Metapopulation ecology has developed to explain the population dynamics that occur in spatially structured landscapes. In this study, I combined an empirical laboratory approach, using metapopulation microcosms of Callosobruchus maculatus and its endospecific parasitoid Anisopteromalus calandrae, with mathematical population models in order to investigate several fundamental metapopulation processes. Population dynamics in these systems can be studied at two scales; the local patch-wise scale and the regional metapopulation scale. Here I demonstrate that in both homogeneous and heterogeneous landscapes knowledge of local scale demographic processes is necessary in order to understand regional metapopulation dynamics. The differences in the rate and net direction of dispersal between patches as a result of the permeability of the matrix in homogeneous systems and density-dependent dispersal in heterogeneous systems were also explored. Metapopulation dynamics rely on a balance between local extinctions and recolonisations. Therefore, increasing local mortality rates is likely to be detrimental to the persistence of the system. Here, the impact of several common harvesting strategies on the persistence of a host-parasitoid metapopulation was examined. Contrary to expectation I discovered that harvesting in these systems increased both local and regional population sizes. The increased population size as a result of increased mortality was explained in terms of a hydra effect, where harvesting relaxed density-dependence acting on local host populations. The results presented in this thesis are relevant for the monitoring, management and conservation of natural metapopulations and the development of sustainable harvesting strategies in structured landscapes.

Ecological network theory has developed from studies of static, binary trophic relationships to the analysis of quantitative, dynamic communities consisting of multiple link-types. Particularly, work has focused on the dynamic nature of ecological networks, which maintains stability in complex communities. However, there are few in situ network-level studies of the determinants of temporal and spatial variation in community structure. This thesis utilises data from a 10-year study of a host-parasitoid network and a collaborative study in an applied ecological setting to identify individual level factors important to network structure. The work aims towards an empirical, predictive framework linking adaptive foraging behaviour to ecological network structure. The results show that condition-dependent foraging behaviours structure host-parasitoid networks. The realised niches of the studied parasitoid species were generally biased towards larger host species and condition-dependent sex ratio allocation increased the likelihood that females would eclose from relatively larger hosts and males from relatively smaller hosts, which resulted in sex ratios deviating from Hamiltonian (50:50) predictions. Further, both of these aspects of behaviour are plastic, where parasitoid behaviour responded to environmental heterogeneity. Particularly, host preference behaviour conformed to an egg-/time-limitation framework, where the size dependency of the behaviour is greater when individuals have a greater likelihood of being egg-limited. Both the size-dependency and the plasticity of these behaviours differed significantly between secondary parasitoid species. This species identity effect interacted with landscape heterogeneity, which may explain some inter- and intra-specific variation in network structure. With respect to applied ecology, the results show that the benefits of natural vegetation for pest control are dependent upon the dispersal capabilities and the diet breadth of the pest and its natural enemies. The findings are evaluated towards a predictive framework for understanding the effects of future climate change on community structure and stability. We consider this framework in terms of applied ecology, particularly pest control ecosystem services provided by natural vegetation in an agricultural environment. The synergistic nature of the multiple determinants of network structure found in this thesis suggest that future studies should focus on the whole network, which is not necessarily the sum of its parts.

Chenopodium album is considered one of the most important weeds adversely affecting agricultural production due to its highly competitive influence on field crops. Chemical herbicides have increased the efficiency of farming, but recently problems of herbicideresistant weed populations and herbicide residues in soil, water, food products and effects on non-target organisms have increased, consequently, other methods of control of weeds by using specific fungi as herbicides have been suggested. The purpose of this research was to evaluate the biological control of the weed Chenopodium album by the fungus Ascochyta caulina. Some of the factors which control dormancy and germination of Chenopodium album seeds have been investigated to understand better the weed population dynamics. The results showed that seeds from two populations (UK and Libya) differ in their response to factors such as light, chilling, and burying in soil. This could have implications for effective control of the weed in different regions. Two formulations of mycoherbicides (Tween 80 and Gelatine based applications) were tested in the laboratory, and showed promise in reducing growth of the weed, especially the formula of Tween 80. There was extensive shoot fresh and dry weight reduction of inoculated Chenopodium album, as well as reduced root growth. Highest disease severity rates were observed on plants in the first three week of life. A field trial revealed similar results but less disease severity was observed, possibly because of dry weather. However, it was concluded that the fungus Ascochyta caulina is a potentially useful biological control agent but many factors still can be modified in relation to application of the mycoherbicide to increase its efficacy.

La compétition par interférence et ses effets sur la dynamique des populations suscitent un intérêt croissant. La température a aussi un fort effet sur la physiologie et les comportements individuels ainsi que sur les dynamiques des populations. Face au changement climatique, comprendre les interactions compétition-température-dynamique des populations est un enjeu majeur en biologie des populations. Les interactions entre individus sont liées à leur taille corporelle. La structure en taille de populations de deux clones du collembole Folsomia candida a été suivie pendant 2 à 4 ans à 4 températures. L'analyse des séries temporelles de leur structure à 21°C a révélé une dépendance de la dynamique aux conditions individuelles d¿accès à la ressource, liées aux plus grands individus. Nous avons modifié la structure de populations à 21°C et observé leur retour à l'équilibre, puis observé le comportement d'accès à la ressource. Cela a démontré le rôle des grands adultes dans la régulation des populations, en interférant avec les plus petits pour l'accès aux ressources. Grâce à un modèle de populations structurées intégrant l'interférence, nous avons montré que son intensité croissante cause : l'amortissement des cycles de générations, la survie de grands individus, des cycles induits par l'interférence. Nous avons enfin comparé les normes de réactions à la température sur des individus isolés et dans des populations afin de comprendre les interactions compétition-température dans la régulation des populations. Plusieurs niveaux de complexité permettent de comprendre l'effet des changements environnementaux sur les populations. / Interference competition and its effects on population dynamics are of growing interest. Temperature also plays an important role on the physiology and individual behavior as well as on population dynamics populations. In the context of climate change, understanding the effect of interactions between individuals on population dynamics and their interactions with temperature is an important issue for population biology. Interactions between individuals are related to their body size. The size structure of several populations of two clones of Collembola Folsomia candida was monitored for 2-4 years at four temperatures from 11 ° C to 26 ° C. The time series analysis of their structure at 21 ° C revealed a dependence of the dynamics on individual access to the resource related to the presence of large individuals. We then changed some population structures at 21 ° C and observed their return to equilibrium. We observed real-time access to the resource behavior. These studies have shown the role of large adults in population control by interfering with smaller individuals for access to resources. Through a structured model incorporating interference competition, we have shown that its intensity may have different effects on the dynamics of structured populations: damping single generation cycles, allowing the survival of large individuals, and causing interference induced cycles. Finally, we compared the reaction norms to temperature on isolated individuals and populations in order to understand the competition-temperature interactions in regulating populations. Several levels of complexity allow us to understand the effect of environmental change on populations

Les lombriciens remplissent, dans les agrosystèmes, de nombreux services, importants pour la production et le bon fonctionnement du sol. Cependant, on manque de connaissances sur la manière dont les facteurs jouent, au champ, sur la densité et la diversité spécifique. Cela rend difficile la prévision des effets des pratiques sur la macrofaune du sol et la mise au point de systèmes de culture en Agriculture Biologique, favorables aux populations de vers endogés.L'objectif de cette thèse était d'analyser, au champ, les variations au cours de l'année de l'abondance des lombriciens dans le contexte de l'Agriculture Biologique du Bassin Parisien. Nous nous sommes tout particulièrement interessés au cas des espèces endogées dont nous avons suivi les abondances dans 5 parcelles pendant 2 ans (2009 et 2010). L'analyse de ces données (et de la littérature scientifique) nous a amené à proposer un modèle simulant la dynamique des populations de vers de l'espèce la plus fréquemment rencontrée sur ces parcelles, A. Caliginosa. Ce modèle est basé sur celui de C. Pelosi (Pelosi et al., 2008).L'analyse des données de suivi des populations a montré qu'il existait un schéma général décrivant l'évolution annuelle de l'abondance (i.e. la densité de vers endogés actifs dans la couche 0-30 cm) de ces parcelles labourées et cultivées en céréales. Ce schéma général est caractérisé par une première phase de décroissance (ou de stabilité) en fin de printemps, suivie d'une période estivale pendant laquelle la population est stable, avant d'augmenter à nouveau à l'automne, pour atteindre un niveau maximal supérieur à celui de l'entrée de l'été. Enfin, l'hiver, l'abondance chute à nouveau. Ce travail, qui confirme les données générales de la littérature sur les endogés, a cependant montré que par rapport à ce schéma il existait d'importantes variations d'une année sur l'autre, entre A. caliginosa et A. rosea et en fonction des parcelles. Les causes de ces variations, complexes, sont discutées dans cette thèse.Parmi ces causes, le travail du sol, et tout particulièrement le labour, joue un rôle important. Cela nous a amené à mettre en place un essai, sur deux des parcelles du suivi, pour étudier les effets de cette opération sur la dynamique des populations des deux espèces endogées citées ci-dessus. Les résultats obtenus suggèrent que les effets du labour sont variables en fonction de l'espèce considérée. A. caliginosa s'est révélée plus sensible qu'A. rosea, dont les abondances n'ont pas été systématiquement affectées. Celles d'A. caliginosa ont été réduites, juste après le labour en 2009, avec un certain retard (deux mois environ) après cette opération. Ces résultats soulignent ainsi la nécessité d'étudier l'effet des techniques culturales à travers leur impact sur la dynamique des populations (et non sur le niveau d'abondance moyen).La troisième partie de notre travail a été consacrée à l'amélioration du modèle Wormdyn. Nous l'avons tout d'abord adapté au cas de l'espèce A. caliginosa en nous basant sur une étude bibliographique approfondie pour fixer la valeur des paramètres du cycle de vie. Nous avons ensuite introduit une fonction décrivant l'effet de la densité dépendance sur l'abondance. Le modèle a correctement simulé le niveau moyen des abondances mesurées dans les parcelles suivies, malgré une tendance générale à la surestimation des effectifs lorsque les conditions du milieu sont favorables. L'ajout de la densité dépendance a corrigé partiellement ce biais et ouvre à la prise en compte d'autres facteurs de variation des populations, au premier rang desquels la qualité et la quantité des ressources trophiques. / The earthworms fulfil, in the agroecosystems, many services, crucial for the production and proper functioning of the soil. Therefore, it is necessary to deepen our understanding of the drivers of the changes with time of the density and the specific diversity of earthworms communities. Indeed such a knowledge is necessary to predict the effects of the agricultural practices on soil macrofauna and to design cropping systems in organic farming, beneficial to the earthworm abundance. The purpose of this PhD thesis was to analyse, in agricultural fields, the annual variations of the earthworm abundances in the organic farming context of Northern France. We focused on endogeics species, whose abundance was measured during two years (2009 and 2010) in five cropped fields. A model, simulating the earthworm population dynamics of the most abundant species in our cropped fields, A. caliginosa was parametrised with the data collected in thosse fields (and the bibliography). It was also inspired by Pelosi's model (Pelosi et al., 2008). The analysis of the populations dynamics showed a general scheme describing the annual evolution of the abundance (i.e. active endogeic earthworms in the 0-30 cm layer) of these ploughed fields, cropped with cereals. This scheme is characterized by a four-step evolution. a decrease in the abundance (or a stability) at the end of the spring, followed by a summer period with a stability of the population, before an increase at fall, where the abundance reached a higher level compared to the end of spring. Lastly, in winter, the abundance decreases again. This study, which confirmed the general data given by the literature, revealed also significant variations from one year to the other, between A. caliginosa and A. rosea, and also as a function of the crop field. The causes of these variations are discussed in this PhD thesis. Among the possible causes of these variations, soil tillage, especially ploughing, played an important role. This led us to carry out an experiment to study the effects of this practice on the population dynamics of the two endogeic species mentionned above. The results obtained suggested that the effects of the ploughing was species dependent. A. caliginosa was more sensitive than A. rosea, whose abundances were not systematically affected by the ploughing. Those of A. caliginosa were reduced immediately after ploughing in 2009, with some delay (about two months) after this operation. These results emphasize the necessity to study the effect of the agricultural practices through their impact on population dynamics (and not only through the average level of abundance). The third part of our work was devoted to the improvement of the model Wormdyn. We first adapted the model to the species A. caliginosa based on a literature review to determine the the life cycle parameter values for this species. A function describing the effect of density dependence on the abundance was also introduced in the model. The model correctly simulated the average abundances measured in the cropped fields, despite a general tendency to overestimate the abundances, when environmental conditions are favorable. This was only partially corrected by the addition of the density dependence function. The model has to be improved by the introduction of the effect of other factors, first and foremost the quality and quantity of trophic resources.

A Baía de Guanabara é um dos ecossistemas costeiros mais impactados do mundo. Apesar da fauna sublitoral de substratos inconsolidados ser amplamente utilizada como ferramenta ao monitoramento dos impactos de efluentes urbanos, pouco se sabe sobre a biologia das espécies dominantes. Foram analisadas amostras de variáveis ambientais e biológicas da coluna d\'água e do sedimento através de coletas mensais ao longo de um ano em uma estação fixa na Baía de Guanabara (ca. 12 m de profundidade), com objetivo de compreender a estratégia reprodutiva e a dinâmica populacional da espécie Poecilochaetus australis (Annelida: Polychaeta) em local sujeito à influência de efluentes urbanos não-tratados. Os resultados das variáveis ambientais demonstraram pequena flutuação. O sedimento foi composto essencialmente por frações finas de silte e argila com grãos pobremente selecionados, altas concentrações de matéria orgânica total, clorofila-a sedimentar e intensa atividade microbiana na camada superficial. A comunidade foi composta essencialmente por organismos tubícolas e sofreu pouca variação estrutural ao longo do tempo, sendo dominada pelos poliquetas P. australis, Spiochaetopterus nonatoi, Aricidea suecica simplex, Prionospio steenstrupii, pelos anfípodes Tiburonella viscana e uma espécie não identificada da família Corophiidae, uma espécie de isópode da família Anthuridae, o braquiúro Pinnixa sp. e o cladócero Daphnia sp. Não foram verificadas diferenças temporais significativas entre as riquezas e as diversidades específicas. Os valores médios de riqueza e a diversidade específica ficaram entre 15 táxons e 2,77 bits por indivíduo, respectivamente. Houve investimento reprodutivo contínuo das fêmeas de P. australis. A menor fêmea madura (0,8 mm; largura do 7° setígero - D7) foi encontrada em junho de 2005. Grande parte dos indivíduos maduros concentrou-se entre 1,1 e 1,3 mm D7. Os maiores ovócitos foram encontrados no mês de dezembro de 2005 com 163 ?m de diâmetro, e os menores em março de 2006 com 115 ?m. Foram observadas diferenças significativas no grau de desenvolvimento dos ovócitos ao longo do ano com amadurecimento dos ovócitos de um mês para o seguinte. Os ovócitos tenderam a atingir seu ápice de desenvolvimento em dezembro de 2005. Não foi possível determinar sincronismo entre as fêmeas maduras. Não houve variabilidade mensal significativa da abundância de P. australis. O tamanho médio dos 1575 indivíduos amostrados de P. australis ficou em 0,71 mm D7 (dp = 0,36). Foram identificadas oito classes de tamanho. O maior indivíduo foi uma fêmea com 1.5 mm D7 e os menores foram encontrados entre as larvas planctônicas com 0,15 mm D7 e nos recrutas do sedimento com 0,20 mm D7. Em todos os meses, as classes de tamanho inferiores (0,20 - 0,55 mm) estiveram presentes, sendo responsáveis por grande parte da densidade encontrada. O tamanho assintótico de P. australis ficou em 0,97 mm D7, sendo que 79,1% dos indivíduos encontraram-se neste ou abaixo deste tamanho. A constante de crescimento K ficou em 1,7. A taxa de mortalidade ficou em 3,12. Em grande parte do período estudado houve contribuição expressiva de recrutas na abundância de indivíduos, sem que as classes de tamanho maiores fossem excluídas. A população manteve-se estável, já que foi capaz de manter simultaneamente adultos com potencial reprodutivo e alta disponibilidade de larvas e recrutas em ambiente propício ao desenvolvimento, crescimento e reprodução. Não foi encontrado nenhum resultado que apontasse ciclo de vida do tipo oportunista. / Guanabara Bay is one of the most human impacted coastal ecosystems in the world. Despite the wide use of sublittoral soft bottom fauna on urban sewage monitoring programs, little is known about the biology of dominant species. Water column and sediment environmental and biological variables were monthly analyzed in a permanent station in Guanabara Bay (ca. 12 m depth) in order to understand the reproductive ecology and population dynamics of Poecilochaetus australis (Annelida: Polychaeta) in a grossly sewage impacted area. Environmental variables showed only minor fluctuations. Surface sediments were composed of poorly sorted silt and clay fractions, with high concentrations of total organic matter, chlorophyll-a and microbial biomass. The softbottom community structure showed only small, non-significant temporal variations with a large abundance of tube dwellers. Macroinfauna was dominated by the polychaetes P. australis, Spiochaetopterus nonatoi, Aricidea suecica simplex and Prionospio steenstrupii; the amphipods Tiburonella viscana and a non-identified species of the family Corophiidae; a species of the isopod family Anthuridae; the brachiuran Pinnixa sp.; and the cladoceran Daphnia sp. There were no significant temporal differences in species richness and diversity. Mean values for these two parameters were 15 taxa and 2.77 bits ind.-1, respectively. Reproductive output was continuous in P. australis females. The smallest ripe female (0.8 mm; 7th setiger width - D7) was found in June 2005. Most mature individuals measured between 1,1 and 1,3 mm D7. The largest oocytes were found in December 2005 measuring 163 ?m in diameter. The smallest ones were 115 ?m and occurred in March 2006. Significant temporal differences were found in oocyte development with fully matured oocytes occurring every month. However, most oocytes were mature in December 2005. Analysis of ripe females did not show synchronous development. There were no significant differences in numerical abundance of P. australis. Mean D7 size was 0.71 mm (SD=0,36; N=1575). Eight size classes were identified, with the largest individual a female 1.5 mm D7. The smallest individuals were a planktonic larva 0.15 mm D7 and a recently settle recruit 0.20 mm D7. The smallest size classes (0.20 - 0.55 mm D7) were present throughout the sampling period, responding for most of the individuals collected. P. australis asymptotic size was 0.97 mm D7, with over 79% being smaller or at this size. The growth constant K was 1.7 and the mortality rate 3.12. There was a large contribution of newly settled recruits on all studied months. The population was stable, showing the presence of mature adults and a high availability of larvae and recruits. There was no evidence of an opportunist type life cycle for P. australis.

Com o objetivo de obter dados relacionados às estratégias reprodutivas de Hydromedusa maximiliani no Parque Estadual Carlos Botelho, SP, fêmeas e jovens foram radiografados entre setembro de 2007 e dezembro de 2008. A estação reprodutiva estendeu-se de setembro a dezembro, com a ocorrência de desovas entre novembro e dezembro, tanto em 2007 como em 2008. Das 33 fêmeas radiografadas, 19 (58%) apresentaram ovos, e, dessas, apenas três (16%) reproduziram-se nos dois anos. O tamanho da ninhada variou entre 1 e 3 ovos, mas a maioria das fêmeas (90%) apresentou dois ovos. O volume da ninhada foi de 22128,01 ± 4939,8 mm³ (10493,422136,12 mm³; N = 44). Houve fortes relações positivas entre o tamanho corpóreo das fêmeas com o tamanho dos ovos e volume da ninhada. Os dados reprodutivos obtidos no presente estudo, em conjunto com os dados populacionais estabelecidos para H. maximiliani na mesma área de estudo por outros autores, permitiram a realização de uma análise de viabilidade da população. As simulações geradas no programa VORTEX (versão 9.92) foram baseadas em dois cenários principais, denominados População Real (PR) e População Hipotética Isolada (PHI). O primeiro foi criado com base nas informações existentes para H. maximiliani, coletadas ao longo de mais de 10 anos, a partir do qual foram feitas alterações de algumas variáveis (aumento de 10% na taxa de mortalidade; aumento em duas vezes no valor de frequência de catástrofes; inclusão de depressão por endogamia com aumento de 10% no valor default do programa e diminuição da capacidade de suporte), gerando o cenário PHI, com o objetivo de avaliar as diferenças entre uma população protegida em uma unidade de conservação e uma população isolada e sujeita a maiores influências negativas. Os resultados das simulações demonstraram existir diferença significativa (p = 0,0005) entre os dois cenários com probabilidade de extinção equivalente a 31% para o cenário real e 90% para o cenário hipotético. Testes de sensibilidade foram realizados com a finalidade de verificar a influência de variações na taxa de mortalidade, catástrofes e depressão por endogamia, e forneceram indicações de que variações em todos os parâmetros testados possuem forte influência na sobrevivência da população. Estudos de longaduração e informações a respeito das espécies de áreas sujeitas a fortes pressões antrópicas, como a Mata Atlântica, são de grande importância para a conservação, já que podem auxiliar na elaboração de análises de viabilidade populacional e no delineamento de estratégias de manejo focadas nos fatores reais que ameaçam as populações. / The reproductive strategies of Hydromedusa maximiliani at the Carlos Botelho State Park, SP, was verified by X-ray in females and juveniles between September 2007 and December 2008. Throughout the study two reproductive seasons were detected, both beginning in September. From a total of 33 X-rayed females, only 19 showed eggs, and three of them showed eggs in the two reproductive seasons. Clutch size varied from 1 to 3 eggs, but only one female presented one egg and another female presented three eggs. Clutch volume was 22128.01 ± 4939.8 mm³ (10493.422136.12 mm³; N = 44). Female body size was positively correlated to clutch volume, a pattern usually detected in chelonians. Reproductive information acquired in the present study together with population data available for H. maximiliani in the study site makes it possible a population viability analysis using the software VORTEX (version 9.92). A principal scenario (Real Population) was created based on life-history data collected throughout 10 years. In order to compare the protected area with an unprotected hypothetical area regarding the persistence of the population, this scenario was modified by altering some variables (10% increasing of mortality rate, 10% increasing of inbreeding depression, decreasing of carrying capacity), which generates a scenario named Hypothetical Isolated Population. Results were compared and sensitivity tests were carried out to verify the influence of variation in mortality ratio, catastrophes and inbreeding depression. There was a significant difference between the two scenarios (p = 0.0005). The extinction risk was 31% for Real Population and 90% for Hypothetical Isolated Population. The sensitivity analysis indicated that mortality ratio, deforestation, forest fires and inbreeding depression strongly influence the population survival. Long-term studies and biological information on species inhabiting areas subjected to anthropogenic impacts, like the Atlantic Rainforest, are vital to conservation actions, since they make it possible population viability analyses and the design of management strategies to threatened populations.

O Huanglongbing (HLB) é a doença dos citros mais importante em todo mundo, por afetar todas as variedades cítricas cultivadas e ser de difícil controle. No Brasil, onde afeta as principais regiões produtoras de citros, a doença vem se espalhando e causando enormes prejuízos à atividade. O manejo do HLB depende da utilização de ações integradas, dentre elas o controle do inseto vetor, o psilídeo-asiátco-dos-citros, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Para controlar de forma eficiente esse inseto vetor é necessário que se conheça, por meio de amostragens eficazes, suas características de dinâmica tanto temporal quanto espacial, identificando regiões mais propensas à infestações e épocas do ano em que o inseto se desenvolve melhor. Por isso, o presente estudo teve como objetivos: a) avaliar a dinâmica temporal do psilídeo D. citri em pomares do Estado de São Paulo, examinando o efeito de diferentes regiões, épocas do ano e idade dos plantios; b) verificar a existência de diferenças no número de insetos amostrados em diferentes alturas da planta cítrica, comparando diferentes métodos de amostragem; e c) investigar o padrão de distribuição espacial do inseto em pomares de diferentes idades. Para isso foram realizados levantamentos ao longo de dois anos em seis localidades, representativas de três regiões do parque citrícola paulista, com pomares de diferentes idades, sendo amostradas todas as fases de vida de D. citri e brotações cítricas. Para a avaliação da amostragem de psilídeos em diferentes alturas, foram estudados dois pomares com plantas de diferentes idades, com avaliação da densidade de psilídeos e brotos cítricos em vários estratos da planta, comparando-se dois tipos de amostragem de insetos adultos. Para o estudo da distribuição espacial de D. citri foram feitos levantamentos em pomares de dois municípios da região citrícola central, analisando-se os dados com geoestatística. Foram constatados efeitos de região, idade dos plantios e épocas do ano sobre a população de D. citri. As maiores populações do inseto estão presentes na região central, onde o inseto ocorre com maior frequência ao longo do ano, seguida da região noroeste e sul. Mais ninfas ocorreram em pomares mais jovens, mas a população de adultos não necessariamente ocorre em maiores números nestes locais. A primavera foi a estação do ano na qual ocorreram as maiores populações de insetos, mas elevações populacionais podem ocorrer em qualquer época desde que haja brotações presentes e que o clima seja favorável. A altura de amostragem influenciou o número de adultos de D. citri detectados no pomar mais velho e de todas as fases de vida do inseto no pomar mais novo, bem como o número de brotações cítricas. Amostras mais precisas foram geradas pela amostragem com armadilhas adesivas do que visualmente, sendo recomendada a amostragem de D. citri com armadilhas em pontos mais elevados da planta para melhor precisão. D. citri apresentou distribuição agregada e forte dependência espacial na maioria das datas de amostragem e em pomares de diferentes idades. Focos foram identificados nos pomares, com área de 1.257 m², em média. / Huanglongbing (HLB) is the most important citrus disease in the world, affecting all cultivated citrus varieties, and it is very difficult to control. In Brazil, HLB is spreading in the major citrus producing areas and causing huge losses to the citriculture. Disease management depends on integration of different methods, including control of the insect vector, the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). In order to effectively monitor and control this vector, it is necessary to understand his population dynamics in citrus orchards, identifying regions and seasons where the insect develops higher populations. This study was designed to investigate the temporal and spatial dynamics of D. citri in citrus orchards of Sao Paulo State, examining the effect of different regions, seasons and plant age. Surveys of psyllid populations and citrus shoots were carried out over two years in six locations, representing three growing regions of São Paulo State, in citrus orchards of different ages, where all life stages of D. citri and citrus shoots were sampled. The spatial distribution of D. citri was analyzed by geostatistics in orchards of two municipalities of the central region of São Paulo State. The efficacy of sampling methods (yellow sticky cards vs. visual inspections) and sampling height on the tree canopy for estimating psyllid populations and number of citrus shoots was investigated as well; this particular study was conducted in two orchards of different ages, in the central region. Significant effects of region, orchard age and seasons of the year on the population of D. citri were observed. The highest insect populations are present in the central region, where the insect occurs more frequently throughout the year, followed by the northwestern and southern regions of São Paulo State. More nymphs occurred in younger orchards, but the adult population does not necessarily occur in higher numbers in the younger orchards. Spring was the season of highest populations of D. citri, but population increases can occur at any time if there are shoots present and the weather is favorable. The sampling height influenced the number of D. citri adults trapped by yellow sticky cards in the older orchard, and the numbers of psyllid eggs, nymphs and adults, as well as of citrus shoots, visualized on the younger orchard. More accurate sampling data were generated by using yellow sticky traps compared with visual inspections. Yellow sticky traps should be placed closer to the top of the citrus tree for better accuracy. D. citri showed aggregated pattern and strong spatial dependence in most sampling dates and in orchards of different ages. Foci were identified in the orchards, with a mean area of aggregation of 1,257 m².

Procurou-se avaliar o impacto das ações de esterilização animal na dinâmica populacional canina no município de São Paulo, bem como sugerir um método de controle a fim de se manter todos os distritos administrativos com uma população homogeneamente castrada. Os resultados foram comparados com as ações realizadas atualmente pelo órgão municipal de controle animal. Foram avaliadas taxas de esterilização de 10, 20, 30, 40, 50 e 60% ano-1 para a população canina total ao longo de 5, 10, 15 e 20 anos aplicando-se modelo matemático de dinâmica populacional para dois sexos, sem diferenciação etária. Demonstrou-se que com uma taxa de 60% ano-1 ocorre diminuição de 56,05% da população canina após 20 anos de programa permanente de esterilização animal. Para se obter 20% da população canina homogeneamente castrada por distrito administrativo no município após 10 anos foi avaliada a necessidade de se utilizar uma taxa mínima de esterilização de 5% ano-1. Verificou-se que a taxa de esterilização de 2,7% realizada em 2011 e 2012 pelo município é baixa para se diminuir a população canina total e que há necessidade de se melhor alocar os locais onde se realizam cirurgias no município, sendo o local de maior urgência a região sul do município, A distribuição homogênea de clínicas conveniadas à prefeitura em cada um dos distritos administrativos apresentaria melhores resultados em relação aos mutirões. / This work aimed to evaluate the impact in the canine population dynamics through the neutering activities done by São Paulo city, as well as suggest a control method in order to maintain a homogenous neutered population in each administrative districts. The results were compared with the activities currently done by the animal control organization. 10, 20, 30, 40, 50 and 60% annual neutering rates were evaluated applying a mathematical model for two sexes, without age differentiation. It was demonstrated that applying a 60% annual rate produces 56,05% diminishment in the canine population after 20 years of neutering permanent activities. In order to obtain 20% of the canine population homogeneously neutered per administrative district a minimum 5% neuter rate would be necessary. It was verified that the 2,7% neuter rate applied by the municipality in 2011 and 2012 was low in order to diminish the canine population and that it is necessary to relocate the places where most the surgeries are done, more urgently the south region of São Paulo. The homogenous distribution of hired clinics by the municipality in each administrative district would present better results than the neutering campaigns currently done by the animal control organization.

Entre os grandes desafios da ecologia está a previsão e o entendimento das flutuações que ocorrem nas populações biológicas. Quando agregamos as intervenções humanas a esse entendimento, podemos, ao mesmo tempo em que fazemos previsões acerca do futuro das populações, entender melhor seus processos naturais de regulação e controle. Neste trabalho, realizamos um estudo da ecologia de duas espécies arbóreas tolerantes à sombra (Guapira opposita (Vell.) Reitz, pertencente ao dossel e Rudgea jasminoides (Cham.) Müll.Arg., pertencente ao sub-bosque) a fim de responder à questão de como a estrutura, a dinâmica populacional e o desempenho de plântulas respondem à heterogeneidade ambiental causada por distúrbios relacionados à fragmentação e à sucessão secundária. No Capítulo 1, testamos se a estrutura populacional, medida pela distribuição de tamanhos, está relacionada ao tamanho e/ou ao estádio sucessional do fragmento. A partir das conclusões geradas nesse primeiro estudo, no Capítulo 2 verificamos se parâmetros da dinâmica populacional, como a taxa assintótica de crescimento e as taxas vitais, explicam as variações encontradas na densidade e na estrutura. No Capítulo 3, testamos se o desempenho das plântulas destas espécies é afetado pelos fatores abertura do dossel e profundidade da serapilheira, os quais são reconhecidamente promotores da heterogeneidade ambiental em fragmentos florestais secundários. Para tanto, marcamos e acompanhamos por dois anos (de 2007 a 2009) populações das duas espécies em seis fragmentos de floresta secundária de distintos estádios sucessionais no Planalto Atlântico Paulista. Quanto à estrutura populacional, Guapira mostrou uma variação associada ao grau de estruturação da floresta, enquanto que para Rudgea o tamanho do fragmento foi a variável explicativa mais importante, o que nos levou a hipotetizar que Rudgea corre risco de extinção local nos fragmentos médios. Com relação às análises de dinâmica populacional, Rudgea apresentou um tempo de duplicação da população 4,5 vezes maior nos fragmentos médios do que nos grandes, o que nos leva a concluir que o risco de extinção local pode ser atenuado ou mesmo revertido. Para Guapira, as taxas não diferiram entre os estádios sucessionais, sendo previstas populações estáveis para ambos (955;8776;1). As análises do efeito da abertura do dossel e da profundidade da serapilheira no desempenho das plântulas demonstraram a importância da interação entre os fatores e a relevância de se considerar as diferentes fases ontogenéticas das plântulas. Através de uma abordagem inédita, demonstramos a importância do emprego de enfoques complementares (estrutura e dinâmica) para que se possa de fato entender o que ocorre em nível populacional. Além disso, destacamos a importância dos estudos de dinâmica para se elucidar os mecanismos demográficos atuantes em cada população. Esse conhecimento é uma ferramenta fundamental para o planejamento de ações direcionais de manejo e conservação. / One of the greatest challenges of ecology is to understand and predict the fluctuations in the biological populations. When we consider the human intervention in this understanding, we can, at the same time, make predictions about the future of the populations and understand better their natural processes of regulation and control. In this work we carried out a study about the ecology of populations of two shade tolerant tree species (Guapira opposita (Vell.) Reitz, that occupies the canopy and Rudgea jasminoides (Cham.) Müll.Arg., that occupies the understory) to answer the question of how the structure, population dynamics and seedling performance respond to environmental heterogeneity caused by disturbances related with fragmentation and secondary succession. In the first chapter we tested if the population structure, measured by size distributions, is related to the size and/or to the successional stage of the fragment. From the conclusions generated in this first study, in the second chapter we evaluated if population dynamics parameters, such as asymptotic growth rate and vital rates explain the variation in density and structure. In the third chapter we tested if the seedling performance of these species is affected by canopy openness and litter depth, which are known promoters of environmental heterogeneity in secondary forest fragments. In order to achieve this goal we marked and followed by two years (2007- 2009) populations of both species in six secondary forest fragments of different successional stages in the Southeast Atlantic Plateau. Regarding the population structure, Guapira showed variation associated to the degree of forest structuring, while for Rudgea the fragment size was the most important explanatory variable, what lead us to hypothesize that Rudgea is in risk of local extinction in the medium fragments. Regarding the analysis of population dynamics, Rudgea showed a population doubling time in the medium fragments 4.5 times greater than in the large ones, what lead us to conclude that this risk of local extinction can be mitigated or even reversed. For Guapira, the rates did not differ between the successional stages, being predicted stable populations in both (955;8776;1). The analysis of the effect of the canopy openness and the litter depth in the seedling performance showed the importance of the interaction between these factors and the relevance of considering the different seedling ontogenetic stages. Through a new approach, we demonstrated how important is to consider complementary studies (structure and dynamics) in order to really understand what happens at population level. Besides, we highlight the importance of studies with dynamics in order to elucidate the demographic mechanisms that occur in each population. This knowledge is a fundamental tool for planning more directional management and conservation actions.