Many regional and local factors can influence the distribution of native and exotic species in ecological communities. I examined the regional- and local-scale determinants of native and exotic vascular plant species richness and composition in a highly fragmented oak savanna ecosystem on southeastern Vancouver Island. In sharp contrast to most reported results, I found a negative relationship between native and exotic richness at the regional scale, and no relationship at the local scale. Two extrinsic factors, surrounding road density and climate, best explained the regional-scale relationship by each affecting natives and exotics in opposite ways. Road density and climate were also the dominant predictors of native and exotic composition at the regional scale. Patterns in the patch occupancy of individual species confirmed the importance of these factors but I found that low surrounding road densities and cool, wet conditions predicted the presence of many natives and the absence of many exotics. Environmental factors explained variation in richness and composition at the local scale, but these factors were different for natives and exotics. My results suggest that natives and exotics respond to roads and climate in fundamentally different ways. Roads increase both exotic propagule pressure and disturbance, which may facilitate exotic invasion. In contrast, disturbance from roads may increase the likelihood of local extinction for particular natives. Differing climatic preferences within the native and exotic species pools may also partially explain the observed patterns. There was no evidence that native diversity directly affects exotic diversity (or vice versa). Surprisingly, I found that connectivity was not an important predictor of richness or composition despite the high degree of habitat fragmentation in this ecosystem.

Landnutzungsänderungen, Habitatverlust und Fragmentierung gehören zu den Hauptursachen des weltweiten Biodiversitätsrückgangs. In Mitteleuropa zählen Kalkmagerrasen zu den artenreichsten Lebensräumen. Sie weisen eine hohe Vielfalt an xero- und thermophilen Pflanzen- und Invertebratenarten auf, sind jedoch zunehmend durch landwirtschaftliche Intensivierung und Nutzungsaufgabe gefährdet. Sie sind auf Beweidung und Mahd angewiesen, was jedoch für die Landwirte heutzutage unwirtschaftlich geworden ist. Daher finden sich zunehmend kleine Fragmente innerhalb einer für die meisten der spezialisierten Magerrasenarten ungeeigneten, von intensiver Landwirtschaft geprägten Umgebung. Der erste Teil dieser Arbeit untersucht den Einfluss der Fragmentgröße, der Habitatkonnektivität, der Zusammensetzung der umgebenden Landschaft und der Pflanzenartenzahl auf die Zusammensetzung der Zikadengemeinschaft. Zikaden sind eine überaus artenreiche Gruppe phytophager Insekten mit enger Bindung an die Vegetationsstruktur und -zusammensetzung. In der Umgebung von Göttingen wählten wir 14 große (>1 ha) und 14 kleine (<1 ha) Kalkmagerrasenflächen entlang von Gradienten zunehmender Konnektivität mit anderen Magerrasenflächen, zunehmender Pflanzenartenzahl und zunehmender Landschaftskomplexität, d.h. dem Prozentsatz Ackerfläche innerhalb eines 500 m-Radius, aus. Zunehmende Isolation verringerte die Zikadenartenzahl in einfachen (von Feldern geprägten), jedoch nicht in komplexen Landschaften. Dieser Effekt wurde von den Generalisten getrieben. Die Artenzahl der Generalisten nahm auf kleinen Fragmenten mit zunehmender Konnektivität zu, wogegen sie auf großen Flächen unverändert blieb. Weiterhin nahm die Artenzahl der Generalisten mit steigender Pflanzenartenzahl auf vernetzten Magerrasen stärker zu als auf unvernetzten. Unsere Ergebnisse zeigen, dass die Insektenartenvielfalt auf Kalkmagerrasenfragmenten nicht nur durch Konnektivität allein geprägt wird, sondern vielmehr von einem Zusammenspiel aus Konnektivität, Landschaftszusammensetzung und Pflanzenartenzahl bestimmt wird. Im zweiten Teil dieser Arbeit verfolgen wir das Ziel, zur Lösung der sogenannten SLOSS-Debatte (“Single Large Or Several Small”) beizutragen, in der diskutiert wird, ob es besser ist, wenige große oder mehrere kleine Fragmente eines Habitattyps zu erhalten. Man nimmt an, dass kleine Fragmente aufgrund der größeren abgedeckten geographischen Distanzen eine größere Heterogenität und dadurch eine höhere Gesamtartenzahl aufweisen. Dagegen weisen große Fragmente stabilere Lebensraumbedingungen und größere Populationen auf. Neben Zikaden und Pflanzen wurden auch Daten zu Wanzen und 114 Schnecken aufgenommen. Sowohl die Gesamtartenzahl aller vier Taxa als auch die Zahl der Spezialisten war auf mehreren kleinen Fragmenten wesentlich höher als auf einem oder zwei großen Fragmenten gleicher Gesamtgröße. Jedoch war die Artenzusammensetzung auf großen und kleinen Fragmenten unterschiedlich und einige der seltensten Spezialisten waren an große Flächen gebunden. Hingegen spielte die Zusammensetzung der umgebenden Landschaft keine wichtige Rolle für Artenzahl und -zusammensetzung. Diese Ergebnisse stellen den Fokus auf entweder große oder kleine Habitatfragmente infrage. Für einen erfolgreichen Biodiversitätserhalt ist daher der Schutz sowohl großer als auch kleiner Habitatfragmente zwingend notwendig. Im dritten Teil dieser Arbeit untersuchen wir den Einfluss der Bewirtschaftungsart (Beweidung, Mahd, Nutzungsaufgabe), der Landschaftszusammensetzung und Konnektivität auf die Artenzahl, Artenzusammensetzung und merkmalsbasierte Reaktionen (Körpergröße und Rote Liste-Status) von neun Taxa: Pflanzen, Schmetterlinge, Bienen, Heuschrecken, Schwebfliegen, Spinnen, Wanzen, Kurzflügler und Zikaden. Wir wählten 30 kleine Kalkmagerrasenfragmente (<1 ha) entlang von unabhängigen Konnektivitäts- und Landschaftskomplexitätsgradienten aus. Ein zunehmender Prozentsatz an Ackerfläche in der Umgebung der Fragmente führte zu einem Verlust von 29 % der Gesamtartenzahl. Wir nehmen an, dass Landschaften, die von Ackerfläche dominiert werden, weniger Alternativhabitat und Nahrungsressourcen bieten, was zu einer verringerten Artenzahl führt. Habitatkonnektivität erhöhte im Allgemeinen die Artenzahl. Dieser Effekt war bei den großen, vermutlich ausbreitungsfähigeren Arten eines Taxons stärker ausgeprägt als bei den kleinen Arten. Beweidung hatte einen deutlich negativeren Einfluss auf die Artenzahl als Mahd (einmal jährlich) oder kurzzeitige Nutzungsaufgabe (5-15 Jahre). Der Grund dafür könnte der durch Beweidung verursachte größere Schaden und die Entnahme der Nahrungsressourcen phytophager Insekten sein. Zudem führte jeder der drei Bewirtschaftungsweisen zu einer unterschiedlichen Artenzusammensetzung aller Taxa. Daher sollte die bevorzugte Bewirtschaftungsoption kleiner Kalkmagerrasenfragmente ein Wechsel zwischen Mahd und kurzzeitiger Nutzungsaufgabe in Kombination mit einer Diversifizierung der umgebenden Landschaft sein. Zusammenfassend lässt sich sagen, dass die allgemein verbreitete Konzentration auf große Habitatfragmente überdacht werden sollte, da der Schutz sowohl kleiner als auch großer Fragmente unerlässlich ist. Bei der Planung von Schutzmaßnahmen für fragmentierte Offenlandlebensräume sind lokale Einflüsse wie Fragmentgröße und Bewirtschaftung zwar wichtig, aber nicht ausreichend: Landschaftsfaktoren wie Habitatkonnektivität und Landschaftszusammensetzung müssen ebenfalls in die Schutzbemühungen mit einbezogen werden um das langfristige Überleben von spezialisierten Pflanzen- und Invertebratenarten zu sichern.

Rain forest canopies are renowned for their very high biodiversity and the critical role they play in key ecological processes and their influence on global climate. Despite that New Zealand supports one of the most diverse and extensive epiphyte flora of any temperate forest system, few studies have investigated epiphyte communities and their invertebrate fauna along with factors that influence their distribution and composition. This thesis represents the first comprehensive study of entire epiphyte communities and their resident invertebrate fauna in the canopy of New Zealand’s indigenous forests. The aim of this study was to determine spatial patterns of epiphyte and invertebrate species richness, abundance and community composition in relation to abiotic variables, and in particular, the responses of these communities to elevated temperature and rainfall. This study was carried out in coastal lowland podocarp-broadleaved forests at two sites on the West Coast of the South Island of New Zealand. Samples from 120 mat-forming epiphyte assemblages located on inner canopy branches of 40 northern rata (Metrosideros robusta) trees were studied to characterise the component flora and fauna. Additionally, biomass, branch and tree characteristics and community responses to treatments designed to elevate temperature and rainfall to simulate predicted climate change were measured. This investigation revealed astonishing diversity and functional complexity of epiphyte and invertebrate life in this ecosystem. The 30.6 kg (dry weight) of epiphyte material collected contained a total of 567 species, 170 epiphyte and 397 invertebrate (excluding immature specimens and mites) species, including at least 10 species new to science and many undescribed species Epiphyte communities were found to be dominated by non-vascular plants (80 % of the total species richness), particularly liverworts and invertebrate communities were dominated with respect to abundance (~ 80 % of the total individuals) by Acari, Collembola and Hymenoptera (primarily ants) and functionally by scavengers and ants. Epiphyte and invertebrate communities were highly variable with respect to spatial patterning of species richness, abundance and composition across sites, among trees within sites and among branches within trees. Overall, a highly significant proportion, > 75 %, of the variance could be attributed to differences at the branch level, but these differences could not be explained by the environmental factors measured. There were no consistent relationships between the spatial pattern of epiphytes and invertebrates, or between vascular and non-vascular plants. However, there were significant positive correlations between epiphyte biomass and invertebrate species richness (r = 0.472; p < 0.0001) and abundance (r = -0.395; p < 0.0001), as well as non-living epiphyte biomass and scavenger species richness (r = 0.4; p < 0.0001). Microclimatic measurements taken on epiphyte mats were also highly variable with respect to temperature and relative humidity at similar physical locations within the same tree as well as across trees within sites. There was also considerable variation in the intensity and frequency of climatic extremes, although potentially harmful climatic conditions were experienced by all the epiphyte mats for which weather variables were measured. Negative correlations existed between both epiphyte and invertebrate community composition and increased temperatures expressed as cumulative degree days above 5˚C. However, variability was such that there was no direct evidence that increased temperature and rainfall treatments had an effect on invertebrate species richness, abundance or diversity. Northern rata host trees harbour an astonishingly diverse and complex canopy flora and fauna that is characterised by high spatial variability. Such variability highlights that to determine species distribution and community dynamics in canopy habitats in response to disturbance caused either by climate change or invasive species the structure of entire communities at different taxonomic and spatial scales, along with their responses to microclimatic factors, need to be studied. If such complexities are not taken into account, inappropriate interpretation may result in poor decisions concerning the conservation status, vulnerability and subsequent management of such unique ecosystems.

Em uma parcela permanente de 10,24 ha na Floresta Pluvial Atlântica Submontana do Parque Estadual Carlos Botelho (Sete Barras, SP, Brasil), este estudo teve o intuito de descrever o regime de distúrbio do dossel e avaliar a regeneração natural sob diferentes regimes de luz. Para tanto, foi realizado o levantamento de todas as clareiras da parcela, que foram mensuradas e tiveram sua idade aproximada estimada. Em seguida, foram instaladas 42 parcelas de 10x10m para avaliar a regeneração natural em três regimes luminosos: dossel contínuo (18 parcelas), clareiras pequenas a médias (11) e clareiras grandes com abundância de Guadua tagoara (Nees) Kunth (13). O regime de luz foi caracterizado por fotografias hemisféricas tomadas ao centro das parcelas. O estudo da regeneração natural foi divido em: estrato herbáceo (i.e., ervas menores que um metro de altura), avaliado através da cobertura do solo estimada pelo método de interceptação de linha; e estrato arbustivo, avaliado através dos indivíduos com altura maior que 1m, e com diâmetro à altura do peito menor que 5cm. Para estes indivíduos anotou-se a espécie, diâmetro, altura total e área de copa, além da presença de partes reprodutivas e substrato de germinação. Informações sobre hábito, grupo sucessional e síndrome de dispersão das espécies também foram obtidas. Após um ano, uma reavaliação permitiu analisar a mortalidade, danos, recrutamento e crescimento. Apesar de 67% das clareiras terem sido menores que 150 m2 , o regime de distúrbio foi atípico, principalmente pela contribuição de clareiras maiores que 750 m2 , e pela área média e total que variaram respectivamente de 419 a 799 m2 , e de 26 a 49%, dependendo do método de delimitação de clareira. A densidade foi de 6 clareiras.ha -1 e a taxa de recorrência variou entre 91 e 220 anos, dependendo dos métodos. Houve diferença significativa entre os ambientes para a maioria dos índices de luz, especialmente para a radiação total incidente com médias entre 909 e 2.400 mols.m-2.ano-1. Observou-se diferença significativa entre ambientes na cobertura por ervas, porém os resultados variaram entre espécies. No estrato arbustivo, houve diferença significativa na composição e abundância das espécies, inclusive entre clareiras médias e sub-bosque. A densidade de ervas e arbustos foi maior nos ambientes mais iluminados, assim como a densidade de pioneiras e secundárias iniciais. O recrutamento em um ano (16%) apresentou diferenças nos ambientes, com 63% dos recrutas apenas nas grandes clareiras. O mesmo não ocorreu com a taxa de mortalidade cujas principais causas foram os danos físicos e dessecamento. Para os 13% de indivíduos danificados em um ano, houve destaque para danos ligados à extração de palmito. Apenas os danos físicos naturais apresentaram diferença entre ambientes, com grandes clareiras sendo as mais danosas. No geral e entre as 25 espécies avaliadas separadamente, houve uma tendência de crescimento maior com o aumento da incidência luminosa. Clareiras pequenas a médias tiveram significativamente maior riqueza, diversidade e menor dominância de espécies que o sub-bosque. Clareiras grandes com bambu tiveram menor riqueza e diversidade, mas contribuíram com a manutenção da diversidade beta da parcela permanente. / In a 10.24 ha permanent plot of Tropical Lower Montane Atlantic Rain Forest in the Carlos Botelho State Park (Sete Barras, SP, Brazil), this study aimed to describe the canopy disturbance regime and to assess natural regeneration under different light regimes. In order to do so, the plot was completely surveyed for canopy gaps that were measured and had their approximate age estimated. Then, 42 10x10 m plots were established to evaluate natural regeneration under three light regimes: understory (18 plots), small to medium canopy gaps (11 plots) and large gaps abundant in Guadua tagoara (Nees) Kunth (13 plots). The light regime was characterized through hemispherical photographs taken at each plot center. Natural regeneration was dived into: herb stratum (i.e., herbs below one meter in height) assessed through soil coverage using the line intercept method; and shrub stratum or all plant individuals taller than one meter high and thinner than 5 cm in diameter at breast height. All individuals were identified to species and measured for diameter, height, crown height and area, besides notes on the presence of reproductive structures and germination substrate. Information on growth form, dispersal syndrome and ecological group were also obtained for each species. After one year, one reevaluation was made to assess mortality, damages, recruitment and growth. Although 67% of gaps were smaller than 150 m2 , the plot disturbance regime was atypical mainly by the contribution of gaps bigger than 750 m2 and by the average and total gap area that varied respectively from 419 to 799 m2 , and from 26 to 49% depending on the gap delimitation method. Gap density was 6 gaps.ha-1 and the turnover rate varied from 91 to 220 years depending on the gap method employed. There was significant difference between environments among the light index, especially for total incident radiation with means varying from 909 and 2,400 mols.m-2.y-1. It was found significant differences on herb soil coverage between environments, although the results varied among species. In the shrub stratum, species composition and abundance was significantly different, even between small to medium canopy gaps and the understorey. Herb and shrub densities were bigger in the more enlightened environments, as well as pioneer and early secondary species densities. Recruitment over the year (16%) was different between environments with large gaps accounting for 63% of all recruits. Similar difference was not found for mortality rate that had physical damage and desiccation as main death causes. Amid the 13% of damage individuals in the course of one year, there was noticeable contribution of damages linked to illegal extraction of palm-heart. Differences between environments were present only for physical damages with large gaps being the most damaging environment. In general and among the 25 species evaluated separately, there was a tendency of bigger growth with enhancement in light incidence. Small to medium gaps had significantly higher species richness and diversity, and lower dominance compared to the understorey. Large gaps had lower richness and diversity, but they contributed to maintain beta diversity of the permanent plot.

Made available in DSpace on 2015-03-26T13:30:53Z (GMT). No. of bitstreams: 1 texto completo.pdf: 986817 bytes, checksum: e4ef3e7967a1c4ddb759b319e3255b70 (MD5) Previous issue date: 2006-07-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The longitudinal distribution of adult Odonata was examined in streams of different channel width in the Pindaíba River Basin, in the municipalities of Barra do Garças and Nova Xavantina. The general purpose was to evaluate the existence of environmental gradients that affect the longitudinal distribution of Odonata, and to establish testable predictions to this predator group regarding the River Continuum Concept. Two hypotheses were tested: (1) increasing channel width longitudinally along the basin causes an increase of light input, and, assuming restraints and distinct abilities, there would be a decrease of Zygoptera and increase of Anisoptera species richness. (2) Dragonflies are affected by the gradient generated through river continuum mechanisms, increasing species richness in medium-sized streams. I sampled 19 sites in rivers and streams from 1st to 6th orders, and in each site I sample once in the dry and once in the rainy seasons. Quantitative survey was conducted through scan method in fixed areas, counting visually on Odonata adults along 100 meters of the waterbody, divided into 20 stretches of 5 meters each. Channel width and depth measures were taken at the beginning, middle, and end of each 20-meter region. A total of 549 individuals were collected, distributed in one family, 13 genera and 17 species of Anisoptera, and six families, 15 genera and 30 species of Zygoptera. The abundance and proportion of Zygoptera species decrease while Anisoptera increase with channel width and mean depth of rivers and streams. The channel width was considered the best predictor of Odonata species distribution. The distribution of Odonata, species richness, did not corroborate the hypotheses of higher species richness in the middle courses of streams. The results obtained in this study confirm the thermoregulation hypothesis as a determining factor in the distribution of Odonata species in the system. / A distribuição longitudinal de Odonata adultos foi avaliada em riachos de diferentes larguras na Bacia do Rio Pindaíba nos municípios de Barra do Garças e Nova Xavantina-MT. O objetivo geral foi avaliar a existência de gradientes ambientais influenciando a distribuição longitudinal de Odonata, estabelecendo predições testáveis para o grupo predador sobre o Conceito de Continuum fluvial. Foram testadas duas hipóteses: (1) o aumento da largura do canal longitudinalmente na bacia causa um aumento da entrada de luz e, assumindo restrições e habilidades distintas, haveria uma diminuição da riqueza de espécies de Zygoptera e aumento da riqueza de Anisoptera. (2) as libélulas respondem ao gradiente gerado pelo mecanismo do continuum fluvial, aumentando de riqueza nos riachos de tamanho intermediário. Foram amostrados 19 trechos em oito rios e riachos de 1a a 6a ordem, sendo que em cada um dos trechos foram efetuadas duas coletas, uma na estação seca e outra na estação chuvosa. A amostragem quantitativa foi feita pelo método de varredura com áreas fixas que consistiu na contagem visual do número de adultos em 100 metros do corpo d água, divididos em 20 segmentos de cinco metros. As medidas de largura e profundidade do canal foram tomadas no início, meio e final de cada segmento de 20 metros. Um total de 549 indivíduos foi coletado, pertencentes a uma família, 13 gêneros e 17 espécies de Anisoptera, e seis famílias, 15 gêneros e 30 espécies de Zygoptera. A abundância e a proporção de espécies de Zygoptera diminuem enquanto as de Anisoptera aumentam em relação à largura e a profundidade média dos rios e riachos. A largura foi considerada o melhor preditor da distribuição de espécies de Odonata. A distribuição de Odonata, considerando agregadamente Zygoptera e Anisoptera, não corrobora a hipótese de maior riqueza nos trechos médios dos riachos. Os resultados desse estudo suportaram a hipótese de termorregulação como fator determinante da distribuição das espécies de Odonata no sistema.

No description available.

Biological invasions are reportedly one of the major contributory factors to biodiversity loss worldwide. The impacts of invasive alien plant (IAP) species on native communities are widely documented in the scientific literature, however, there is still a lack of detailed information on their impacts within the most vulnerable habitats. Riparian habitats are highly dynamic systems and naturally disturbed, making them particularly vulnerable to invasion. Climate change, directly or indirectly, is also predicted to adversely impact river systems, which may subsequently alter invasion rates and the impacts of IAPs. However, the interactions between climate and IAPs and their combined effects on vegetation have rarely been examined. To address these knowledge gaps, this thesis investigates: (1) the role of environmental variables, such as sediment loading or climate-related changes to river flow regime, on the abundance of IAPs within riparian zones; (2) how variation in IAP abundance impacts native vegetation, relative to the effects of native dominant plant species and (3) some of the mechanisms underlying the effects of IAPs in riparian habitats. Historic and recent field survey data were used to investigate changes in riparian vegetation on British rivers during the last 20 years. Analyses indicate that IAPs had a negative but small effect on native plant diversity. Overall, changes in land use and differences in flow regime between recording periods were the most important predictors of plant community change. Specifically, IAPs had a greater probability of being present along lowland rivers that experienced increased frequency of high flow events. On a local scale across rivers in Scotland, the abundance of IAPs was constrained by greater soil moisture in summer, whilst greater abundance was associated with tree-lined banks. Both native dominant species and IAPs negatively affected subordinate species abundance to a greater extent than species richness, although this effect varied spatially with bank elevation. Artificial turf mats were used to quantify viable propagules within riverine sediment deposited over-winter along invaded riverbanks. The data indicate that there is a legacy effect of IAP abundance, with the most invaded sites being associated with higher sediment loading the following year, though, contrary to the general pattern, 12 sediment associated propagules were scarcer at invaded sites. Moreover, lower above-ground native diversity was associated with sites which had been previously invaded. Plant species composition in the propagule bank and above-ground vegetation were highly dissimilar, particularly closest to the water’s edge at highly invaded sites. This suggests that mono-specific stands of IAPs proliferate best under less disturbed environmental conditions, although fluvial disturbance events may be required to create opportunities for initial establishment. The propagule bank contributed very little to the above-ground vegetation, nor did it limit invasion, suggesting that above-ground plant composition is largely dictated by competitive interactions. The findings presented in this thesis suggest that invasion by IAPs is an additional stressor for native vegetation within riparian habitats, modifying above-ground plant communities via competition and suppressing recruitment from the propagule bank. However, native dominant species common in riparian habitats also negatively impact, subordinate species via competition, in some cases equalling the effect of IAPs. Native dominant and IAP species are differently affected by environmental factors operating in the riparian zone, which may provide future opportunities for reducing and managing invasions.

The savanna woodlands of Southern Africa, colloquially termed the miombo, are poorly described in terms of biodiversity compared to other biomes. They have therefore been underrepresented in the wider understanding of how land use intensification is shaping global biodiversity. Land use change is known to reduce biodiversity and disrupt intactness of ecological communities with consequences for ecosystem functioning, resilience, and services. Miombo woodlands are described as biodiversity hotspots due to a high endemism of species and the presence of megafauna. At the same time, they are also considered dynamic socio-ecological systems shaped by disturbances and the land use activities of people. The patterns of biodiversity change in these tropical ecosystems may, therefore, have their own unique contexts, understanding of which will be essential for biodiversity and land use management in these ecosystems. In this thesis, I identified the patterns of biodiversity change in response to the two major land use practices in the two dominant woodland types in southern African woodlands: the selective logging due to charcoal production in the mopane woodlands, and agricultural expansion in the miombo. I also examined the impact of two main disturbance agents, humans and elephants, on habitat structure and biodiversity in mopane woodlands. Across all chapters in this thesis, I investigated the effects of land use change and habitat modification on biodiversity empirically using chronosequences. To understand biodiversity change, I employed a hierarchical multilevel modelling approach making inferences at the three levels of ecological communities: species, community, and meta-community (set of ecological communities at different sites). I selected six villages in the charcoal production hotspot of southern Mozambique and carried out field surveys for three taxonomic groups: trees, mammals and ground beetles. I modelled the counts of trees and beetles and incidence of mammals using meta-community occurrence models in a Bayesian framework with the intensity class of the villages, above-ground biomass and land cover type as predictors. The results suggested that the species richness of trees and mammals declined by 12 and 8.5 % respectively while that of beetles increased by 3.5%, albeit non-significantly. In addition, the beta diversity of trees decreased while that of mammals increased. The results show that while both trees and mammals reduced in richness, they responded differently to charcoal production in terms of community organisation. The trees underwent subtractive homogenisation (decrease in alpha and beta diversities) primarily because of deterministic processes induced by selective harvesting of tree stems for charcoal. Mammal communities, on the other hand, showed subtractive heterogenization (decrease in alpha, but increase in beta diversity) mainly due to random extinctions. In the agriculture frontier of miombo-dominated northern Mozambique, I investigated the effects of fragmentation and habitat loss caused by agricultural expansion on diversity and composition of trees and mammals. I modelled the occurrences of trees and mammals using occupancy models with the fragmentation and quantity of woodland cover as predictors. The model showed that most tree species (n=10), mainly the timber and firewood species, linearly declined in population size as fragmentation increased. Mammals, on the other hand, showed a nonlinear response. Seven mammal species increased at the lower levels of fragmentation. However, at the higher levels, none of the mammal species increased while two declined. Similarly, the species richness of trees linearly declined, while that of mammals increased up to a fragmentation level of 55-65% and declined above this limit. The beta diversity of trees increased with fragmentation while that of mammals decreased. The results suggest that, although fragmentation reduces species richness of both trees and mammals, it affects their species compositions in different ways. Trees undergo subtractive heterogenization due to random species losses while mammals experience subtractive homogenisation mainly due to the combined effects of fragmentation-led habitat loss and intensified hunting. Finally, this study concludes that, above 75% fragmentation or below 26% habitat quantity, both taxonomic groups endure biodiversity loss. The threshold results here corroborate similar habitat quantity thresholds (20-30%) observed elsewhere in different ecosystems. However, they differ with the widespread notion that above 30% habitat quantity, the effect of fragmentation is non-existent. The results here emphasize that taxonomic groups respond differently, the diversity and population size of mammals reduced only after the habitat threshold, whereas, those of trees showed linear decrease with fragmentation most likely due to fragmentation-led habitat loss. Lastly, I examined the effects of disturbance by humans and elephants on habitat structure and bird diversity by conducting a space for time substitution comparison in the mopane woodlands of Zambia. To examine the woodland structure, I modelled the structural attributes of habitat (stem diameter, stand density, and basal area) using mixed models with the proportion of affected stems by humans and elephants as explanatory variables. I found that elephant disturbance was associated with higher stem diameters, low stand densities, but no change in basal area. Human disturbance, on the other hand, was related to reductions in stand density and basal area, but no change in the stem diameter. Further, I tested species and functional diversity of birds against the covariates of habitat structure and disturbance. I found that bird communities reduced in species richness in both, human as well as elephant disturbed areas. However, the functional diversity did not change with elephant disturbance. I concluded that human disturbance reduces woody biomass (basal area is correlated with woody biomass) of mopane woodlands and functional diversity of birds whilst elephants do not. In this thesis, I conclude that human driven land use change in the miombo woodlands erodes alpha diversity of all taxonomic groups. However, increases in beta diversity of mammals with charcoal land use and trees in agricultural land use may maintain their diversities at the meta-community level.

Made available in DSpace on 2016-06-02T19:31:49Z (GMT). No. of bitstreams: 1 2941.pdf: 567635 bytes, checksum: 18b3f5d53030b198ba538da511d6b2e3 (MD5) Previous issue date: 2010-03-02 / Universidade Federal de Minas Gerais / Together with fire and climate changes, soil is considered a major determinant in the Braziliancerrado, the richest savanna in the world. Soil can influence plants by filtering species capableof acquiring resources and compete for them, but can also influence plant patterns ofallocation in defense against herbivory. Although many studies focused on plant soilrelationship in cerrado, few focused on the influence of soil at fine scale. We expectedcommunity descriptors, such as floristic composition, richness, evenness, diversity, and totalabundance to be related to soil features at fine scale within a physiognomy. We also expectedplants on nutrient-poor soils to present higher anti-herbivory defenses. In a cerrado site, weplaced 100 contiguous 25 m2 plots, in which we identified all woody individuals, measuredsoil variables and the following leaf traits: specific leaf area, C:N ratio, water content,toughness, trichomes, latex, and presence of tannins, alkaloids, and terpenoids. We did apartial redundancy analysis to test for relationship between soil features and floristiccomposition, controlled for spatial dependence. We also did multiple regression or spatialautoregressive models to test for relationships between soil features and: (1) the abundance ofthe five commonest species, (2) total abundance, (3) richness, (4) evenness, and (5) diversityand to predict defense traits based on soil features. We found no relationship between soil andfloristic composition, probably due to functional redundancy or limited dispersal. Organicmatter was positively related to Myrsine umbellata, the most abundant species, and totalabundance, and negatively related to evenness, what suggests positive feedbacks to cause thedominance by Myrsine umbellata. We also found a positive relationship between sum of basisand species richness, probably reflecting a fertility gradient. Contrary to our expectations, wefound no relationship between total defenses and total soil fertility or soil variables, whatcould result from low variability in soil fertility at fine scale or of high phenotypic variability.Presence of tannins was positively related to organic matter, possibly reflecting a strategytowards lower tolerance due to low reserve allocation or interactions with other resources.However, since tannins decrease leaf decomposition rates, organic matter could beaccumulating in soil. Overall, we suggest that soil is an important factor structuring cerradocommunity even at fine scales and that the dominance of cerrado species could be related topositive plant-soil feedbacks. / O solo, juntamente com o fogo e as variações climáticas, é considerado um dos principaisdeterminantes do cerrado brasileiro, a savana mais rica do mundo. O solo pode influenciar asespécies de planta selecionando aquelas adaptadas a explorar e competir por recursos, mastambém pode influenciar os padrões de alocações em defesas contra herbivoria. Emboramuitos estudos tenham se voltado a entender as relações entre solo e vegetação no cerrado,poucos se focaram efeitos em escala local. De forma geral, nossa expectativa é de quedescritores da comunidade, como composição florística, riqueza, equabilidade, diversidade eabundância total estejam relacionados com o solo, mesmo em escala local, dentro de umadeterminada fisionomia, e que plantas em solos pobres em nutrientes invistam mais emdefesas contra herbivoria devido ao alto custo em repor as folhas perdidas. Em uma área decerrado, lançamos 100 parcelas contíguas de 25 m2 cada, identificamos todos os indivíduosem nível de espécies, coletamos amostras de solo e medimos os seguintes traços foliares dedefesa contra herbivoria: área foliar específica, razão C:N, quantidade de água, dureza,densidade de tricomas, quantidade de látex, e presença de alcaloides, terpenoides e taninos.Para testar a relação entre a composição florística e as variáveis do solo, usamos uma análisede redundância parcial, controlando a autocorrelação espacial. Para testar a relação entre asvariáveis do solo e (1) a abundância das cinco espécies mais abundantes, (2) a abundânciatotal, (3) a riqueza de espécies, (4) a equabilidade e (5) a diversidade de espécies; para prevera distribuição dos traços de defesa contra herbivoria por meio das variáveis do solo,utilizamos regressões múltiplas ou modelos autorregressivos, na presença de autocorrelaçãoespacial. Encontramos uma baixa relação entre o solo e a composição florística,provavelmente devido à presença de espécies funcionalmente redundantes e espécies comdispersão limitada. O conteúdo de matéria orgânica esteve positivamente relacionado àabundância de Myrsine umbellata, a espécie mais abundante na área, e à abundância total, enegativamente relacionada à equabilidade, o que sugere que um mecanismo deretroalimentação positiva pode ser a causa da dominância de Myrsine umbellata. Tambémencontramos uma relação positiva entre soma de bases e a riqueza de espécies provavelmenterefletindo um gradiente de fertilidade. Contrariamente às nossas expectativas, nãoencontramos relação entre o investimento total em defesas e a fertilidade do solo,provavelmente refletindo uma baixa variação nas variáveis do solo em escala local ouvariações fenotípicas entre indivíduos da mesma espécie ou ambas. Entretanto, a presença detaninos esteve relacionada positivamente com o conteúdo de matéria orgânica, o que poderefletir menor tolerância à herbivoria em solos mais pobres ou uma alta acumulação dematéria orgânica no solo devido à lenta taxa de decomposição de folhas com tanino. De formageral, sugerimos que o solo é um importante fator estruturando a comunidade, mesmo emescala local, e que a dominância de espécies de cerrado pode estar relacionada a mecanismosde retroalimentação positiva.

Made available in DSpace on 2014-12-17T15:55:05Z (GMT). No. of bitstreams: 1 RobertoR_DISSERT.pdf: 1125393 bytes, checksum: 639c9308ec555425dc29f7b3bad222f8 (MD5) Previous issue date: 2014-01-31 / The diversity of fish species from South America has been affected by various anthropogenic practices. Some studies have reported the influence that illegal transferring or introduction of exotic species have on the trophic webs of continental lakes. The loss of diversity on fish populations and consequent impacts on fishery are commonly evidenced in these cases. The Brazilian Northeast has ponds for which exotic Amazonian species were transferred as Extremoz Lake. These environments serve as study models for comparison and investigation about the possible impacts of these introductions. We tested the hypothesis that loss of species that this trend can be related with the insertion of the genus Cichla, commonly documented as top predator in its endemic environment. Possible structural causes that interfere in other processes such as migration were also investigated. Thus, the local ecological knowledge of fishermen and a current ecotrophic model were used. We took samples of phytoplankton, zooplankton and fishes during two annual cycles. Concurrently, we made interviews with the fishing community. In fact, there are relations between the loss of fish and the insertion of peacock bass in Extremoz Lake. However, Cichla kelberi was not indicated as primary factor to explain fish species decline. The construction of bridges located in the Rio Doce was main factor for respondents and what explains loss of species. The migration of saltwater fish and / or from the river to Extremoz Lake is hindered by the unsuitability of the crossing-streams that are under these structures. According to the ecotrophic model Hoplias malabaricus was considered key-species and Cichla kelberi top predator. This last trend was similarly noticed in the stomach and local ecological knowledge of fishermen analysis. Overfishing simulations to Cichla kelberi resulted that only raising its captures in 200%, other native species would increase their biomass values only 15 to 30% (in 6 years).The negative effects of the alien species introduction without prior studies and lack of investments in appropriating these constructions to the needs of the fish fauna structures seem to act simultaneously. Both are causing the decline of fish species richness and consequent local artisanal fishery collapse / A diversidade de esp?cies de peixes da Am?rica do Sul vem sendo afetada por diversas pr?ticas antr?picas. Alguns estudos t?m documentado os efeitos resultantes destas transfer?ncias ilegais de esp?cies ex?ticas. A perda de riqueza da ictiofauna e consequente desarticula??o da pesca t?m sido evidenciadas nestes casos. O nordeste brasileiro apresenta lagoas para as quais foram transferidas esp?cies ex?ticas amaz?nicas, como a Lagoa de Extremoz. Estes ambientes servem como modelos de estudo para fins de compara??o e investiga??o dos poss?veis impactos decorrentes destas introdu??es. Testamos a hip?tese de que a perda de riqueza da ictiofauna e consequente desarticula??o da pesca artesanal exibem rela??o com a inser??o do g?nero Cichla, comumente documentado como predador de topo em seu ambiente end?mico. Poss?veis causas estruturais que interferissem em outros processos, como os de migra??o, tamb?m foram investigadas. Para tanto, o conhecimento ecol?gico local dos pescadores e um modelo ecotr?fico atual foram utilizados. Durante dois ciclos anuais, efetuamos amostragens de fitopl?ncton, zoopl?ncton e peixes. Concomitantemente, efetuamos entrevistas com a comunidade de pescadores. Segundo os resultados obtidos, pode-se inferir que existe um padr?o de queda de riqueza das esp?cies de peixes da lagoa de Extremoz. Por?m, Cichla kelberi n?o foi indicado como fator principal para que este decl?nio viesse a ocorrer. A constru??o de pontes, localizadas no Rio Doce, foi apontada pelo conhecimento ecol?gico local como fator prim?rio para que o n?mero de esp?cies diminu?sse neste ambiente. A migra??o de peixes de ?gua salgada e/ou provenientes do Oceano Atl?ntico para a Lagoa de Extremoz parece ter sido impedida com os impactos causados por estas obras c?veis, especialmente no que diz respeito ? inadequa??o das manilhas ?s necessidades da ictiofauna. Segundo o modelo ecotr?fico, Hoplias malabaricus foi considerada esp?cie-chave e Cichla kelberi predador de topo, tend?ncia similarmente obtida nas an?lises estomacais e atrav?s do conhecimento ecol?gico local dos pescadores. Simula??es de sobre pesca para o tucunar? indicaram inviabilidade em rela??o ao aumento da captura desta esp?cie. Em 6 anos, mesmo aumentando a pesca de tucunar? em 200%, outras esp?cies poderiam aumentar sua biomassa somente em 15 e 30%. A influ?ncia negativa da inser??o de esp?cies ex?ticas sem estudo pr?vio para determinados ambientes e a falta de investimento em estruturas adequadas ?s necessidades da ictiofauna parecem atuar simultaneamente, causando o decl?nio da riqueza de esp?cies e consequente colapso da pesca artesanal local