Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os fatores que explicam a distribuição observada em plantas e animais é uma pergunta que intriga naturalistas, biogeógrafos e ecólogos há mais de um século. Ainda nos primórdios da disciplina de ecologia, as tolerâncias ambientais já haviam sido apontadas como as grandes responsáveis pelo padrão observado da distribuição dos seres vivos, o que mais tarde levou à concepção de nicho ecológico das espécies. Nos últimos anos, o estudo das distribuições dos organismos ganhou grande impulso e destaque na literatura. O motivo foi a maior disponibilidade de catálogos de presença de espécies, o desenvolvimento de bancos de variáveis ambientais de todo o planeta e de ferramentas computacionais capazes de projetar mapas de distribuição potencial de um dado organismo. Estes instrumentos, coletivamente chamados de Modelos de Distribuição de Espécies (MDEs) têm sido desde então amplamente utilizados em estudos de diferentes escopos. Um deles é a avaliação de potenciais áreas suscetíveis à invasão de organismos exóticos. Este estudo tem, portanto, o objetivo de compreender, através de MDEs, os fatores subjacentes à distribuição de duas espécies de corais escleractíneos invasores nativos do Oceano Pacífico e ambas invasoras bem sucedidas de diversas partes do Oceano Atlântico, destacadamente o litoral fluminense. Os resultados mostraram que os modelos preditivos da espécie Tubastraea coccinea (LESSON, 1829), cosmopolita amplamente difundida na sua região nativa pelo Indo- Pacífico demonstraram de maneira satisfatória suas áreas de distribuição nas áreas invadidas do Atlântico. Sua distribuição está basicamente associada a regiões com alta disponibilidade de calcita e baixa produtividade fitoplanctônica. Por outro lado, a aplicação de MDEs foi incapaz de predizer a distribuição de T. tagusensis (WELLS,1982) no Atlântico. Essta espécie, ao contrário de sua congênere, tem distribuição bastante restrita em sua região nativa, o arquipélago de Galápagos. Através de análises posteriores foi possível constatar a mudança no nicho observado durante o processo de invasão. Finalmente, o sucesso preditivo para T. coccinea e o fracasso dos modelos para T. tagusensis levantam importantes questões sobre quais os aspectos ecológicos das espécies são mais favoráveis à aplicação de MDEs. Adicionalmente, lança importantes ressalvas na utilização recentemente tão difundida destas ferramentas como forma de previsão de invasões biológicas e em estudos de efeitos de alterações climáticas sobre a distribuição das espécies. / The factors underpinning the observed distribution of plants and animals across time and space are a central question in ecology and has intrigued scientists for over a century. But even back on those early times, the role of climatic tolerances of the species were recognized as one of the main explanations for such distributional patterns. Later, these assumptions gave rise to the concept of niche which triggered several advances in the study of natural history. Recently, these studies were addressed in the light of novel computational techniques capable of providing potential distributional maps for a given species, generically called Species Distribution Models (SDMs). This coupled with the broader availability of species occurrence records and of environmental data from international databases made studies with SDMs very popular and ubiquitous in the literature. One of the main uses of the SDMs approach is the assessment of potentially susceptible areas of invasion by non- indigenous species. Therefore, here we used SDMs to better understand the major factors related to the current distribution of two well established invasive scleractinian coral species in the Atlantic, both from the Pacific Ocean. The results showed that the models were successful in predicting the potentially invaded sites by the cosmopolitan Tubastraea coccinea (LESSON, 1829), broadly distributed throughout the Pacific. This species distribution was basically associated with increasing concentrations of calcite and lower levels of phytoplankton activity. However, the models were incapable of predicting the survival and establishment of T. tagusensis (WELLS, 1982) in the Atlantic. This species, unlike its congener, has a very restricted distribution in its native regions, the Galapagos Islands. A posterior analyzes indeed showed a niche shift during the invasion event of T. tagusensis in the Atlantic. Finally, the good modelling results for T. coccinea contrasted with the failure of modelling T. tagusensis invasion highlight important explanations on methodological procedures in SDMs. It also helps to better understand which ecological aspects of the species are favourable toward good modelling performance. In addition to that, these results calls for precaution when analyzing SDMs results, particularly in invasion and climate change scenarios studies.

Distintos padrões de composição de espécies de plantas podem ser observados ao longo de metacomunidades, pois espécies variam de acordo com os diferentes tipos de ambiente e também com a distância geográfica, dado o processo de dispersão. Ainda, estes mecanismos podem causar variação temporal na composição ou abundância de espécies em um sítio devido a alterações que estes mecanismos podem sofrer. Compreender como as mudanças na composição de espécies no espaço, definida como beta diversidade, ou no tempo estão relacionadas ao clima passado, atual ou futuro podem ajudar no planejamento de conservação de uma região. Assim, esta tese esta dividida em quatro capítulos e aborda questões relacionadas com mudanças espaçotemporais na composição de espécies sob uma perspectiva de planejamento de conservação e mudanças climáticas na Mata Atlântica. O primeiro capítulo apresenta um banco de dados com a informação de ocorrência de 1917 espécies de plantas arbóreas distribuídas em 206 comunidades na Mata Atlântica, em diferentes formações florestais (Floresta Atlântica stricto sensu (s.s.), Floresta com Araucária e Floresta Estacional). O segundo capítulo relacionou padrões de beta diversidade com a efetividade da rede de áreas protegidas nas formações florestais do sul da Mata Atlântica (Floresta Atlântica, Floresta com Araucária e Floresta Estacional). Encontramos altos valores de turnover e baixo aninhamento para todas as formações florestais, por isso recomendamos que esforços adicionais precisam almejar o aumento no número de áreas protegidas, especialmente para a Floresta com Araucária e a Floresta Estacional. A maioria das áreas protegidas no sul da Mata Atlântica estão concentradas na região leste, priorizando a Floresta Atlântica s.s. O terceiro capítulo trouxe novas perspectivas sobre a dinâmica da Floresta com Araucária no tempo através da modelagem de nicho ecológica. Durante as flutuações climáticas do Quaternário, estudos palinológicos indicavam uma expansão da Floresta com Araucária, porém nossos resultados demonstraram uma retração da área de cobertura desta floresta, principalmente nas zonas de contato com outras formações florestais. Também observamos que futuramente, se a temperatura continuar aumentando como previsto, a Floresta com Araucária sofrerá uma drástica redução na sua distribuição. Por fim, o capítulo quatro investigou como as espécies de árvores estão respondendo aos efeitos de mudanças climáticas em parcelas permanentes localizadas em ecótonos de florestas Atlânticas. Os resultados mostram que espécies tropicais estão migrando em direção a áreas de maior altitude, ou seja mais frias. Espécies tropicais que já ocorrem em áreas vi de Floresta com Araucária estão apresentando maiores taxas de recrutamento e crescimento, e menor mortalidade do que espécies temperadas, características da Floresta com Araucária. / Distinct patterns of plant species composition can be observed along metacommunities, as species vary in relation to different types of environment and also to the geographic distance, given the dispersal process. These mechanisms may yet lead temporal variation in species composition or abundance in a given place due to fluctuations on these mechanisms. Understanding how changes in species composition across the space, defined as beta diversity, or in time are related with past, current and future climate changes can help conservation planning in a given region. Thus, this thesis is divided into four chapters and discusses shifts in species composition across space and time under the perspective of conservation planning and climate changes in the Atlantic Forest. The first chapter shows a database with 1917 tree species occurrence distributed in 206 sites across distinct forest formations in the Atlantic Forest biome (Atlantic Rainforest, Araucaria Forest and Seasonal Forest). The second chapter related beta diversity patterns with the effectiveness of the current network of protected areas in southern Brazilian Atlantic forests (Atlantic Rainforest, Araucaria Forest and Seasonal Forest). We found high values of turnover and low nestedness for all forest formations, thus additional conservation efforts must target an increase in the number of protected areas, especially for the Araucaria Forest and the Seasonal Forest. Most protected areas are currently limited to the eastern region and prioritize the Atlantic Rainforest. The third chapter brought new insights about the Araucaria Forest dynamics in time through ecological niche models. During the climatic fluctuations of the Quaternary, palynological studies indicated an expansion of the Araucaria Forest, however our results demonstrated an overall retraction of the cover area, mainly in boundary zones with other forest formations. Yet, we showed that in the future, if the temperature continues to increase as expected, the Araucaria Forest would suffer a drastic reduction in its distribution. Finally, the fourth chapter investigated how tree species are responding to climatic changes in permanent plots located in Atlantic forests ecotones. Our results showed that tropical species are migrating towards to colder areas in higher altitudes. Tropical species that already occur in Araucaria Forest areas are even presenting higher rates of recruitment and growth, and lower mortality than temperate species characteristics from the Araucaria Forest.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-11-20T11:01:42Z No. of bitstreams: 2 Tese - Rodrigo Antônio de Souza - 2013.pdf: 7884679 bytes, checksum: 3f46d66ae21c1c1457e06e8ab1841fc2 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2014-11-20T11:02:17Z (GMT) No. of bitstreams: 2 Tese - Rodrigo Antônio de Souza - 2013.pdf: 7884679 bytes, checksum: 3f46d66ae21c1c1457e06e8ab1841fc2 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-11-20T11:02:17Z (GMT). No. of bitstreams: 2 Tese - Rodrigo Antônio de Souza - 2013.pdf: 7884679 bytes, checksum: 3f46d66ae21c1c1457e06e8ab1841fc2 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-02-18 / The Amazon forest is being cleared, burned, fragmented and over-exploited at unprecedented scales. As important as the punishment for environmental crimes, it is the prevention. This requires the identification of deforestation facilitators and deforestation mitigators, beyond the knowledge of where the combination of these factors makes it more likely the occurrence of deforestation. If there is a combination of conditions that increase the deforestation probability in a particular area, it is possible estimate potential areas of new deforestation using Ecological Niche Modeling (ENM). The main objective of this study is to test the efficiency of ENMs to define potential areas of deforestation in the Brazilian Amazon. In the last chapters, we raise the factors relevant to the current deforestation and that can be inputs for modeling. For this, we test the relationship between size of farms, government custody areas, agricultural technification and law enforcements with deforestation. In later chapters we use ENMs, first considering an area in western Brazilian Amazon and comparing with other models established in the literature. Subsequently, we consider the entire Brazilian Amazon and check the ENM efficiency along the deforestation frontier gradient of the municipalities. Potential areas created from the ENM, demonstrated great effectiveness in predicting new areas of deforestation, especially in regions where forest loss is very active. Thus, we can to consider these models as a tool for action of command and control planning, reducing money costs and time. Moreover, we find that the presence of the governance in the Amazon region, either by government custody areas, or punitive actions, reduces deforestation. Deforestation continues to happen in large properties, however small farms deforest more than the law allows in its limits. The municipalities with obsolete agricultural practices are the most deforested. / A floresta Amazônica, vem sendo desmatada, queimada, fragmentada e sobre-explorada em escalas sem precedentes. Mais importante que à punição ao ilícito ambiental cometido, é a prevenção deste. Para isso é necessária a identificação dos facilitadores e dos mitigadores do desmatamento, além de conhecer os locais onde a combinação desses fatores torna mais propensa a ocorrência do desmate. Se existe um conjunto de condições que aumenta a probabilidade de desmatamento em determinada area, é possível estimar áreas potenciais de novos desmatamentos usando Modelagem Baseada em Nicho Ecológico (ENM). O principal objetivo desse trabalho é testar a eficiência de ENMs para a definição de áreas potenciais de desmatamento na Amazônia brasileira. Nos primeiros capítulos, levantamos os fatores relevantes para o desmatamento atual e que podem ser insumos para criação de modelos. Para isso, testamos as relações entre tamanho de propriedades rurais, áreas tuteladas pelo estado, tecnificação agrícola e esforços de reeprensão, com o desmatamento. Nos últimos capítulos usamos ENMs, primeiramente considerando uma área na Amazônia ocidental brasileira e comparando com outros modelos consolidados na literatura. Posteriormente, consideramos toda Amazônia Brasileira e verificamos a eficiência dos ENMs nos munícipios amazônicos ao longo do gradiente de pré-fronteira, fronteira, pós-fronteira de desmatamento.. As áreas potenciais criadas a partir do ENM, demonstraram grande efetividade na predição de novas áreas de desmatamento, principalmente nas regiões onde a perda de floresta é mais ativa. Assim, podemos considerar esses modelos ferramentas no planejamento de ações de controle e comando contra o desmatamento, diminuindo custos e tempo. Além disso encontramos que a presença do estado na região Amazônica, seja por áreas tuteladas pelo estado, ou ações punitivas, diminui o desmatamento. O desmatamento continua acontecendo em grandes propriedades, entretanto as pequenas propriedades desmatam mais do que a lei permite em seus limites. Os municípios que apresentam as práticas agrícolas mais obsoletas são os que mais desmatam .

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-09-09T13:51:21Z No. of bitstreams: 2 Tese - Edivaldo Barbosa de Almeida Júnior - 2015.pdf: 11899635 bytes, checksum: 81eb843ad44f05464a9ded05612db917 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-09-09T13:51:52Z (GMT) No. of bitstreams: 2 Tese - Edivaldo Barbosa de Almeida Júnior - 2015.pdf: 11899635 bytes, checksum: 81eb843ad44f05464a9ded05612db917 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-09-09T13:51:52Z (GMT). No. of bitstreams: 2 Tese - Edivaldo Barbosa de Almeida Júnior - 2015.pdf: 11899635 bytes, checksum: 81eb843ad44f05464a9ded05612db917 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-12-21 / The Annona crassiflora Mart. species (Annonaceae) is a fruit plant native from Cerrado, widely distributed throughout the biome. The goal here was evaluate the spatial distribution of genetic variability in natural subpopulations of the species, geographically, and relate the genetic diversity levels with climatic and landscape profile, furthermore the pollen dispersal within a subpopulation. We used here six pair of microsatellite primers. To evaluate thedistribution of genetic variability we sampled 25 natural subpopulations, 30.6 plants per subpopulation, on average. We estimate the genetic diversity (He), allelic richness (Ar), fixation index (f), genetic structure, using coancestry coefficient (θ) and inbreeding coefficient of overall population (F). The spatial pattern the genetic variability was evaluated by Mantel test, Moran's I index and linear regression of genetic parameter with two spatial dimensions (latitude and longitude). We correlate He, Ar and f with climate suitability and the percentage of Cerrado vegetation around subpopulations. Furthermore we evaluated the pollen dispersal by paternity analysis, using 572 plants, including 460 seeds, 20 mother plants and 92 pollen donors candidate, within a natural subpopulation. The outcrossing rates were also evaluated in maternal families using the mixed mating model. The outcrossing rates indicate mating system with prevalence of allogamy. The assignment of paternity indicated that gene flow mainly occurs in short distances, until 360 meters, in the subpopulation evaluated. The 25 subpopulations have moderate genetic diversity levels and strong genetic structure. We found inbreeding due to the subdivision, but not in mating within subpopulations. The demes belongs to two consistent groups with genetic discontinuity between the northwest and southeast subpopulations distribution. The genetic diversity and allelic richness showed strong relationship with longitude, suggesting a range expansion in the southeastern direction. We noted that spatial distribution of genetic diversity and allelic richness are related to suitability at the last glacial maximum, by an indirect effect of geographical distances, whereas no relationship was observed regarding present suitability. The percentage of cover natural vegetation, in turn not explain the spatial distribution of genetic diversity, allelic richness and inbreeding coefficient. / A espécie Annona crassiflora Mart. (Annonaceae) é uma planta frutífera nativa do Cerrado, amplamente distribuída ao longo do Bioma. O objetivo do trabalho foi avaliar a distribuição espacial da variabilidade genética em subpopulações naturais da espécie, em um contexto geográfico e relacionar os níveis de diversidade observados com variáveis climáticas e da paisagem, além da distância de dispersão de pólen em escala local, em uma subpopulação natural. No presente estudo foram empregados seis pares de iniciadores microssatélites. Para avaliar a distribuição da variabilidade genética foram amostradas 25 subpopulações naturais, em média 30,6 plantas por subpopulação. Foram estimados os níveis de diversidade genética (He), riqueza alélica (Ar), índice de fixação intrapopulacional (f), estrutura genética, por meio do coeficiente de coancestria (θ) e coeficiente de endogamia da população total (F). O padrão espacial da variabilidade genética foi avaliado por meio do Teste de Mantel, I de Moran e regressão linear dos parâmetros genéticos com as duas dimensões espaciais (latitude e longitude). As estimativas de He, Ar e f foram relacionadas com métricas de adequabilidade climática e com a porcentagem de remanescentes de vegetação do Cerrado. A dispersão de pólen foi avaliada por meio de análise de atribuição de paternidade usando 572 plantas, que incluem 460 semente, 20 plantas matrizes e 92 candidatos a doadores de pólen, em uma subpopulação natural da espécie. As taxas de fecundação cruzada também foram avaliadas, nas famílias maternas, usando o modelo misto de reprodução. As taxas de cruzamento indicam sistema reprodutivo com prevalência de alogamia. A atribuição de paternidade indicou que o fluxo gênico ocorre, prioritariamente, em curtas distâncias, em até 360 metros, na subpopulação avaliada. As 25 subpopulações apresentam níveis elevados de diversidade e forte estruturação genética. Há endogamia devido à subdivisão, mas não em relação ao sistema de cruzamento. Os demes formaram dois grupos consistentes, com descontinuidade genética entre as subpopulações do noroeste e sudeste da distribuição. A diversidade genética e a riqueza alélica mostraram forte relação com a longitude, sugerindo uma expansão da distribuição na direção sudeste. Foi observado que a distribuição espacial da diversidade genética e riqueza alélica estão relacionadas com a adequabilidade climática no último máximo glacial, por um efeito indireto do espaço geográfico, enquanto que nenhuma relação foi observada com a adequabilidade no presente. A porcentagem de remanescentes da vegetação natural, por sua vez não explicou a distribuição espacial da diversidade genética, riqueza alélica e coeficiente de endogamia.

Ecological niche modelling is a method designed to describe and predict the geographic distribution of an organism. This procedure aims to quantify the species-environment relationship by describing the association between the organism’s occurrence records and the environmental characteristics at these points. More simply, these models attempt to capture the ecological niche that a particular organism occupies. A popular application of ecological niche models is to predict the potential distribution of invasive alien species in their introduced range. From a biodiversity conservation perspective, a pro-active approach to the management of invasions would be to predict the potential distribution of the species so that areas susceptible to invasion can be identified. The performance of ecological niche models and the accuracy of the potential range predictions depend on the quality of the data that is used to calibrate and evaluate the models. Three different types of input data can be used to calibrate models when producing potential distribution predictions in the introduced range of an invasive alien species. Models can be calibrated with native range occurrence records, introduced range occurrence records or a combination of records from both ranges. However, native range occurrence records might suffer from geographical bias as a result of biased sampling or incomplete sampling. When occurrence records are geographically biased, the underlying environmental gradients in which a species can persist are unlikely to be fully sampled, which could result in an underestimation of the potential distribution of the species in the introduced range. I investigated the impact of geographical bias in native range occurrence records on the performance of ecological niche models for 19 invasive plant species by simulating two geographical bias scenarios (six different treatments) in the native range occurrence records of the species. The geographical bias simulated in this study was sufficient to result in significant environmental bias across treatments, but despite this I did not find a significant effect on model performance. However, this finding was perhaps influenced by the quality of the testing dataset and therefore one should be wary of the possible effects of geographical bias when calibrating models with native range occurrence records or combinations there of. Secondly, models can be calibrated with records obtained from the introduced range of a species. However, when calibrating models with records from the introduced range, uncertainties in terms of the equilibrium status and introduction history could influence data quality and thus model performance. A species that has recently been introduced to a new region is unlikely to be in equilibrium with the environment as insufficient time will have elapsed to allow it to disperse to suitable areas, therefore the occurrence records available would be unlikely to capture its full environmental niche and therefore underestimate the species’ potential distribution. I compared model performance for seven invasive alien plant species with different simulated introduction histories when calibrated with native range records, introduced range records or a combination of records from both ranges. A single introduction, multiple introduction and well established scenario was simulated from the introduced range records available for a species. Model performance was not significantly different when compared between models that were calibrated with datasets representing these three types of input data under a simulated single introduction or multiple introduction scenario, indicating that these datasets probably described enough of the species environmental niche to be able to make accurate predictions. However, model performance was significantly different for models calibrated with introduced range records and a combination of records from both ranges under the well established scenario. Further research is recommended to fully understand the effects of introduction history on the niche of the species. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Zoology and Entomology / unrestricted

Le changement climatique et les invasions biologiques sont parmi les plus grandes menaces de la biodiversité et leurs impacts pourraient augmenter jusqu’à la fin du siècle. Parmi les espèces envahissantes, les fourmis sont un groupe particulièrement néfaste dû à leurs impacts sur les espèces natives, les processus écosystémique, la santé, l’agriculture et l’économie. L’objectif de cette thèse était de prédire les invasions de fourmis – en particulier avec le changement climatique qui pourrait favoriser les invasions en éliminant des barrières thermiques. J’ai utilisé trois approches complémentaires afin d’étudier le potentiel de différentes espèces à envahir : des modèles de distribution, des expériences comportementales et l’analyses d’une base de données de traits écologiques. J’ai modélisé l’aire favorable pour 15 espèces de fourmis parmi les pires, à la fois globalement, par continents, et dans les 34 hotspots de biodiversité. La distribution potentielle de seulement cinq espèce est prédite de diminuer (jusqu’à 35.8%) avec le changement climatique et l’aire potentielle diminue pour la plupart des espèces jusqu’à 63.2%. Les hotspots d’invasions de fourmis se situaient surtout dans des régions tropicales et subtropicales et ils correspondent particulièrement aux hotspots de biodiversité. Contrairement à ce qui est généralement admis, le changement climatique et les invasions biologiques n’agiront pas de manière synergique pour les fourmis. Par contre, les invasions de fourmis resteront probablement un problème global majeur, en particuliers dans les zones où les hotspots de biodiversité et les hotspots d’invasion se superposent. Les modèles de distribution ont identifié de larges zones de recouvrement entre aires favorables de plusieurs espèces de fourmis envahissantes. Dans le futur, ces espèces pourraient arriver simultanément dans les mêmes régions et entrer en compétition. Dans une série d’expériences, j’ai testé les différences comportementales entre 7 espèces de fourmis envahissantes (Anoplolepis gracilipes, Paratrechina longicornis, Myrmica rubra, Linepithema humile, Lasius neglectus, Wasmannia auropunctata et Pheidole megacephala). J’ai découvert deux stratégies comportementales différentes. Les interactions au niveau de la colonie ont suivi des processus démographiques plus complexes. De plus, j’ai mis au point deux expériences pour tester la capacité des fourmis envahissantes à explorer un nouvel espace et à exploiter des ressources. J’ai trouvé des différences significatives entre espèces et leur capacité à dominer par interférence comportementale était négativement corrélée à leurs capacités à découvrir et exploiter des ressources. Cette série d’expériences suggère que les ‘mécanismes’ d’invasion sont plus complexes que ce qui est généralement suggéré et que différentes espèces pourraient utiliser des stratégies comportementales différentes. Étant donné qu’il existe plus de 250 espèces de fourmis exotiques, il serait intéressant de pouvoir identifier à l’avance des futurs envahisseurs potentiels. Afin d’identifier des traits associés au caractère envahissant des fourmis, j’ai mis en place une base de données qui contient 2193 espèces de fourmis et 24 traits écologiques. J’ai effectué une analyse préliminaire de différences de traits entre fourmis natives et envahissantes qui a montré qu’il existe clairement des groupement distincts de natives et envahissantes, avec les espèces exotiques au milieu. Ces résultats pourraient servir de base pour construire un modèle prédictif des invasions de fourmis. Ces différentes approches (modèles, expériences, base de données) sont complémentaires car elles s’intéressent à des aspects différents du futur des invasions de fourmis qui sera vraisemblablement fortement influencé par le changement climatique. Le pires envahisseurs de demain ne seront probablement pas les même qu’aujourd’hui et les zones les plus à risque pourraient changer également. / Climate change and biological invasions are both among the greatest threats to biodiversity and their impacts might increase by the end of the century. Among invasive species, ants are a prominent group due to their negative impacts on native species, ecosystem processes, human and animal health, agro-ecosystems and the economy. The objective of this thesis was to forecast future ant invasions – especially in the light of on-going climate change, which is generally thought to favour invasive species by removing thermal barriers. I used three complementary approaches to study the potential of different ant species to invade in the future: species distribution modelling, behavioural experiments and the analysis of a database of ecological traits. I modelled suitable area for 15 of the worst invasive ant species, both currently and with predicted climate change, globally, regionally and within the world’s 34 biodiversity hotspots. Surprisingly, the potential distribution of only five species was predicted to increase (up to 35.8%) with climate change, with most declining by up to 63.3%. The ant invasion hotspots are predominantly in tropical and subtropical regions of South America, Africa, Asia and Oceanic islands, and particularly correspond with biodiversity hotspots. Contrary to general expectations, climate change and biological invasions will not systematically act synergistically for ants. In addition, I found that the impacts of climate change can change over time and even reverse the trend of the impact (i.e., an increase instead of a decrease or vice versa). However, ant invasions will likely remain as a major global problem, especially where invasion hotspots coincide with biodiversity hotspots. The species distribution models have identified large potentially overlapping distributions of several invasive ants. In the future, these species may arrive simultaneously in the same regions and compete with each other. In a series of experiments, I tested behavioural differences among 7 highly invasive ant species (Anoplolepis gracilipes, Paratrechina longicornis, Myrmica rubra, Linepithema humile, Lasius neglectus, Wasmannia auropunctata and Pheidole megacephala). I discovered two different behavioural strategies among invasive ants. Interactions at the colony level, exhibited more complex demographic processes and more variability. Further, I investigated resource competition and differences in resource exploitation. I found significant differences among species, with competitive abilities that were negatively correlated with behavioural dominance. This series of experiments suggests that the ‘mechanisms’ of invasiveness are more complex than previously thought and that different invasive ant species may use different behavioural strategies. Since there are more than 250 exotic species of ants, it would be interesting to identify potential future invaders. In order to identify traits associated with invasiveness in ants, I set up a database with 2193 ant species and 24 ecological characteristics. I performed a preliminary analysis of trait differences between native and invasive ants that shows clearly different clusters of invasive and native species, with exotic species in between. These results could be used as a basis to construct a predictive model of future ant invasions. The different methods used (models, experiments, database) are complementary in that they explore different aspects of the future ant invasions which are likely to be influenced by on-going climate change. The worst invaders of tomorrow may not be the same as today and similarly, areas most at risk are likely to change.