A major challenge in agroecosystems is how to manage the systems so that it reduces crop pests and enhances natural pest control. This thesis investigates patterns of crop pests and top-down effects of birds and arthropod predators in relation to land-use composition across spatial scales. In paper (I) I examined the crop distribution and land-use types in relation to the crop raiding patterns in 15 transectsin sites close to and far from forests along with a questionnaire survey at household level. I found severe crop raiding close to forests, but it had no impact on crop composition growing between the two sites. In paper (II) I examined the effect of forest and tree cover, at local and landscape scales, on the abundance of arthropod predators by collecting specimens from 40 home gardens. My result showed higher abundance of arthropod predators when either the home garden or the surroundings had a high tree-cover, compared to when tree-cover at both scales was similarly either high or low. In paper (III) I investigated the effect of excluding birds and arthropod predators on leaf damage on rape seed in 26 home gardens. I found stronger top-down impacts from arthropod predators on crop pests in tree-poor gardens than in tree-rich gardens. There was no effect of birds. In paper (IV) I explored the effect of landscape complexity on bird and arthropod predation using plasticine caterpillars in 36 home gardens across landscapes. The rate of arthropod predation on caterpillars was higher in simple than in complex landscapes. The rate of bird predation did not vary between complex and simple landscapes. In simple landscapes, arthropod predation was higher than that of birds. The overall results suggest that simplified gardens/landscapes still have enough habitat heterogeneity to support arthropod predators for the significant top-down controlling effect on crop pests. However, I did not find clear effect of complexityon the top-down effect of birds. / <p>At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Manuscript; Paper 3: Manuscript; Paper 4: Manuscript</p>

Corn is one of the cereals most important, being cultivated in several countries in the world, has a fundamental role in human food and animal, and being it also indispensable in industry. However, the tendency to overcome the productivity of this is a constant challenge. Thus, the objectives of the present study were: characterize families S1, S2 and S3 from landrace corn as to phenological development, thermal demand and flowering synchrony; reveal effects of artificial defoliation in philological maturity on yield components of corn hybrids, in different plant populations. The study 1 (E1) was carried at the farm harvest 2015/2016 in the experimental area of the Universidade Federal de Santa Maria, Campus of Frederico Westphalen (UFSM-FW). For this, 34 segregating families were studied in different generations, belonging to from four populations of landrace corn (Planalto, Dente de ouro, Argentino amarelo and Argentino branco). For this, five commercial hybrids were used as controls. For the study 2 (E2) were used two simple hybrids DKB 240 VT PRO® e DKB 290 VT PRO®). The experiment was carried in the municipality of Redemption/RS, in the harvest 2014/2015, in a randomized block design in a factorial 2x2x2 (hybrids, defoliation and plant population). In E1, the families AAS1F1, DOS3F3, ABS2F2, ABS3F1, PLS1F1, PLS3F1, PLS3F2 and PLS3F3 had flowering synchrony. The duration of vegetative stages of families was relative to the quantity of leaves developed. The families with the high number of leaves demanded high thermal requirement to reach the flowering, indicating that more time is needed to develop a high number of source-organs to maintain a higher biomass. For the E2, the total defoliation in the physiological maturity negatively affects the yield components of the ear, reducing ear length (5.6), the kernel mass per ear (10.9), the ear mass (8.9) and the grain yield (9.5%). The increase in plant population has reduced the number kernel per row (14.4), the kernel weight (22), the kernel mass per ear (21.3), the thousand kernel weight (10.6), the kernel length (3.8), the kernel width (3.9) and grain yield (9.5%). Artificial defoliation in physiological maturity and high plant populations negatively influenced the main components of maize production. The DKB 290 VT PRO® hybrid presents superiority on kernel mass per ear (6.9), ear length (16.3) and kernel length (4%) in relation to DKB 240 VT PRO® hybrid. / O milho é um dos cereais mais importantes, sendo cultivado em diversos países no mundo, pois tem papel fundamental na alimentação humana e animal, sendo também indispensável para indústria. No entanto, a tendência de superar a produtividade deste cereal é um desafio constante. Dessa forma, os objetivos do presente trabalho foram: caracterizar famílias S1, S2 e S3 de milho crioulo quanto ao desenvolvimento fenológico, exigência térmica e sincronia floral; revelar os efeitos da desfolha artificial realizada durante a maturação filológica sobre os componentes de rendimento em híbridos simples de milho submetidos a diferentes densidades de semeadura. O estudo 1 (E1) foi conduzido na safra agrícola 2015/2016 na área experimental da Universidade Federal de Santa Maria, Campus de Frederico Westphalen (UFSM-FW). Para isto, foram estudadas 34 famílias segregantes em diferentes gerações, oriundas de quatro populações de milho crioulo (Planalto, Dente de Ouro, Argentino Amarelo e Argentino Branco). Para isso, cinco híbridos comerciais foram utilizados como testemunhas. Para o Estudo 2 (E2), foram utilizados dois híbridos simples (DKB 240 VT PRO® e DKB 290 VT PRO®). O experimento foi realizado no município Redentora/RS, na safra 2014/2015, em delineamento de blocos casualizados com esquema fatorial 2x2x2 (híbrido, desfolha e população de plantas). Em E1, as famílias AAS1F1, DOS3F3, ABS2F2, ABS3F1, PLS1F1, PLS3F1, PLS3F2 e PLS3F3 tiveram sincronia na floração. A duração dos estádios vegetativos das famílias foi relativo à quantidade de folhas desenvolvidas e as famílias com maior número de folhas demandaram maior exigência térmica para atingir a floração, indicando assim, que maior tempo é necessário para desenvolver maior número de órgãos fonte para atender uma maior biomassa. Para E2, a desfolha total na maturação fisiológica afeta negativamente os componentes de rendimento da espiga, sendo o comprimento de espiga (5,6), a massa de grão por espiga (10,9) e a massa de espiga (8,9) e o rendimento de grãos diminui (9,5%). O aumento na população de plantas reduziu o número de grãos por fileira (14,4), a massa de espiga (22), a massa de grãos por espiga (21,3), a massa de mil grãos (10,6), o comprimento de grãos (3,8), a largura de grãos (3,9) e o rendimento de grãos (9,5%). A desfolha artificial na maturação fisiológica e populações altas de plantas influenciaram negativamente os principais componentes de produção do milho. O híbrido DKB 290 VT PRO® foi superior com a massa de grãos por espiga (6.9), comprimento de espiga (16.3) e comprimento de grãos (4%) em relação ao híbrido DKB 240 VT PRO®.

In this thesis, I combined observational studies with field and greenhouse experiments to examine selection on life history traits and variation in tolerance and resistance against herbivores in natural populations of the annual herb Arabidopsis thaliana in its native range. I investigated (1) phenotypic selection on flowering time and plant size, (2) the effects of timing of germination on plant fitness, (3) the effect of leaf damage on seed production, and (4) correlations between resistance against a specialist and a generalist insect herbivore. In all three study populations, flowering time was negatively related to plant fitness, but in only one of the populations, significant selection on flowering time was detected when controlling for size prior to the flowering season. The results show that correlations between flowering time and plant fecundity may be confounded by variation in plant size prior to the reproductive season. A field experiment detected conflicting selection on germination time: Early germination was associated with low seedling survival, but also with large leaf rosette before winter and high survival and fecundity among established plants. The results suggest that low survival among early germinating seeds is the main force opposing the evolution of earlier germination, and that the optimal timing of germination should vary in space and time as a function of the relative strength of selection acting during different life-history stages. Experimental leaf damage demonstrated that tolerance to damage was lowest among vegetative plants early in the season, and highest among flowering plants later in the season. Given similar damage levels, leaf herbivores feeding on plants before flowering should thus exert stronger selection on defence traits than those feeding on plants during flowering. Resistance against larval feeding by the specialist Plutella xylostella was negatively correlated with resistance against larval feeding by the generalist Mamestra brassicae and with resistance against oviposition by P. xylostella when variation in resistance was examined within and among two Swedish and two Italian A. thaliana populations. The results suggest that negative correlations between resistance against different herbivores and different life-history stages of herbivores may contribute to the maintenance of genetic variation in resistance.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-05-22T15:55:42Z No. of bitstreams: 2 Tese - Leandro Maracahipes dos Santos - 2017.pdf: 3094765 bytes, checksum: a7fa8f585e1539956b511e26bdb50212 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-05-22T15:56:58Z (GMT) No. of bitstreams: 2 Tese - Leandro Maracahipes dos Santos - 2017.pdf: 3094765 bytes, checksum: a7fa8f585e1539956b511e26bdb50212 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-05-22T15:56:58Z (GMT). No. of bitstreams: 2 Tese - Leandro Maracahipes dos Santos - 2017.pdf: 3094765 bytes, checksum: a7fa8f585e1539956b511e26bdb50212 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-04-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The adoption of different ecological strategies is an important factor to determine the establishment and persistence of species in local communities. In general, the Cerrado is characterized by high fire frequency and poor soils. Generally under conditions of low fertility and high fire frequency the filtered species tend to have characteristics that represent adaptations to these environmental stresses. Considering that savanna species evolved under severe environmental filters, our aim was to evaluate how the adoption of different ecological strategies can determine the performance of the functional traits, the structure of the communities, and the relationship between a focal plant and its neighborhood. In this thesis work, which is divided into three chapters, we use three different scales to evaluate how species ecological strategies can determine the performance and establishment in local communities. In the first chapter, which is based on habitat scale, we evaluated how ecological strategies of generalist and specialist species of seasonal forest and savannas are fundamental for the establishment and persistence of the species in these habitats with marked differences in frequency in fire frequency and nutrient availability. In this chapter, we discuss that the different strategies adopted by species are in accordance to the limiting factors of the species occurrence in each of these environments. In the second chapter, which is based on community scale, we seek to understand how environmental gradients can determine different ecological strategies related to functional traits and density of individuals. We showed that the changes in trait values and density of individuals were more evident in the fertility gradient than toxicity, and that seasonal forest communities were more sensitive to changes savanna communities in both gradients. We also observed that species with conservative traits were associated with poor soils and species with acquisitive traits with more fertile soils. In the third chapter, which was developed at the individual scale, we discussed whether the characteristics and phylogenetic relationship of the neighboring plants influence leaf damage in trees and shrubs of savannas. In this chapter, we showed that the ecological and evolutionary distance between individual plants and neighboring plants does not determine the level of leaf damage by herbivores. We discussed that the dominance of generalist herbivores, co-evolution between plants and specialist herbivores, and preferential consumption of young leaves may be more important to determine the level of leaf damage than the neighboring context in which a given plant is inserted. / A adoção de diferentes estratégias ecológicas é um fator importante para determinar o estabelecimento e a persistência de espécies em comunidades locais. De maneira geral, o cerrado é caracterizado por uma alta frequência de fogo e solos pobres em nutrientes. Geralmente em condições de baixa fertilidade e alta frequência de fogo as espécies filtradas tendem a possuir características que representam adaptações a estes estresses ambientais. Considerando que as espécies de Cerrado se desenvolvem sob a atuação destes filtros ambientais, nosso objetivo foi avaliar como a adoção de diferentes estratégias ecológicas podem determinar a performance dos atributos funcionais, a estrutura das comunidades e a relação entre uma planta focal e sua vizinhança. Neste trabalho de tese, que está dividido em três capítulos, nós utilizamos três diferentes escalas para avaliar como estratégias ecológicas das espécies podem determinar seu desempenho e estabelecimento em comunidades locais. No primeiro capítulo que está baseado em uma escala de habitat, nós avaliamos como as estratégias ecológicas de espécies generalistas e especialistas de floresta estacional e cerrado sentido restrito são fundamentais para o estabelecimento e a persistência das espécies nestes habitats com diferenças marcantes em relação à frequência de fogo e disponibilidade de nutrientes. Neste capítulo, nós discutimos que as diferentes estratégias adotadas pelas espécies estão de acordo com os fatores limitantes da ocorrência de espécies em cada um destes ambientes. No segundo capítulo, que está baseado em escala de comunidades, nós buscamos compreender como os gradientes ambientais podem determinar diferentes estratégias ecológicas relacionadas aos atributos funcionais e a densidade de espécies. Nós demonstramos que as mudanças nos valores de atributos e densidade de espécies foram mais claras no gradiente de fertilidade do que toxicidade, e que comunidades de floresta estacional foram mais sensíveis a mudanças do que comunidades de cerrado sentido restrito em ambos os gradientes. Nós observamos também que espécies com atributos conservativos foram associados à solos pobres e espécies com atributos aquisitivos associado à solos mais férteis. Já no terceiro capítulo, que foi desenvolvido na escala de indivíduo, nós discutimos se as características e relação filogenética das plantas vizinhas influenciam o dano foliar em árvores e arbustos do cerrado. Neste capítulo, demonstramos que a distância ecológica e evolutiva entre plantas individuais e as plantas vizinhas não determina o nível de consumo foliar por herbívoros. Nós discutimos que a dominância de herbívoros generalistas, a co-evolução entre plantas e herbívoros especialistas, e o consumo preferencial de folhas jovens podem ser mais importante para determinar o nível de dano foliar do que o contexto de vizinhança em que uma dada planta está inserida.