classes de plantas é o sistema figueiras - vespas de figo. Embora essa interação tenha sido frequentemente usada como modelo nos estudos de mutualismo e coevolução, outros grupos de insetos relacionados às figueiras têm sido negligenciados. Besouros curculionídeos (Coleoptera: Curculionidae) associados a figueiras representam um desses grupos pouco estudados. Apesar dos relatos escassos na literatura, existem fortes evidências do alto grau de especialização destes besouros às suas plantas hospedeiras. O objetivo geral desta tese foi entender como se deu a diversificação dos curculionídeos sobre as figueiras. Trabalhos anteriores nunca utilizaram uma abordagem filogenética para estudar a sistemática e biogeografia dos curculionídeos de figo e, por isso, este estudo analisa o tempo de diversificação das linhagenes destes besouros para reconstruir sua biogeografia histórica. De modo a obter informações das espécies estudadas, foram coletadas 325 amostras de frutos de cerca de 12% do total de espécies de figueiras das regiões Neotropical, Afrotropical e Oriental. Sete coleções entomológicas (AMNH, BMNH, INBIO, MNHN, MZUSP, NMNH, SAMC) foram vistadas em busca de espécimes de curculionídeos coletados em figo. Pelo menos 80 espécies de cinco gêneros (Cetatopus, Omophorus, Carponinus, Curculio e Indocurculio) foram encontradas. A radiação dos curculionídeos de figo ocorreu independentemente pelo menos três vezes ao longo da história dos Curculionidae. O período de diversificação das linhagenes de curculionídeos de figo é fortemente congruente com o período de diversificação das linhagenes de figueiras durante o fim do Cretáceo/Paleoceno. Acredita-se que fatores como a forte variação no nível dos oceanos e o clima mais quente no passado tiveram grande influência na evolução das espécies. Espera-se que os resultados deste trabalho encorajem estudos futuros sobre a biologia e ecologia dos curculionídeos associados às figueiras e auxilie no entendimento do papel que os curculionídeos possam ter desempenhado na evolução do sistema Ficus - vespas de figo.

Cancer related mortality is almost always due to metastatic dissemination of the primary disease. While research into the biological mechanisms that drive the metastatic cascade continues to unravel its molecular underpinnings, progress in our understanding of biological phenomena such as tumour heterogeneity and its relevance to the origins of distant recurrence or the emergence of resistance to therapy has been limited.In parallel to major breakthroughs in the development of high throughput molecular techniques, researchers have begun to utilise next generation sequencing to explore the relationship between primary and matched metastatic tumours in diverse types of neoplasia. Despite small cohort sizes and often, a limited number of matched metastases for each patient, pioneering studies have uncovered hitherto unknown biological processes such as the occurrence of organ specific metastatic lineages, polyclonal seeding and homing of metastatic cells to the primary tumour bed. While yet other studies continue to highlight the potential of genomic analyses, at the time this thesis was started, an in-depth knowledge of disease progression and metastatic dissemination was currently lacking in breast cancers.Herein, we employed phylogenetic inference methods to investigate intra-tumour heterogeneity and evolution of breast cancers. A combination of whole exome sequencing, custom ultra-deep resequencing and copy number profiling were applied to primary tumours and their associated metastases from ten autopsied breast cancer patients. Two modes of metastatic progression were observed. In the majority of cases, all distant metastases clustered on a branch separate from their primary lesion. Clonal frequency analysis of somatic mutations showed that the metastases had a monoclonal origin and descended from a common metastatic precursor. Alternatively, the primary tumour was clustered alongside metastases with early branches leading to distant organs. This dichotomy coincided with the clinical history of the patients whereby multiple seeding events from the primary tumour alongside cascading metastasis-to-metastasis disseminations occurred in treatment naïve de novo metastatic patients, whereas descent from a common metastatic precursor was observed in patients who underwent primary surgery followed by systemic treatment. The data also showed that a distant metastasis can be horizontally cross-seeded and finally revealed a correlation between the extent of somatic point mutations private to the distant lesions and patient overall survival. In an unrelated dataset of relapsed breast cancer patients with matched primary and distant lesions profiled using whole genome sequencing, the landscape of somatic alterations confirmed the time dependency of copy number aberrations implying that cancer phylogenies can be dated using a molecular clock.The work presented here harnesses the strength of high throughput genomic techniques and state of the art phylogenetic tools to tell the evolutionary history of breast cancers. Our results show that the linear and parallel models of metastatic dissemination which have been held as near doctrines for many years are overstated point of views of cancer progression. Beyond the biological insights, these results suggest that surgical excision of the primary tumour in de novo metastatic breast cancers might reduce dissemination in selected cases hence providing a potential biological rationale for this practice. Similarly, there is no strong evidence of benefit in overall survival from surgical resection of oligo-metastases in breast cancer. From our analyses, metastatic lesions constitute an additional source of seeding and heterogeneity in advanced breast cancer. The data presented here is too small to derive practice-changing evidence, but supports the concept that resecting isolated metastases may be of clinical benefit in oligo-metastatic breast cancer patients. In both cases, results from larger prospective studies are warranted. / Doctorat en Sciences biomédicales et pharmaceutiques (Médecine) / info:eu-repo/semantics/nonPublished

<p>This thesis concerns different aspects of dating divergence times in phylogenetic trees, using molecular data and multiple fossil age constraints.</p><p>Datings of phylogenetically basal eudicots, monocots and modern birds (Neoaves) are presented. Large phylograms and multiple fossil constraints were used in all these studies. Eudicots and monocots are suggested to be part of a rapid divergence of angiosperms in the Early Cretaceous, with most families present at the Cretaceous/Tertiary boundary. Stem lineages of Neoaves were present in the Late Cretaceous, but the main divergence of extant families took place around the Cre-taceous/Tertiary boundary.</p><p>A novel method and computer software for dating large phylogenetic trees, PATHd8, is presented. PATHd8 is a nonparametric smoothing method that smoothes one pair of sister groups at a time, by taking the mean of the added branch lengths from a terminal taxon to a node. Because of the local smoothing, the algorithm is simple, hence providing stable and very fast analyses, allowing for thousands of taxa and an arbitrary number of age constraints.</p><p>The importance of fossil constraints and their placement are discussed, and concluded to be the most important factor for obtaining reasonable age estimates.</p><p>Different dating methods are compared, and it is concluded that differences in age estimates are obtained from penalized likelihood, PATHd8, and the Bayesian autocorrelation method implemented in the multidivtime program. In the Bayesian method, prior assumptions about evolutionary rate at the root, rate variance and the level of rate smoothing between internal edges, are suggested to influence the results.</p>

This thesis concerns different aspects of dating divergence times in phylogenetic trees, using molecular data and multiple fossil age constraints. Datings of phylogenetically basal eudicots, monocots and modern birds (Neoaves) are presented. Large phylograms and multiple fossil constraints were used in all these studies. Eudicots and monocots are suggested to be part of a rapid divergence of angiosperms in the Early Cretaceous, with most families present at the Cretaceous/Tertiary boundary. Stem lineages of Neoaves were present in the Late Cretaceous, but the main divergence of extant families took place around the Cre-taceous/Tertiary boundary. A novel method and computer software for dating large phylogenetic trees, PATHd8, is presented. PATHd8 is a nonparametric smoothing method that smoothes one pair of sister groups at a time, by taking the mean of the added branch lengths from a terminal taxon to a node. Because of the local smoothing, the algorithm is simple, hence providing stable and very fast analyses, allowing for thousands of taxa and an arbitrary number of age constraints. The importance of fossil constraints and their placement are discussed, and concluded to be the most important factor for obtaining reasonable age estimates. Different dating methods are compared, and it is concluded that differences in age estimates are obtained from penalized likelihood, PATHd8, and the Bayesian autocorrelation method implemented in the multidivtime program. In the Bayesian method, prior assumptions about evolutionary rate at the root, rate variance and the level of rate smoothing between internal edges, are suggested to influence the results.

En este trabajo se ha estudiado el género Androcymbium (Colchicaceae) a dos niveles: macro- y micro- evolutivo. A nivel microevolutivo se ha obtenido que para las especies de Sudáfrica oriental la componente interpoblacional es muy importante para explicar la distribución de la variabilidad genética, igual que en Sudáfrica occidental. Para las especies de Namibia, la componente mas importante es la intrapoblacional, igual que en el norte de África. A nivel macroevolutivo se ha obtenido que el origen del género se sitúa en Sudáfrica occidental, datándose en 11,2&#61617;2 ma. Este género ha resultado ser parafilético, dada la aparición conjunta en un mismo clado de especies de Androcymbium y Colchicum, y las especies del norte de África derivan de un taxa de Namibia que llegó a la cuenca Mediterránea a principios del Plioceno gracias a la formación de un corredor árido entre las zonas áridas del suroeste y este de África. / In this study the genus Androcymbium (Colchicaceae) has been studied at two levels: macro- and micro- evolutive. At the microevolutive level it has been obtained that in the western south African species, the inter-populational component is very important to explain the distribution of the genetic variability, the same case like in western South Africa. In the Namibian species, the main component in the intra-populational, the same case as in north Africa. At the macroevolutive level it has obtained that the origin of the genus is located in western South Africa and it has been dated in 12.2&#61617;2 mya. This genus is paraphyletic because of the inclusion of some species of Colchicum within Androcymbium, and the origin of the northern Africa taxa are related with a Namibian taxa that colonized the Mediterranean basin at the beginning of Pliocene thanks to the formation of an arid corridor between the arid areas of south-western and eastern Africa.

Molecular dating (or molecular clock) is a powerful technique that uses the mutation rate of biomolecules to estimate divergence times among organisms. In the last two decades, the theory behind the molecular clock has been intensively developed, and it is now possible to employ sophisticated evolutionary models on genome-scaled datasets in a Bayesian framework. The molecular clock has been successfully applied to virtually all types of organisms and molecules to estimate timing of speciation, timing of gene duplications, and generation times: this knowledge allows contextualizing past and present events in the light of (paleo)ecological scenarios. Molecular clock studies are routinely used in evolutionary and ecological studies, but their use in applied fields such as agricultural and medical entomology is still scarce in particular because of a paucity of genome data. Genome-scaled clocks have been successfully applied, for example, to various model organisms such as Anopheles and Drosophila, as well as to invasive mosquitoes Aedes aegypti and Aedes albopictus. Many other invasive pests are emerging worldwide aided by global trade, increased connectivity among countries, lack of prevention, and flawed invasive species management. Among them, there is Aedes koreicus and Aedes japonicus, two invasive mosquito species which are monitored for public health concerns because of their harboured human pathogenic viruses. For these, as well as for other insects of societal relevance, such as the parasitoid Trissolcus japonicus, there is a paucity of gene markers and no genome data for large scale molecular clock studies. Invasive pests are typically studied using microevolutionary approaches that tackle events at an intraspecific level: these approaches provide important information for the pest management, for example, by revealing invasion routes and insecticide resistances. Approaches that tackle the deep-time evolution of the pest, such as the molecular clock, are instead less used in pest science. Many important traits associated with invasiveness have evolved by speciation over a long time frame: the molecular clock can reveal the paleo-ecological conditions that favoured these traits helping a better understanding of pest biology. Molecular clock, when coupled with phylogenomics, can further identify genes and patterns that characterize the pest: this knowledge can be used to enhance management practices. Although this is a data-driven thesis, its major aim is to provide new results to demonstrate the utility of the molecular clock in pest science. This has been done by systematically apply the molecular clock to various neglected organisms of medical and agricultural relevance. To this aim, I generated new genome data and/or assembled the largest genome-scaled data to date. I studied the molecular clock in mosquitoes, focusing on the Aedini radiation (Chapter 2) and identified a strong incongruence between the mitochondrial and nuclear phylogeny for what concerns their molecular clock. This result highlighted the importance of employing genome scaled data for these species to exclude stochastic effects due to poor/inaccurate sampling in clock studies. To tackle the absence of data, I further assembled the whole mitogenome of emerging invasive species Aedes koreicus and Aedes japonicus with the aim of producing useful data for molecular typing and of inferring divergence estimates using whole mitogenomes (Chapter 3). Dated phylogenies point toward more recent diversification of Aedini and Culicini compared to estimates from previous works, addressing the issue of taxon sampling sensitivity in dated phylogeny. Although it is possible to perform molecular clock studies on single/few gene markers, the current trend is to couple this methodology with genome-scaled datasets to reduce the stochastic effect of using few genes. For this reason, I sequenced the draft genome of A. koreicus and A. japonicus (Chapter 4). The assemblies were extremely fragmented, highlighting the problem of sequencing large genomes using short reads. The assemblies provided, however enough information for genome skimming allowing extraction of BUSCO genes for downstream analyses, whole mitogenome assemblies (used in Chapter 3), and characterisation of the associated metagenome. These data need to be integrated by long reads; it provides, however a first framework to investigate the genome evolution of these species. I further sequenced and assembled the genome of Trissolcus japonicus, the parasitoid wasp of the invasive pest Halyomorpha halys. To elucidate its divergence, estimate and define an intraspecific typing system to differentiate strains for biocontrol strategies, I reconstructed the mitochondrial genomes of two populations: the mitogenomes were surprisingly identical, suggesting that they belong to the same de facto population. I further provide a detailed clock investigation of Zika, a virus harboured and transmitted by some Aedes species (Chapter 5). Using the largest set of genomes to date, I could set the origin of ZIKV in the middle age and its first diversification in the mid-19th century. From a methodological point of view, the clocking of this virus highlighted the importance of checking for recombination and for cell-passages to obtain correct divergence estimates. I finally show my contributions to molecular clock studies of three other invasive species (Chapter 6): I helped disentangle the divergence times of Bactrocera, a genus of invasive fruit files pest of agriculture; I contributed in performing a phylogenomics study of opsin genes in Diptera; I used chloroplast and nuclear genome data to reconstruct the divergences of the invasive reed Arundo. In the various Chapters of my thesis, I highlighted the limits and the problems of current molecular clock methodologies and identified the best practices for different types of organisms in order to develop a cross-discipline understanding of the molecular clock techniques. The various results presented in this thesis further demonstrate the utility of the molecular clock approach in pest studies.

Das tropische Südostasien, und besonders der Indo-Australische Archipel, ist bekannt für seine bemerkenswerte floristische und faunistische Diversität, besonders konzentriert in vier der identifizierten Biodiversitäts-Hotspots (Indochina, Sundaland, die Philippinen und Wallacea). In dieser Arbeit wird die biogeographische Geschichte Südostasiens beleuchtet, um Regionen mit einer erhöhten Biodiversität zu identifizieren und zu testen, ob dies mit Diversifikationen innerhalb der Region und Einwanderungen und/oder Auswanderungen korreliert und ob sich diese Faktoren über die Zeit hinweg ausgleichen. Ein besonderer Augenmerk wird auf Sulawesi und seine besondere Fauna gelegt, um zu testen, ob ein Ursprung durch Vikarianz für verschiedene Tiergruppen plausibel erscheint und wann Diversifikationen innerhalb der Fisch- und Schnecken-Radiationen im Malili-Seensystem begannen. Dabei wird auf Meta-Analysen und mehrere Disziplinen zurückgegriffen für eine integrative biogeographische Geschichte Südoastasiens und seiner Fauna, indem molekulare Uhr-Analysen, Berechnungen zur Ermittlung des Ursprungsortes mit tektonischen, paläogeographischen und klimatischen Rekonstruktionen verbunden werden, um potentielle Ursachen für die heutige Verbreitung zu finden. / Tropical Southeast Asia, and particularly the Indo-Australian Archipelago, is known for its tremendous floral and faunal biodiversity, mainly accumulated in four of the world’s biodiversity hotspots identified (Indochina, Sundaland, the Philippines, and Wallacea). Here, Southeast Asia’s biogeographic history is examined to identify areas being characterized by high levels of biodiversity (number of lineages, species richness) through time and to test whether the respective biota is mainly due to in situ diversification, immigration and/or emigration, or equilibrium dynamics. Moreover, this thesis focuses particularly on Sulawesi and its peculiar fauna to test if a vicariant origin appears plausible for certain groups and when the remarkable fish and snail radiations found in the Malili Lakes system started to diversify. To achieve this, meta-analytical and multi-disciplinary approaches are considered for an integrative historical biogeographic history of Southeast Asia and its biota by using molecular clock analyses and ancestral area estimations together with tectonic, palaeogeographic and climatic reconstructions to reveal potential causes for present-day distribution.

La donnée de séquences nucléotidiques permet d'inférer des arbres phylogénétiques, ou phylogénies, qui décrivent leur lien de parenté au cours de l'évolution. Associer à ces séquences leur date de prélèvement ou leur pays de collecte, permet d'inférer la localisation temporelle ou spatiale de leurs ancêtres communs. Ces données et procédures sont très utilisées pour les séquences de virus et, notamment, celles du virus de l'immunodéficience humaine (VIH), afin d'en retracer l'histoire épidémique à la surface du globe et au cours du temps. L'utilisation de séquences échantillonnées à des moments différents (ou hétérochrones) sert aussi à estimer leur taux de substitution, qui caractérise la vitesse à laquelle elles évoluent.Les méthodes les plus couramment utilisées pour ces différentes tâches sont précises, mais lourdes en temps de calcul car basées sur des modèles complexes, et ne peuvent traiter que quelques centaines de séquences. Devant le nombre croissant de séquences disponibles dans les bases de données, souvent plusieurs milliers pour une étude donnée, le développement de méthodes rapides et efficaces devient indispensable. Nous présentons une méthode de distances, Ultrametric Least Squares, basée sur le principe des moindres carrés, souvent utilisé en phylogénie, qui permet d'estimer le taux de substitution d'un ensemble de séquences hétérochrones, dont on déduit ensuite facilement les dates des spéciations ancestrales. Nous montrons que le critère à optimiser est parabolique par morceaux et proposons un algorithme efficace pour trouver l'optimum global.L'utilisation de séquences échantillonnées en des lieux différents permet aussi de retracer les chaînes de transmission d'une épidémie. Dans ce cadre, nous utilisons la totalité des séquences disponibles (~3 500) du sous-type C du VIH-1 (VIH de type 1), responsable de près de 50% des infections mondiales au VIH-1, pour estimer ses principaux flux migratoires à l'échelle mondiale, ainsi que son origine géographique. Des outils novateurs, basés sur le principe de parcimonie combiné avec différents critères statistiques, sont utilisés afin de synthétiser et interpréter l'information contenue dans une grande phylogénie représentant l'ensemble des séquences étudiées. Enfin, l'origine géographique et temporelle de ce variant (VIH-1 C) au Sénégal est précisément explorée lors d'une seconde étude, portant notamment sur les hommes ayant des rapports sexuels avec des hommes. / Nucleotide sequences data enable the inference of phylogenetic trees, or phylogenies, describing their evolutionary re-lationships during evolution. Combining these sequences with their sampling date or country of origin, allows inferring the temporal or spatial localization of their common ancestors. These data and methods are widely used with viral sequences, and particularly with human immunodeficiency virus (HIV), to trace the viral epidemic history over time and throughout the globe. Using sequences sampled at different points in time (or heterochronous) is also a mean to estimate their substitution rate, which characterizes the speed of evolution. The most commonly used methods to achieve these tasks are accurate, but are computationally heavy since they are based on complex models, and can only handle few hundreds of sequences. With an increasing number of sequences avail-able in the databases, often several thousand for a given study, the development of fast and accurate methods becomes essential. Here, we present a new distance-based method, named Ultrametric Least Squares, which is based on the princi-ple of least squares (very popular in phylogenetics) to estimate the substitution rate of a set of heterochronous sequences and the dates of their most recent common ancestors. We demonstrate that the criterion to be optimized is piecewise parabolic, and provide an efficient algorithm to find the global minimum.Using sequences sampled at different locations also helps to trace transmission chains of an epidemic. In this respect, we used all available sequences (~3,500) of HIV-1 subtype C, responsible for nearly 50% of global HIV-1 infections, to estimate its major migratory flows on a worldwide scale and its geographic origin. Innovative tools, based on the principle of parsimony, combined with several statistical criteria were used to synthesize and interpret information in a large phylogeny representing all the studied sequences. Finally, the temporal and geographical origins of the HIV-1 subtype C in Senegal were further explored and more specifically for men who have sex with men.

Made available in DSpace on 2016-06-02T20:20:30Z (GMT). No. of bitstreams: 1 3078.pdf: 3949929 bytes, checksum: 0375aaec7134412a51147cc0d80c7620 (MD5) Previous issue date: 2010-05-21 / The State of Maranhão is considered as a transitional area between northeastern semiarid and amazonian rainforest. Various perennial rivers such as the rivers Parnaíba, Itapecuru, Mearim, Pindaré and Gurupi are found in Maranhão. Distribution patterns analysis indicated the region as an endemism area for Neotropical freshwater fishes. However, only few studies have been performed in the region. Therefore the relationships between the hidrographic set and the respective neighbour areas are not fully comprehended. One complication is the insufficient cientific knowledge about the endemism level in the region due to insufficient establishment of taxonomic bounds for several species in the area. This study examines the hypothesis that freshwater fishes from Maranhão rivers are valid taxonomic unities, and whether its hydrographic set can be considered as an endemism area for Neotropical fishes. The study is focused on the analsis of genetic differentiation of Hoplias malabaricus and Prochilodus lacustris. The geographic variation of H. malabaricus was studied using sequences of the DNAmt control region as well by geometric morphometrics. Besides the mitochondrial marker, the variation analyses of P. lacustris employed sequences of the S7 intron 1. Both species exhibited high genetic variability which may be related to its own ecological features. The genetic diversity of H. malabaricus, a sedentary species, is influenced by drainage architeture. On the other hand, the migratory behavior of P. lacustris and the results obtained had suggested that the variability found was influenced by historical factors. Because the most resolution of the P. lacustris data, the molecular clock hypothesis was tested and divergence times between populations sampled were estimated. These estimates matching with geological informations enabled us to identify several putative events that may play an important role in differentiation of the maranhense ichthyofauna. Under the taxonomic point of view, the hypothesis that H. malabaricus is a species complex was reinforced and the analyses suggested that putative criptic species occur in the region. The P. lacustris specimens constitute a taxonomic unit, but did not support the hypothesis that the species is endemic for the Parnaíba and Mearim rivers. Considering these results, we suggest that the most closely indication of endemism areas could be the ecoregions established by Secretaria de Recursos Hídricos from Ministério do Meio Ambiente. / O Estado do Maranhão é geralmente considerado uma área de transição entre o semiárido nordestino e a floresta amazônica, onde está localizado um conjunto de rios perenes, tais como, Parnaíba, Itapecuru, Mearim, Pindaré e Gurupi. Análises baseadas em padrões de distribuição têm indicado que a região constitui uma área de endemismo para peixes neotropicais. No entanto, devido ao reduzido número de estudos, as interrelações desse conjunto hidrográfico com áreas vizinhas são pouco compreendidas. Uma das dificuldades que surge do esquálido conhecimento científico é a identificação do nível de endemismo que a região abriga, uma vez que há problemas na definição dos limites taxonômicos de várias espécies com ocorrência registrada na área. Assim, este trabalho teve como objetivo testar as hipóteses de que as espécies de peixes dos rios do Maranhão são unidades taxonômicas válidas e, consequentemente, o conjunto hidrográfico pode ser considerado uma área de endemismo. O estudo foi centrado na análise de diversidade genética das espécies Hoplias malabaricus e Prochilodus lacustris. Em H. malabaricus a variação geográfica foi estudada usando sequências da região controle do DNAmt e através de morfometria geométrica. Além do marcador mitocondrial, na análise da variação em P. lacustris foram utilizadas sequências do íntron 1 do gene S7. Ambas as espécies apresentaram alta variabilidade genética que parece estar associada às características ecológicas de cada uma. H. malabaricus, sendo sedentária, teve sua diversidade genética influenciada por arquitetura de drenagem. Por outro lado, dado o comportamento migratório de P. lacustris, os resultados sugeriram que a variabilidade observada foi influenciada por fatores históricos. A maior resolução dos dados em P. lacustris permitiu testar a hipótese de relógio molecular e estimar tempos de divergências entre as populações amostradas. Estas estimativas foram combinadas com informações geológicas disponíveis, possibilitando a identificação de vários eventos que provavelmente exerceram papéis importantes na diferenciação da ictiofauna maranhense. Do ponto de vista taxonômico, as análises reforçaram a hipótese de que H. malabaricus é um complexo de espécie, sugerindo a possibilidade de ocorrência de espécies crípticas na área. As amostras de P. lacustris, por sua vez, constituem uma unidade taxonômica, mas não são consistentes com a hipótese de que a espécie é endêmica para os rios Parnaíba e Mearim. Diante dos resultados obtidos, sugerimos que a indicação mais aproximada de áreas de endemismo seja a de ecorregiões definidas pela Secretaria de Recursos Hídricos do Ministério do Meio Ambiente.

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