Conservation of natural habitats and planting wildflower plots are two commonly promoted tactics to enhance pollination services and biological control of crop pests, which are ecosystem services that can improve agricultural outputs. There are several programs at various levels of government in the United States that landowners can use to defray the costs of implementing these conservation strategies. Studies of European Agricultural Environmental Schemes have shown these tactics to have positive outcomes for crop production. However, real-world applications of cost-sharing programs have not been evaluated in the United States on pollination services and biological control. Furthermore, these tactics may inadvertently perform ecosystem disservices, like increasing crop pests or creating habitat for disease vectors. In this study, we evaluated the effects of natural habit and wildflower plots on biological control, pollination services, bee communities, and tick populations in Eastern Virginia and Maryland. This research was conducted on 22 farms. 10 of these farms had wildflower plots that were designed by Natural Resource Conservation Service personnel, and implemented by cooperating farmers. Collards, strawberries, tomatoes, and squash were used as model systems. We measured pest density, sentinel egg predation, crop damage, seed pollination, biomass production, marketable crop yield, sampled the bee community, and recorded tick abundance in wildflower plots. Many of the measures of biological control and pollination services had idiosyncratic results in regards to the wildflower plots and natural habit in the landscape. However, the proportion of high quality yield for all four crops increased with increasing natural habitat in the landscape. Bee communities between sites with and without wildflower plots were not different. Bee abundance did increase at wildflower sites when natural habitat comprised a certain proportion of the habitat around the site. Ticks were sampled from wildflower plantings, but not in greater abundance compared to field margins. In this study, the effects of wildflower plots were overshadowed by the landscape effects of natural habitat. Government personnel that oversee these programs may need to consider the surrounding landscape when helping implement on-farm conservation measure like wildflower plots. Such measures, do not perform an ecosystem disservice in regards to ticks. / Doctor of Philosophy / Conservation of natural habitats and planting wildflower plots are two strategies to enhance pollination services and biological control of crop pests. These two ecosystem services are of needed to improve agricultural production without further damaging the environment. There are several programs at various levels of government in the United States that landowners can use to subsidize the costs of implementing these strategies. European studies have shown these government programs to be successful. However, these programs have not been evaluated in the United States on their ability to enhance pollination services and biological control. Furthermore, studies investigating potential ecosystem disservices these strategies. In this study, we evaluated the effects of natural habit and wildflower plots on biological control, pollination services, bee communities, and tick populations in Eastern Virginia and Maryland. This research was conducted on 22 farms. 10 of these farms had wildflower plots that were designed by Natural Resource Conservation Service personnel, and implemented by cooperating farmers. Collards, strawberries, tomatoes, and squash were used as model systems. We measured pest density, egg predation, crop damage, seed pollination, and yield. We also sampled the bee community, and recorded tick abundance in wildflower plots. There were no consistent trends for many measures of biological control and pollination services in response to the wildflower plots and natural habit. However, the proportion of high quality yield for all four crops increased with increasing natural habitat in the landscape. Bee communities between sites with and without wildflower plots were not different. Bee abundance did increase at wildflower sites when natural habitat comprised a certain proportion of the habitat around the site. Ticks were sampled from wildflower plantings, but not in greater abundance compared to field margins. In this study, the effects of wildflower plots were overshadowed by the landscape effects of natural habitat. Government personnel that oversee these programs may need to consider the surrounding landscape when helping implement on-farm conservation measure like wildflower plots. Such measures, do not perform an ecosystem disservice in regards to ticks.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Our planet is in the midst of a biodiversity crisis, with factors such as land transformation, climate change, anthropomorphic disturbance and invasive species acting together to threaten biodiversity. In South Africa, with minimal natural wood resources, commercial forestry is one of the most abundant forms of landscape transformation. However, a third of the land inside many plantations has been set aside for conservation as unplanted remnant grassland patches (RGPs). These areas are subjected to an additional negative impact by invasive alien species, namely Rubus cuneifolius (American bramble), a weed that is particularly problematic in and around forestry plantations in South Africa. The grassland biome of South Africa is extremely diverse and is of vital importance for the ecosystem services it supplies. Despite this, the grassland biome is under threat as this is where much of South Africa’s forestry plantations are located. Driven by anthropomorphic disturbance, pollinators are in decline. Landscape transformation of natural areas for forestry plantations is likely to affect plant-pollinator interactions which will affect ecosystems and biodiversity. However, it is not known to what extent these ecosystems are affected. It is thought that the impact depends on the complexity of the ecosystem in question, and analyses at the network-level provide insights into the robustness of ecosystems in the face of biodiversity loss. Thus, this study evaluates the effect of natural habitat fragmentation and invasion of the alien species, R. cuneifolius, on flower visitation networks of South African grasslands. The study was conducted in the KwaZulu-Natal Midlands within a commercial timber plantation and a neighbouring protected area (PA). Flower-visitor observations were carried out in uninvaded protected areas and RGPs and in protected areas and RGPs invaded by R. cuneifolius. I found that RGPs within commercial forestry plantations successfully decrease the negative effects of land transformation on the grasslands of the KwaZulu-Natal Midlands, and flower visitation network patterns are largely maintained in these habitat fragments. However, within RGPs, invasion by R. cuneifolius affected the composition and the interaction network structure of flower-visitor and plant communities. The fact that there are unplanted areas within commercial forestry plantations is positive for biodiversity conservation in South Africa. Research has indicated that these areas successfully aid in the conservation of biodiversity and ecosystem functioning. Due to the positive influence that RGPs have on conservation in fragmented and transformed landscapes, it is critical that these unplanted areas are retained. However, the effects of bramble invasion are more intense within RGPs than within protected areas, and therefore, it must be a priority to keep these areas undisturbed. R. cuneifolius has been found to have devastating effects on ecosystem function and network structure. It is also a category 1 invasive plant within South Africa, and its removal is required by law. Therefore, the removal of bramble must be a management priority. / AFRIKAANSE OPSOMMING: Ons planeet is in die middel van 'n biodiversiteit krisis, met faktore soos grond transformasie, klimaatsverandering, antropomorfiese versteuring en indringerspesies wat gesamentlik werk om biodiversiteit te bedreig. Suid-Afrika, besit minimale houtbronne. Daarom is kommersiële bosbou een van die mees algemene vorme van landskap transformasie. Tog is 'n derde van die land binne baie plantasies opsy gesit vir bewaring as oorblywende grasveld kolle (OGKs). Hierdie gebiede word ongelukkig blootgestel aan die bykomende negatiewe impak van die uitheemse spesies, Rubus cuneifolius (Amerikaanse steekdoring), wat veral problematies is in en rondom bosbouplantasies. Die grasveldbioom van Suid-Afrika is baie divers en is van kardinale belang vir die ekosisteem dienste wat dit lewer. Ten spyte hiervan, word die grasveldbioom bedreig waar dit op dieselfde areas as die meerderheid van Suid-Afrika se bosbouplantasies geleë is. Antropomorfiese versteuring lui daartoe dat bestuiwergetalle daal. Landskap transformasie vir bosbou plantasies raak dus plant-bestuiwer interaksies, wat ekosisteme en biodiversiteit beïnvloed. Dit is nie bekend tot watter mate hierdie ekosisteme geraak word nie. Daar word vermoed dat die impak af hang van die kompleksiteit van die ekosisteem. Ontledings van ekosisteme op netwerk vlak kan insigte bied oor die robuustheid van hierdie ekosisteme in die aangesig van biodiversiteitverlies. Dus, die studie evalueer die effek van fragmentasie van natuurlike habitatte en inval van die indringer spesie, R. cuneifolius, op blom-besoekings netwerke van Suid-Afrikaanse grasvelde. Hierdie studie is uitgevoer in die KwaZulu-Natal Midlands binne 'n kommersiële hout plantasie en 'n naburige beskermde gebied (BG). Blom-besoeker waarnemings was in BGs en OGKs sonder R. cuneifolius, en in BGs en OGKs met R. cuneifolius uitgevoer. Ek het gevind dat OGKs binne kommersiële bosbouplantasies suksesvol is om die negatiewe uitwerking van land transformasie te verminder, en blom-besoeking netwerk patrone grootliks gehandhaaf word in hierdie habitat fragmente. Egter, binne OGKs, het R. cuneifolius die samestelling en die interaksie netwerk struktuur van blom-besoekers en plant gemeenskappe negatief geraak. Die feit dat OGKs ongeplant gelaat word, is positief vir die bewaring van biodiversiteit in Suid- Afrika. Navorsing dui aan dat hierdie gebiede suksesvol is om te help met die bewaring van biodiversiteit en ekosisteemfunksionering. As gevolg van die positiewe invloed van OGKs op bewaring in gefragmenteerde en omskepte landskappe, is dit krities dat hierdie areas ongeplant bly. Egter, die gevolge van steekdoring inval is meer intens binne OGKs as binne beskermde gebiede, en daarom moet dit 'n prioriteit wees om hierdie gebiede ongestoord te hou. R. cuneifolius se verwoestende uitwerking op ekosisteem funksie en netwerk struktuur was baie duidelik. Dit is ook 'n kategorie 1 indringerplant in Suid-Afrika, en sy verwydering word deur is die wet vereis. Daarom moet die verwydering van steekdoring ‘n bestuursprioriteit wees.

<p>This&nbsp / thesis&nbsp / examines&nbsp / the&nbsp / changes&nbsp / that&nbsp / have&nbsp / occurred&nbsp / within&nbsp / West-Coast Renosterveld within&nbsp / the&nbsp / last 350 years, and assesses&nbsp / the viability of&nbsp / the&nbsp / remaining fragments.</p>

<p>This&nbsp / thesis&nbsp / examines&nbsp / the&nbsp / changes&nbsp / that&nbsp / have&nbsp / occurred&nbsp / within&nbsp / West-Coast Renosterveld within&nbsp / the&nbsp / last 350 years, and assesses&nbsp / the viability of&nbsp / the&nbsp / remaining fragments.</p>

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The Antillean manatee, Trichechus manatus manatus, is the most endangered aquatic mammal in Brazil. Its current distribution in the country is restricted to the northern and northeastern coast, between the states of Amapá and Alagoas, with some discontinuities. A reintroduced manatee, known as Astro, has been living in Sergipe for more than ten years. It is one of the first animals released back into the wild by the reintroduction program created by the Manatee Project. The principal objectives of the present study were to evaluate the behavior of Astro, in particular his habitat use, the effects of the construction of the bridge over the Vaza-Barris River, which crosses his main range, and his relationship with the local communities, with a view to the development of management strategies adequate for the establishment of a local population of T.m. manatus. The research was based on the monitoring of Astro between November, 2006, and November, 2009, over a total of xx days, involving xx hours of direct observation. The animal s movements were based using a GPS, and a survey of the available dietary resources was carried out in the Vaza-Barris Estuary. To evaluate the relationship with the local community, 27 local residents were interviewed. The behavioral monitoring indicated normal patterns for the species, although the animal s habit of approaching boats was identified as a potentially serious problem, especially when it interfered with residents fishing activities. Despite the overall tolerance of most residents, a few cases of mistreatment were reported, indicated a clear need for guidance and tutoring in order to guarantee the peaceful coexistence of the animal and local communities. In contrast with expectations, the construction of the bridge did not appear to have had a significant negative effect on the animal s behavior, possibly because the main disturbance did not coincide with the principal area occupied by the animal. The two main conclusions of this research are that the study area appears to provide an adequate site for the establishment of a resident population of T.m. manatus, which would be a significant advance for the conservation of the subspecies, but also that this would require the careful deployment of an environmental awareness program in the local communities of river-dwellers. / O peixe-boi marinho, Trichechus manatus manatus, é o mamífero aquático mais ameaçado de extinção no Brasil. Atualmente, sua distribuição no país é restrita ao litoral norte - nordestino com algumas áreas de descontinuidade entre os estados do Amapá e Alagoas. Em Sergipe, reside há mais de dez anos um peixe-boi reintroduzido conhecido como Astro, um dos primeiros representantes desta espécie a ser solto pelo programa de reintrodução criado pelo Projeto Peixe-boi. Os principais objetivos da presente pesquisa foram avaliar o padrão comportamental do Astro, seu uso de habitat, os efeitos da construção da ponte sobre o rio Vaza-Barris, que atravessa sua principal área de permanência, e sua relação com as comunidades locais, visando o desenvolvimento de estratégias de manejo adequadas para o estabelecimento de uma população local de T. m. manatus. A pesquisa foi baseada no monitoramento do Astro entre novembro/2006 e novembro/2009, com um total de 1095 dias de monitoramento e 426 horas de observação direta. Seus movimentos foram mapeados usando um GPS e foi realizado um levantamento dos recursos alimentares disponíveis no estuário do Vaza-Barris. Para avaliar sua relação com a comunidade local, 27 moradores foram entrevistados. O monitoramento comportamental indica um padrão normal para a espécie, embora seu hábito de se aproximar de embarcações constitui um problema potencialmente sério, especialmente quando interfere nas atividades de pesca dos moradores. Apesar de certa tolerância por parte da maioria dos moradores, alguns casos de maus-tratos foram relatados, e ficou clara a necessidade de orientação e conscientização para garantir o convívio pacífico entre o animal e as comunidades locais. Ao contrário do esperado, a construção da ponte não parecia ter tido um efeito significativamente negativo sobre o comportamento do animal, possivelmente porque o maior impacto não coincidiu com a área mais frequentada por ele. As duas conclusões principais são que a área de estudo parece constituir um sítio adequado para o estabelecimento de uma população residente de T.m. manatus, que seria um avanço significativo para a conservação da subespécie, mas que isto também necessitaria do desenvolvimento cuidadoso de um programa de conscientização ambiental junto às comunidades locais.

Philosophiae Doctor - PhD / South Africa

Développer des systèmes de culture respectant voire favorisant la biodiversité est un enjeu important pour les agronomes dans le contexte sociétal actuel. Pour ce faire, ceux-ci ont besoin de méthodes prédictives d’évaluation des effets des pratiques agricoles sur la biodiversité pour caractériser et évaluer les systèmes étudiés. Les écologues reconnaissent la nécessité d’aborder la biodiversité non seulement comme la richesse spécifique mais aussi par le biais des services écosystémiques qu’elle peut rendre à l’homme. Il existe de nombreuses propositions d’indicateurs de biodiversité mais ceux-ci reposent, soit sur des mesures de diversité au sein de groupes taxonomiques, soit sur des variables de pratiques et ne sont pas prédictifs. L’objectif de la thèse a été de concevoir un indicateur prédictif des effets des pratiques agricoles sur la biodiversité et ses services. Pour effectuer ce travail, nous avons choisi de nous baser sur la diversité floristique en bordure de champ et sur les services qui lui sont liés : la valeur patrimoniale, enjeu sociétal et la pollinisation, enjeu majeur pour l’agriculture. Nous avons structuré ce travail en trois étapes. En premier lieu, nous avons sélectionné les pratiques agricoles connues pour leurs effets combinés sur la biodiversité et ses services, identifié leurs natures et estimé l’ampleur de leurs effets à l'échelle de la bordure de champ. Dans une seconde étape, nous avons intégré par expertise la connaissance sur ces effets dans un modèle opérationnel.A la suite de ce travail de conception, nous avons évalué la sensibilité, et la qualité prédictive du modèle en le confrontant à un jeu de données mesurées sur le terrain dans le cadre de la thèse ou acquises dans le cadre d’autres travaux. Enfin, nous avons transformé les sorties du modèle (probabilité de présence pour 338 espèces) en un indicateur en les agrégeant en une valeur synthétique. Nous avons positionné ensuite celle-ci par rapport à des références que nous avons sélectionnées, et sur une échelle de notation lisible. Le développement de cet indicateur prédictif opérationnel permettra aux agronomes d’évaluer les effets positifs et négatifs des pratiques agricoles, et d’identifier des pratiques innovantes respectueuses de la biodiversité et de ses services. L’indicateur pourra être utilisé avec d’autres indicateurs environnementaux, économiques et sociaux dans la perspective de l’étude de la durabilité des exploitations agricoles en grandes cultures. / Developing cropping systems supporting biodiversity is an important goal for agronomists in the current context of society. To achieve this goal, they need predictive methods assessing the effect of cropping practices on biodiversity to characterize and evaluate cropping systems. Among ecologists, a growing agreement exists to address biodiversity not only as species richness but also as ecosystemic services. There are numerous proposals of biodiversity indicators but those are based on diversity measurement within taxonomic groups or on management variables, and are not predictive. The objective of the thesis is to design a predictive indicator to assess the effects of cropping practices on biodiversity and its services. To achieve this, we decided to address plant diversity and its associated services, conservation value, a stake for society, and pollination, important stake for agriculture. We structured the thesis in three steps. First we selected cropping practices having combined effects on biodiversity and its services, identified their nature and assess the range of their effects at the field margin scale. In a second step, we integrated by expertise, this knowledge in an operational model. Following the design, we evaluate the sensitivity and the predictive quality of the model by comparing model outputs with field measurements carried out during the thesis or outside. Last we transformed outputs of the model (in form of presence probability for 338 species) into an indicator by aggregating them into synthetic value. Then, this was calibrated to selected references values on a scale between 0 (unfavorable) and 10 (favorable) easy to understand. The development of this operational predictive indicator will enable agronomists to assess positive and negative effects of cropping practices and to identify innovative practices supporting biodiversity and its services. The indicator can be used with other environmental, economic, and social indicators to assess sustainability of arable farming systems

Made available in DSpace on 2015-04-20T12:31:14Z (GMT). No. of bitstreams: 1 francisco.pdf: 1029822 bytes, checksum: a55ebb42d97e615744cc7460ffefa1d1 (MD5) Previous issue date: 2011-03-24 / Caferana Picrolemma sprucei Hook a plant from the Simarubaceae family with antimalarial effects well known by the Amazon region native populations is being used without any criteria by them as a medicinal tea in order to fight this disease. The plant has a taproot that could reach over 2mts depth. On chapter one, it has been researched the regrowing of the species in its own habitat, in order to evaluate the increment of vegetal material, in a given period of four years to attain technical information on cultivated stuff and a sprout production method. The selected part of plant was the stem in natural habitat, close-cut regrowing at ground-surface. The population had 75% of plants with average height of 50 cm. On following four years, after being cut to measure average height, 75 % of plants have reached maximum height between 28 to 30cm. As a main conclusion, it could be inferred that, according field observation the caferana plant needs at least the minimum of four years to recompose its growth after being cut. It has been observed a rather slow regrowth increment, because unknown factors. On chapter two, it has been used the agronomic stake technique aiming at to evaluate plant viability for sprout production. It was adopted a casual design experiment absolutely at random in factorial scheme 4 x 4 with four types of stakes ligneous, semi-ligneous, herbaceous and semi-herbaceous and four types of soil; S1 with sand 100%, S2 with 50% sand plus 50% clay, S3 with clay 100%, and S4 with composite soil 30% plus 30% clay plus 40% sand. Best kind of soil for caferana has been S4 composite 21,67%, and best stakes were: ligneous 29,16% and herbaceous 20%. On a general mood, roots were only established after one and a half year of sprout maintenance, turning rather difficult its identification, diminishing sprout development, making non-feasible the stake-technique for sprout production. On chapter three, it has been evaluated caferana plants sprouting with seeds collected at UFAM-AM. The experiment was sketched in blocks at random, with four types of soils; S1 (100% sand); S2 (50% sand plus 50% clay); S3 (100% clay) S4 (30% composite plus 30% clay plus 40% sand), during four years. At the green-house caferana has been watered with automatic sprinkling every ten minutes at 60 second - irrigating period. The largest percentage sprouting average was with substratum S4 (41.02%) followed by S3 (31.92%) and S2 (30,29%) which do not differed between them. The worst performance has been for substratum S1 (22,94%). Germination techniques in green-house, for Picrolemma spruce Hook sprout production has had a rather medium yield. It has been concluded that there is a great dependence on moisture for this species germination, already proved by best treatments (S4, S3, S2), containing (clay and humus) moisture retaining particles, which was also verified in its habitat next to Igarapes (creeks), where they develop in larger quantities. It is highly recommended to test other sprout production techniques, as in B.O.D chambers where could prove better results than in soil substrata germination. On chapter four, it has been evaluated the analysis by genetic markers conducted by three different combinations of four EcoRI-Msel starters, resulting in a total number of 443 polymorphic bands. These data has been used for the analysis of genetic divergence among populations. It was observed low-levels of genetic divergence among them. Genetic similarity at must has been of 88.8% inside C population, 39% inside D population, being similar inside P population, indicating, and lower genetic variability on C population, then influenced to endogamy crossing. Clustering populations has being displayed in the form of a dendrogram; inferring that, populations with greater Jaccard coefficient tend to have more similarity, and trees next to each other tend to be more similar among them. / Atualmente, há um grande interesse em plantas para extração de princípios ativos com atividade antimalárica, principalmente na Amazônia, onde a doença já se alastra há tempos, sem uma ação eficaz para sua erradicação. A Caferana (Picrolemma sprucei Hook. f.) é uma planta Simaroubaceae, conhecida como antimalárica por povos nativos da região Amazônica, sendo utilizada sem critérios como chá medicinal para combate à doença. A planta possui uma raiz pivotante e atinge em torno de 2 m de profundidade. No capítulo I, foi investigado o recrescimento da espécie em seu habitat, a fim de avaliar o incremento do material vegetal, num período de quatro anos, para obter informações sobre recrescimento do material selvagem e o melhor método de produção de mudas. A planta foi cortada no caule (corte rente à superfície do solo) em seu habitat natural. A população original apresentava 75% das plantas com altura média de 50 cm. Nos quatro anos seguintes, o recrescimento médio de 75% das plantas atingiu a altura de (28 a 30 cm). Concluiu-se que a planta necessita, conforme observações em campo, não menos que quatro anos para se recompor em recrescimento depois de cortada. Tendo um incremento de recrescimento lento e com grande variabilidade, devido a fatores desconhecidos. No capítulo II, utilizou-se a técnica agronômica de estaquia a fim de avaliar a viabilidade na propagação da planta nativa para produção de mudas. Adotou-se experimento em delineamento inteiramente ao acaso em esquema fatorial (4X4) com quatro tipos de estacas (lenhosa, semi-lenhosa, herbácea e semi-herbácea) e quatro tipos de substratos: (S1) com areia (100%); (S2) com 50% de areia + 50% de solo argiloso; (S3), com solo argiloso (100%); e (S4) com 30% de terra compostada + 30% de solo argiloso + 40% de areia). O melhor substrato para caferana foi o compostado S4 (21,67%), e as melhores estacas foram: lenhosa (29,16%) e herbácea (20%). De um modo geral, as raízes só apareceram após um ano e meio de manutenção da muda, tornando difícil sua identificação, diminuindo o desenvolvimento da muda e inviabilizando a técnica de estaquia para produção das mudas nativas. No capítulo III, avaliou-se a germinação de plantas de caferana com sementes coletadas na UFAM/AM. O experimento foi delineado em blocos ao acaso, com quatro tipos de substratos: S1 (100% areia); S2 (50% areia + 50% solo argiloso); S3 (100% solo argiloso) e S4 (30% composto + 30% solo argiloso + 40% areia). Na casa de vegetação regou-se com aspersão automática a cada 10 min., com período de rega de 60s. A maior percentagem média de germinação foi com o substrato S4 (41,02%) seguido de S3 (31,92%) e S2 (30,29%) que não diferiram entre si. Obtendo o pior desempenho o substrato S1 (22,94%). A técnica de germinação em casa de vegetação para produção de mudas da espécie Picrolemma sprucei, apresentou um rendimento apenas mediano. Conclui-se que há dependência de umidade para germinação da espécie, provada pela composição dos melhores tratamentos S4, S3 e S2, contendo partículas redutoras de argila e húmus, grande retentora de água, e, também verificada em seu habitat, próximas aos igarapés, se desenvolvem em maior quantidade. Recomenda-se testar outras técnicas de produção de mudas, em câmaras de BOD, onde poderá demonstrar melhores resultados do que a germinação em substratos de solo. Com relação ao experimento com marcador molecular AFLP, capítulo IV, obteve-se um índice de similaridade genética máxima em torno de 29% para a população P (ZF2), 33% para apopulação D (Ducke) e o maior índice em torno de 87% para a população C (cultivada), mostrando definitivamente a baixa variabilidade genética em populações cultivadas, possivelmente devido ao endocruzamento. A análise por marcador genético foi realizada por sete diferentes combinações de iniciadores EcoRI-MseI, resultando num total de 443 bandas polimórficas. Esses dados foram utilizados para análise da divergência genética entre populações e dentro delas. Foram detectados baixos níveis de divergência genética entre populações. O máximo de similaridade genética foi de 88,8%, dentro de população C , o de 39% dentro da população D e semelhante dentro da P (39%), indicando uma menor variabilidade genética na população C que ficou sujeita a cruzamentos endogâmicos. O agrupamento das populações, a partir do dendrograma (Apêndice I) encontrado, sugere que populações com maior coeficiente de JACCARD, tenham maior similaridade e árvores próximas tendem a ser mais similar entre si.

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Les abeilles sont des pollinisateurs essentiels pour les cultures et les plantes sauvages, mais l'intensification des pratiques agricoles a engendré une baisse importante de leur abondance et diversité. Afin de protéger efficacement les abeilles dans les paysages agricoles, il est nécessaire d'avoir une meilleure connaissance de leurs patrons de diversité. L'objectif général de cette thèse était de déterminer les patrons spatio-temporels de la diversité des abeilles et l'utilisation des ressource fleuries dans un système agricole intensif. L'échantillonnage spatialement extensif de l'activité de butinage des abeilles sauvages et domestiques nous a permis de recenser 45040 individus (29314 abeilles domestiques et 15726 sauvages), appartenant à 192 espèces recensées à l'échelle territoriale. Cette diversité représente près de 20% de la richesse des espèces apiformes connues à l'échelle nationale. Cette communauté est caractérisée par une forte proportion d'espèces rares (28,8%) et de fortes variations temporelles et spatiales, en particulier de l'échelle locale jusqu'à 10-20 km2. L'importance des habitats semi-naturels pour soutenir les populations d'abeilles sauvages a été confirmée dans cette étude. Durant les périodes de floraison des cultures oléagineuses, les abeilles sauvages étaient étroitement associées aux habitats semi-naturels alors que les abeilles domestiques ont montré une nette préférence pour les cultures à floraison massive. La diversité des abeilles sauvages dans les habitats semi- naturels était 3-4 fois supérieure à celle observée dans le colza ou le tournesol. L'importance de certains facteurs écologiques clefs pour la diversité des abeilles, comme la richesse floristique locale et la quantité d'habitats semi-naturels dans le paysage, a été confirmée et quantifiée. Il a également été démontré que ces effets varient en fonction de la saison et de l'échelle spatiale. Ces résultats mettent en évidence les processus écologiques responsables des partons de diversité des abeilles à différentes échelles spatiales, et peuvent contribuer à optimiser la conception des mesures de conservation visant à promouvoir la diversité des abeilles dans les agrosystèmes intensifs. / Bees are essential pollinators for crops and wild plants, but theintensification of agricultural practices have contributed to a significantdecline in their abundance and diversity. To effectively protect andpromote the bee fauna in agroecosystems, a better knowledge of theirdiversity patterns is required. The over-arching objective of this thesiswas to determine the spatial and temporal patterns of bee diversity andfloral resource use in an intensive agricultural system in western France.A spatially extensive survey of foraging wild bees and honey bees returned45.040 individual records at the territorial scale (29.314 honey bees and15.726 wild bees), representing 192 species, i.e. nearly 20% of the speciesrichness reported at the national scale. The bee community wascharacterised by a large proportion of uncommon species (28.8 %) and bysignificant temporal and spatial variations of the diversity, especially atlocal scales up to 10-20 km2. The importance of semi-natural habitats forsustaining wild bee populations was highlighted in this study. Duringoleaginous crop flowering periods, wild bees were tightly associated withsemi-natural habitats while honey bees have shown a clear preference formass-flowering crops. The diversity of foraging wild bees was 3-4 timesgreater in semi-natural habitats than in oilseed rape or sunflower fields.The importance of some keystone ecological correlates of bee diversity,such as the local floral richness and the amount of semi-natural habitatsin the vicinity, has been confirmed and quantified. It was also evidencedthat their effect varies among seasons and spatial scales. These resultshighlight the ecological processes underlying bee diversity patterns atdifferent spatial scales, and further help to optimise the efficiency ofconservation measures intended to promote bee diversity in intensiveagrosystems.