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Made available in DSpace on 2015-04-22T22:12:38Z (GMT). No. of bitstreams: 1 Joao Paulo Machado de Araujo.pdf: 1095116 bytes, checksum: 1abc62db3a6c0e189fb12de4697e8f77 (MD5) Previous issue date: 2012-06-26 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ophiocordyceps are the main entomopathogenic fungi. They are highly virulent and may have an important influence on their hosts communities. In the present study, we collected ants of the genus Camponotus infected by fungi belonging to the complex Ophiocordyceps unilatera-lis sensu lato in three areas of the Brazilian Amazon. In Ducke Reserve, two samples were taken, one in the dry season of 2011 and another in the rainy season of 2012. In Parque Na-cional do Viruá and Estação Ecológica de Maracá, the samples were taken during one dry sea-son of 2012. Within each area, nine 250 m-long transects, at least 1 km distant from each oth-er, were sampled. We found 424 infected Camponotus by Ophiocordyceps in various stages of development. The infection rate in the rainy season was on average three times higher than the dry season, probably reflecting the survival and developmental needs of spores, however, even in the dry season there were infected. The infection rate was similar between the three areas despite differences in climate, vegetation and ant species composition. We found 17 Camponotus species infected, but we believe this number is even higher. Hyperpara-site occurrence rate was low, representing 6% of total infected ants found, suggesting little effect on Ophiocordyceps population in these areas. There was no relationship between the number of infected ants and the soil type (in terms of granulome-try). We found morphological differences among the spores infecting different species of ants, indicating that there are several species of the O. unilateralis not yet described, requiring fur-ther taxonomic studies to better understand this relationship. / Os Ophiocordyceps são os principais fungos entomopatogênicos, possuem alta virulência e podem ter grande influência nas comunidades de seus hospedeiros. No presente estudo, foram coletadas formigas do gênero Camponotus infectadas por fungos pertencentes ao complexo Ophiocordyceps unilateralis sensu lato em três áreas da Amazônia brasileira. Na Reserva Ducke foram realizadas duas coletas, uma na época mais chuvosa e uma na época mais seca. Nas reservas de Viruá e Maracá, as coletas foram feitas na época seca. Dentro de cada área, nove transectos de 250 metros foram amostrados, sendo estes, distantes no mínimo 1 km entre si. Foram encontradas 424 formigas Camponotus infectadas com o fungo em vários estádios de desenvolvimento. A taxa de infecção na época chuvosa foi em média 3 vezes superior à época seca, provavelmente em função das necessidades de sobrevivência e desenvolvimento dos esporos, entretanto, mesmo na época seca houveram formigas infectadas. A taxa de infec-ção foi semelhante entre as três áreas estudadas apesar das diferenças de clima, vegetação e composição de espécies de formigas. Foram encontradas 17 espécies de Camponotus infecta-das, mas acreditamos que este número seja ainda maior. A taxa de hiperparasitismo foi baixa, menos de 6% no total das formigas encontradas infectadas, bastante inferior a outros estudos, aparentemente afetando pouco a população de Ophiocordyceps unilateralis nessas áreas. Não encontramos influência da granulometria do solo sobre essas infecções. Foram encontrados diferentes tipos de esporos para diferentes espécies de formigas infectadas, indicando que há várias espécies diferentes entre os O. unilateralis ainda não descritos, sendo necessário estu-dos taxonômicos posteriores para um melhor entendimento desta relação.

Nitrogen (N) deposition in Europe has recently increased and is expected to continue to increase in the future. There is a well-documented decline in lichen diversity with higher N availability, although the mechanisms behind this are poorly known. In this study, I tested whether attacks by fungal parasites increase with higher N deposition. This pattern has been found in a number of studies on vascular plants, but it has never been investigated for lichens. I surveyed dark lesions and discolourings caused by fungi on the pollution-sensitive lichen Alectoria sarmentosa, after 4 years of increased N deposition in a whole tree fertilisation experiment in a boreal spruce forest. I found two species of fungi growing on the investigated lichen thalli. One of these species responded positively to increased N deposition. The results show that lichens can suffer from increased parasite attacks under a higher N load. Further studies using multiple lichen species and many years of recording are needed to understand the importance of parasites for the response of whole lichen communities to an increased N load.

The background to the large-scale planting of Pinus contorta in northern Sweden is reviewed with an account of the distribution and characteristics ofPi nus contorta within its natural range in western North America. The threatsto successful planting of exotics are discussed in relation to the historicalbackground. Attention is also drawn to parasitic fungi which are infectingPi nus contorta in western Canada, and to the potential threat they representto the indigenous Pi nus sylvestris in Sweden.During a seven-year-period 100 provenances of Pi nus contorta have been investigatedannually with respect to different kinds of damage, primarilythose by parasitic fungi. The study indicates that damage to Pi nus contortaprimarily occurs during the first ten years after planting. Northern provenancesof Pi nus contorta are generally more resistant to pathogens than southernprovenances. Weather damage occurs almost every year among trees ofsouthern and coastal provenance. Even trees of northern provenance have sufferedfrom weather damage due to temperature oscillations during shoot elongation.Severe weather damage is a predisposing factor to infection by secondarypathogens primarily.Gremmeniella abietina. There is a minor correlation betweensevere weather damage and Phacidium infestans. Even northern provenancesof Pinus contorta are infected by Phacidi um infestans in high altitude standsin northern Sweden. Snow b light infection is, however, of a minor importanceto lodgepole pine than to Scots pine due to the rapid early growth of the former.The most productive plants of both Pinus contorta and Pinus sylvestrisare attacked by Phacidi um infestans. Plants not infected by snow b light havea lower height growth than those infected.Severe infection by Gremmeniella abietina has been recorded after voleattack, even among northern provenances of lodgepole pine. So far Pinus contortahas mainly been infected by the same fungi as Pinus sylvestris, with the |exception of Melampsora pinitorqua and Lophodermella sul ci gena. Pinus contorta iis, however more susceptible to infection by Gremmeniella abietina in connec- !tion with vole damage, depending on the more severe injuries to lodgepole pinethan to Scots pine.So far vole damage has been the most severe threat to Pinus contorta innorthern Sweden. Voles prefer lodgepole pine to Scots pine providing vole populationis moderate. At times of high vole populations even Scots pine suffersdamage. Voles attack Pinus contorta even 14 years after planting. The differencein frequency of vole damage among provenances strongly decreased with increasedvole population and repeated attacks from year to year.Tree tilting was first noted five to eight years after planting on sites exposedto strong winds and severe icing.In the central parts of northern Sweden most provenances of Pinus contortaare less attacked by pathogens than the indigenous Pinus sylvestris, and inorthern provenances of lodgepole pine are remarkably productive in thenorthernmost site, despite a relatively high frequency of Phacidium infestar^.Later investigations indicate, however, more severe damage to Pinuscontorta with increasing latitude and altitude in northern Sweden. / digitalisering@umu

To date, few studies have focused on the effects of genetically modified trees (GM trees) on the environment. One concern with GM trees is that they may have unanticipated effects on non-target organisms, i.e. effects on organisms that are not direct targets of the genetically modified trait. The main objective of this thesis was to study potential non-target effects from the interaction between GM trees and natural enemies, including phytopathogens and herbivorous insects. To study this I used a system consisting of GM trees featuring changes in growth-related characteristics, and naturally occurring enemies. The GM trees used were the aspen hybrids Populus tremula x tremuloides: one unmodified wild type clone T89 (control) and transgenic lines with altered expression of gibberellin (GA 20-oxidase), sucrose (SPS) or pectin (PME); and Populus tremula x alba: one unmodified wild type clone INRA 717-1-B4 (control) and lines modified to suppress the activity of the enzymes in the lignin biosynthetic pathway, i.e. CAD, COMT, CCR or CCoAOMT. The natural enemies used were the parasitic phytopathogens Melampsora pinitorqua, M. populnea and Venturia tremulae, and the herbivorous leaf-beetle Phratora vitellinae. To address this question inoculation experiments, feeding preference experiments, analyses of secondary chemistry and field inventories were performed. The results of the studies showed that the GM trees significantly affected the interaction with the natural enemies, both in the laboratory as well as in the field. For instance, both M. pinitorqua and V. tremulae showed an altered disease incidence on the GM trees of P. tremula x tremuloides compared to the unmodified wild type T89, where all tested transgenic lines exhibited altered susceptibility to the pathogens. However, there were also differences in aggressiveness to the aspens depending on pathogen population. The results from the field inventory showed that lines within all tested transgenic construct, COMT, CAD, CCoAOMT and CCR of P. tremula x alba differed significantly from the wild type INRA 717-1-B4 in susceptibility to M. populnea. In addition, the susceptibility to the rust also differed significantly between lines carrying the same transgenic constructs. Furthermore, we found that overexpression of SPS in P. tremula x tremuloides, unintentionally induced changes in plant secondary chemistry, where the GM-line SPS33A exhibited the largest deviation from the wild type T89 in contents of plant phenolics and nitrogen, and that these changes coincide with a concurrent decrease in herbivory by P. vitellinae on this line. I argue that the altered interactions are the result of physiological changes in the trees. They can originate from direct effects i.e. altered expression of the modified trait, indirect effects of the genetic modification process e.g. pleiotropy, or effects from the transformation process e.g. position effects, to which the tested natural enemies respond. The result stresses the importance of further research on the causes and mechanisms responsible for the altered interaction between GM trees and non-target organisms, as well as evaluating the potential environmental effects of cultivation of GM trees in the field. Such research will require collaboration between researchers from different disciplines, such as plant ecology and physiology, functional genomics, proteomics and metabolomics.

All living organisms require food for growth and survival. Heterotrophs depend on autotrophs such as green plants which can synthesize their own food unlike heterotrophic animals. Among heterotrophs, only humans and some insects have the remarkable ability to cultivate crops for food. While humans cultivate plants, three insect lineages—ants, termites, and beetles—cultivate fungi inside their nests in obligate mutualistic exo-symbioses. Interestingly, just like human agriculture, insect fungus farms are also threatened by weeds and pests, e.g. the farms of fungus-growing termites which cultivate Termitomyces fungi can be overgrown by weeds such as the parasitic fungus Pseudoxylaria. Studies on ant and beetle fungus-farming systems have uncovered the important role of chemicals and behaviour in helping these insects to protect their crops from parasitic fungi. On the other hand, studies on the termite system till now, have only revealed the presence of antifungal compounds and actinobacteria which are largely non-specific and inhibitory to the mutualistic crop fungi. Antifungal behavioural mechanisms, if present, are yet to be discovered. Therefore, this thesis focuses on different anti-Pseudoxylaria mechanisms employed by fungus-growing termites, viz. role of nest abiotic factors, mechanism of fungal recognition by termite hosts, behavioural response of termite to Pseudoxylaria presence and coupling of this behaviour to anti-Pseudoxylaria activity. The present thesis has been divided into six chapters. CHAPTER 1 gives a brief literature review on fungus-farming insects and the different mechanisms which insects employ in order to keep their fungal farms safe from growth of parasitic fungi with specific reference to fungus-growing termites. The obligate mutualistic interaction between termites and the Termitomyces fungus is 19–49 My-old and is, therefore, a very ancient agriculture system. The mutualistic fungus is cultivated on partially digested plant matter called fungus comb inside the nest and harvested by termites for nutrition. At the same time, the weedy fungal parasite Pseudoxylaria can compete with the mutualistic fungus for nutrition leading to negative effects on the fungal farms. Termite hosts are believed to use abiotic factors, antibiotics and hygienic behaviours to keep their fungal gardens free from parasitic fungi such as Pseudoxylaria. However, the actual mechanisms used by termites against parasitic fungi are unclear. Unravelling the proximate mechanisms used in fungal cultivar protection is central to understanding the evolutionary stability of these farming mutualisms. CHAPTER 2 examines the diversity and population genetic structure of Termitomyces and Pseudoxylaria strains associated with the fungus-growing termite Odontotermes obesus. Genetic diversity of cultivar and parasite could have important implications for the stability of the mutualistic interaction, e.g. genetic clonality arising from monoculture is generally thought to make populations more prone to infection by parasites. Using molecular phylogenetic tools, within-nest genetic homogeneity was found in Termitomyces species but not in Pseudoxylaria species. Lower OTU but higher genotypic diversity (within the most abundant OTU) was found in the genus Termitomyces compared to Pseudoxylaria. Additionally, population genetics methods suggested a sexual population structure for Termitomyces and clonal propagation for Pseudoxylaria species. This is the first study to investigate the population genetics of the symbiotic fungi associated with the termite genus Odontotermes or any other termite species from India. In CHAPTER 3, the effect of nest micro-environment alone on the growth of the parasitic fungus Pseudoxylaria was examined. For this, seasonal changes in nest xiii temperature and CO2 were recorded and in situ and ex situ growth experiments were performed on Pseudoxylaria. The monthly pattern of mound temperatures was found to be similar to the outside—cycling from highs in summer to lows in winter—but characterised by dampened variation compared to high daily fluctuations outside. Moreover, the mound CO2 levels were found to be orders of magnitude above atmospheric levels and, unlike the outside, were characterised by daily and monthly fluctuations. With in situ experiments during summer and winter, the effect of these dissimilar conditions—inside and outside mounds—was examined on Pseudoxylaria growth. The growth of the parasite was found to be greater inside than outside the mound. Following this, the growth of different parasite isolates under controlled ex situ conditions was examined—spanning the variation in environmental conditions that mounds exhibit daily and seasonally. High CO2 levels decreased parasitic fungal growth in general but temperature had an isolate-dependent effect. Taken together, these results suggested that the parasite is adapted to survive in the mound. However, mound environmental conditions still seemed to exert a negative effect on parasite growth, even if they cannot inhibit Pseudoxylaria completely. These results shed light on the possible new role of termite-engineered structures in impacting parasitic fungus ecology, independent of any direct role of termites in suppressing parasite growth. This is the first study to investigate the effect of abiotic factors on Pseudoxylaria growth. In CHAPTER 4, whether termites can differentiate between Termitomyces and Pseudoxylaria was investigated. In a novel, laboratory-based choice assay, termites displayed a differential response towards the two fungi by burying the Pseudoxylaria with agar. Also, termites were found to be able to differentiate between the fungi using olfactory cues, i.e. smell, alone, for this task. The mutualistic and parasitic fungi were found to emit unique volatile bouquets which could help termites to distinguish between them. This is important because, whether termites use antifungal compounds or hygienic behaviours, it is crucial that they are able to differentiate between the parasitic and mutualistic fungi so that they can selectively use antifungal mechanisms—whether chemical or behavioural—against Pseudoxylaria. This is of special significance because, many actinobacteria and anti-Pseudoxylaria compounds isolated from this system till now, lack specificity and inhibit the mutualistic Termitomyces as well. Also, fungal grooming and weeding behaviours as displayed by fungus-growing ants have not yet been reported in termites. This is the first study to show that termites have the behavioural capacity to differentiate between the mutualistic and parasitic fungi in an ecologically relevant setting. In CHAPTER 5, whether the burying of Pseudoxylaria could affect its growth was investigated. It was found that termites can utilise agar, glass beads and soil for deposition over the offered fungal plugs but the use of agar and glass beads did not inhibit Pseudoxylaria growth effectively. On the other hand, soil deposition was found to decrease growth of both Pseudoxylaria and Termitomyces fungi post-burial. However, Pseudoxylaria was found to be affected more strongly than Termitomyces. Further, hypoxia acting alone seemed to decrease only Pseudoxylaria survival without any apparent effect on Termitomyces. Therefore, hypoxia induced by soil deposition may be the reason behind the decrease in Pseudoxylaria survival. However, presence of antifungal compounds can not be ruled out and they may be selectively applied in larger quantities on Pseudoxylaria with soil deposition. This study demonstrates an anti-Pseudoxylaria activity of this insect behaviour, unique to termites among fungus-farming insects, to the presence of the parasitic fungus. CHAPTER 6 concludes the findings of this thesis and suggests a working model for the mechanism of growth suppression of Pseudoxylaria inside a termite nest. In particular, focus is on the important role of abiotic factors when combined with termite behaviour in the apparent absence of Pseudoxylaria from termite nests. These results not only shed new light on how the ecology of these fungi is affected by their termite host but also reveal the mechanistic bases that may contribute fundamentally to the evolutionary stability of this ancient mutualism.

The fungal domain has one of the highest biodiversities among eukaryotes and species within the domain fill important ecological roles, such as mutualistic mycorrhiza, decomposers, parasites and pathogens. The development of forest ecosystems and their related processes has not only been linked to fungal diversity but the composition and abundance of fungi benefits the abundance and diversity of other species as well. In this study three questions concerning the differences in the fungal communities between mixed forests and coniferous forests were considered. Inventories were done in coniferous forest and mixed forest areas classified as nature reserves and later statistically analyzed. The study could show that while the probability of finding ectomycorrhiza was significantly higher in mixed forests than coniferous forests, the probability of finding saprotrophs was significantly higher in coniferous forests than in mixed forests. Results in contrast to other studies were also found. The study revealed that more is needed to be done on the topic of forest fungi in mixed forest and coniferous forest areas. / Svampdomänen har en av de högsta biologiska mångfalderna bland eukaryoter och domänens arter innehar viktiga ekologiska roller, såsom mutualistisk mykorrhiza, nedbrytare, parasiter och patogener. Utvecklingen av skogsekosystem och deras relaterade processer har inte bara kopplats till svampdiversitet utan svamparnas sammansättning och förekomst gynnar också förekomst av och mångfald hos andra arter. I denna studie behandlades tre frågor om skillnaderna i svampsamhällen mellan blandskogar och barrskogar. Inventeringar gjordes i barrskogs- och blandskogsområden klassificerade som naturreservat och analyserades senare statistiskt. Studien kunde visa att även om sannolikheten för att hitta ektomykorrhiza var signifikant högre i blandskogar än barrskogar, var sannolikheten för att hitta saprotrofer signifikant högre i barrskogar än i blandskogar. Resultat i motsats till andra studier hittades också. Studien visade att det behövs mer forskning om skogssvampar i blandskog och barrskogsområden.

Understanding of carbon cycling in coniferous forests that represent a large carbon sink is crucial for our understanding of natural processes under global climate change. Recognition of fungi as fundamental decomposers can contribute to this understanding. Fungi are able to decompose numbers of substrates and possess a variety of enzymes to do so In this study I present litter decomposing fungi in mountain spruce forest from national park Šumava. The aim of my thesis was to follow succession and community changes of fungi from the early stages of decomposition of Picea abies needles until degradation of organic matter in the organic horizon of the soil. This aim was accomplished partly by recording the extracellular enzyme production of fungi in different stages of decomposition from needles attached to the twigs of a fallen tree to a litter material in later stages of decomposition on the soil surface. In addition to testing of fungi on their natural substrata - needle litter, enzyme activities were also measured in laboratory agar cultures, which allow comparison of diverse fungi with different origins. Enzyme activities were aimed at enzymes decomposing cellulose and compounds found in litter. Although ecology of endophytic and saprothrophic fungi suggest differences in enzyme production, these...