Nas últimas décadas, em decorrência da globalização e do comércio internacional, o deslocamento de espécies para longe de suas regiões de origem tem crescido em frequência e extensão, aumentando o risco de invasões biológicas, que podem impactar significativamente a economia, o funcionamento dos ecossistemas e causar perdas de biodiversidade. A erradicação de espécies invasoras tem poucas chances de sucesso, de modo que prevenir a invasão constitui a melhor alternativa de manejo. Técnicas de modelagem preditiva de distribuição têm sido globalmente aplicadas para prever a distribuição potencial de espécies invasoras. No Brasil, são poucos e recentes os estudos sobre invasões biológicas. Visando ampliar o conhecimento sobre plantas consideradas invasoras e sua distribuição no estado de São Paulo, neste estudo aplicamos técnicas de modelagem preditiva a 10 espécies. Para cada uma delas buscamos caracterizar o padrão de invasão e identificar os fatores ambientais atuantes que limitam ou potencializam sua distribuição, por meio de modelos multi-hierárquicos de nicho ecológico. Para tanto, coletamos informações de ocorrência dessas espécies em todo o mundo e registramos coordenadas geográficas, características das populações e dos ambientes invadidos por essas espécies em todos os tipos de vegetação e em todas as regiões do estado de São Paulo. Com base nesses dados, caracterizamos o padrão de invasão de cada espécie e a invasibilidade de cada tipo vegetacional estudado. Aplicamos a metodologia de modelagem multi-hierárquica de nicho ecológico por meio do algoritmo MaxEnt em macro escala para todo o globo e em meso escala para o estado de São Paulo. Apesar das peculiaridades das espécies e dos tipos de vegetação, nossos resultados evidenciam a influência do estado de conservação do ecossistema e da posição na paisagem sobre a severidade da invasão e, também, sobre a invasibilidade dos tipos de vegetação em escala local. Mesmo os tipos de vegetação mais resistentes, como a restinga e a floresta ombrófila densa, podem se tornar suscetíveis à invasão em função de distúrbios e da pressão de propágulos. Em fragmentos conservados, porém, são raras as espécies exóticas capazes de se estabelecer e se tornar uma ameaça real à conservação. As fitofisionomias mais abertas do Cerrado mostraram-se como os tipos de vegetação suscetíveis à invasão pelo maior número de espécies, entre as estudadas. Em macro escala, os modelos de nicho ecológico identificaram as áreas potenciais de invasão e revelaram os limites fisiológicos de temperatura e precipitação para cada espécie, enquanto em meso escala, os modelos de nicho refinaram estas previsões e revelaram novos padrões associados com a distribuição das espécies na escala do estado de São Paulo. Este estudo gera contribuições importantes em termos de informação sobre as características e áreas potenciais de invasão para gestores e tomadores de decisão no processo de prevenção e controle de invasões, bem como identifica limites e fatores ambientais que contribuem para a melhor compreensão de invasões biológicas no Brasil. De forma geral, a abordagem multi-hierárquica se mostrou uma ferramenta poderosa para explorar padrões de distribuição em escalas apropriadas com os objetivos de conservação, prevenção e controle de espécies exóticas. / In recent decades, as a result of globalization and international trade, the movement of species away from their native regions has grown in frequency and extent, increasing the risk of biological invasions, which can significantly impact the economy, the functioning of ecosystems and cause biodiversity loss. The eradication of invasive species it is not an easy task, usually with little chance of success, so that prevent the invasion is still the best management alternative. Predictive species distribution modeling techniques have generally been applied to predict the potential distribution of invasive species. In Brazil, studies on biological invasions are recent and insufficient to understand the current invasive status. To enhance understanding about invasive plants and its distribution in the state of São Paulo, in this study we apply predictive modeling techniques to 10 species considered invasive. For each of the selected species we seek to characterize the invasion pattern and identify the active environmental factors that limit or leverage its distribution through multihierarchical ecological niche models. For this purpose, we collect information for these species occurring worldwide and recorded geographical coordinates characteristics of populations and environments invaded by these species in all vegetation types and in all regions of the state of São Paulo. Based on these data, we characterize the invasion pattern of each species and the invasiveness of each vegetation type studied. We applied the multihierarchical ecological niche modeling methodology through MaxEnt algorithm in macro scale for the entire globe and meso scale for the state of São Paulo. Despite the peculiarities of species and vegetation types, our results highlight the influence of ecosystem conservation status and position in the landscape on the severity of the invasion and on the invasiveness of vegetation types on a local scale. Even the most resistant types of vegetation, such as the restinga and the tropical rain forest, can become susceptible to invasion because of disturbances and seedlings pressure. In conserved fragments, however, exotic species were rarely able to settle down and become a real threat to conservation. The more open forms of the Cerrado vegetation types appeared as the most susceptible to invasion by most of the studied species. In macro scale, the ecological niche models identified the potential areas of invasion and revealed the physiological limits of temperature and precipitation for each species, while in meso scale, niche models refined these projections and revealed new patterns associated with the distribution of species on the scale of São Paulo. This study provides important contributions in terms of information about the characteristics and potential areas of invasion for managers and decision makers in prevention and control of invasions and identifies limitations and environmental factors that contribute to a better understanding of biological invasions in Brazil. In general, the multihierarchical approach proved to be a powerful tool to explore patterns of distribution at scales compatible with conservation objectives, prevention and control of alien species.

Made available in DSpace on 2016-06-02T19:31:53Z (GMT). No. of bitstreams: 1 3434_Elementos pre-textuais.pdf: 238495 bytes, checksum: 038e364781dedc63c35cb9deef7e549c (MD5) Previous issue date: 2011-02-01 / Universidade Federal de Sao Carlos / The main objectives of this dissertation were to evaluate the risks of introduction of Euterpe oleracea in the Atlantic Rainforest and its influence over a native population of Euterpe edulis. We investigated the ecological and morphological features of these species also including pre-existing data about hybrids experimentally produced between them (Chapter 1). We did the populations sampling in two areas of Atlantic Rainforest, in southern São Paulo state: Carlos Botelho State Park (CBSP) and Ilha do Cardoso State park (ICSP). At CBSP, we sampled the co-occurring populations of E. edulis and E. oleracea and at ICSP we sampled the control population for E. edulis, which is free from E. oleracea introduction. We evaluated the characteristics of growth in diameter and height of these populations and its ontogenetic stages through the allometric relationships between diameter and height (Chapter 2). We also analyzed population ecology and distribution of these three species (Chapter 3). For the co-occurring populations we evaluated the fruit biometry and observed the frugivorous bird community (Chapter 3). Our results indicated that two Euterpe species may be well represented for the same ontogenetic stages and the three studied populations presented similar allometry. Concerning to population ecology we observed that E. edulis population at CBSP presents total individuals density lower that ICSP population. Both E. edulis populations do not show a significant aggregation. Population of E. oleracea shows a reduced N, high aggregated distribution and is also capable of dispersing itself outside the original range of plantation. We also observed that these species produce morphologically similar fruits but with different sizes, with bigger fruits from E. oleracea and smaller from hybrids. Finally, we detected that E. oleracea shares the same guild of frugivorous birds and may displace dispersers from E. edulis. We concluded that E. oleracea is capable to successfully establish, reproduce and disperse itself and, thus, it is an invasive species in Atlantic Rainforest. Its introduction affects ecological processes linked to pollination, gene fluxes and frugivore and seed dispersion. These changes may be related to genetic mixtures of populations and decreasing of population of E. edulis. Finally, the introduction of E. oleracea may perform one more threat to maintenance of E. edulis populations, which are already threatened by over exploitation. / Os objetivos principais desta dissertação foram avaliar os riscos da introdução de Euterpe oleracea na Floresta Ombrófila Densa Atlântica e sua influência sobre uma população nativa de Euterpe edulis. Para isso, levantamos as características morfológicas e ecológicas destas espécies, incluindo também dados pré-existentes sobre os híbridos produzidos experimentalmente entre elas (Capítulo 1). Realizamos a amostragem das populações em dois locais de Floresta Ombrófila Densa Atlântica, no sul do estado de São Paulo: O Parque Estadual Carlos Botelho (PECB) e o Parque Estadual Ilha do Cardoso (PEIC). No PECB, amostramos as populações co-ocorrentes de E. edulis e E. oleracea e no PEIC amostramos a população controle de E. edulis, que se encontra sem a presença de E. oleracea. Avaliamos as características de crescimento em diâmetro e em altura destas populações e de seus estádios ontogenéticos através das relações alométricas entre diâmetro e altura (Capítulo 2). Analisamos também a ecologia populacional e distribuição espacial das três populações. (Capítulo 3). Para as duas espécies co-ocorrentes avaliamos a biometria de frutos e a observação da comunidade de aves frugívoras (Capítulo 3). Nossos resultados indicaram que as duas espécies de Euterpe podem ser representadas pelos mesmos estádios ontogenéticos e as três populações estudadas apresentam relações alométricas similares. Quanto à ecologia populacional, observamos que a população de E. edulis do PECB apresenta menor densidade total de indivíduos do que a população do PEIC. Ambas não apresentam agregação significativa. A população de E. oleracea apresenta N reduzido, grande agregação e ainda é capaz de se dispersar além da área inicial do plantio. Observamos ainda que as espécies produzem frutos morfologicamente similares, mas com tamanhos maiores em E. oleracea e menores no híbridos. Finalmente, detectamos que E. oleracea compartilha a mesma guilda de aves frugívoras e pode deslocar dispersores de E. edulis. Concluímos que E. oleracea é capaz de se estabelecer, reproduzir e dispersar com sucesso e que, portanto, é uma espécie invasora na Floresta Atlântica. Sua introdução afeta os processos ecológicos locais ligados à polinização, aos fluxos gênicos e à frugivoria e dispersão de sementes. Tais alterações podem estar relacionadas à mistura gênica das populações e à diminuição de visitas das populações de E. edulis. Por fim, a introdução de E. oleracea pode constituir mais uma ameaça à manutenção das populações de E. edulis, que já se encontram ameaçadas pela exploração predatória.

Made available in DSpace on 2015-03-26T13:45:31Z (GMT). No. of bitstreams: 1 texto completo.pdf: 933167 bytes, checksum: ca9e74d4418395492daa526f1c88232c (MD5) Previous issue date: 2010-02-25 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / This work aims to study the Theory of Optimal Control its application to biological problems. We studied two models of optimal control: the first applied to biological invasions in a network of lakes and the second applied to the treatment of cancer through the use of drugs. The models that describe the dynamics of the problems considered are based on ordinary differential equations. The problems are placed in the form of an optimal control problem, where in the first we minimize the cost, which is composed of the added cost of preventing in the damage caused by invasion, and in the second we minimize the density of tumor cancer in end time of treatment and the effects (ills) caused by the drug during the treatment period. / Este trabalho tem como objetivo o estudo da Teoria do Controle Ótimo e sua aplicação a problemas biológicos. Estudamos dois modelos de controle ótimo: o primeiro aplicado a invasões biológicas em uma rede de lagos e o segundo aplicado ao tratamento de câncer através do uso de drogas. Os modelos que descrevem a dinâmica dos problemas considerados são baseados em equações diferenciais ordinárias. Os problemas são colocados no formato de um problema de controle ótimo, onde no primeiro minimizamos o custo, que é composto do custo de prevenção adicionado aos prejuízos causados pela invasão, e no segundo minimizamos a densidade do tumor de câncer no tempo final do tratamento e os efeitos (males) causados pela droga durante o tempo de tratamento.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-09-27T14:45:08Z No. of bitstreams: 1 carolinealmeidadovale.pdf: 810537 bytes, checksum: 3c0b5d13937779867eb8513036f432c2 (MD5) / Approved for entry into archive by Diamantino Mayra (mayra.diamantino@ufjf.edu.br) on 2016-09-27T15:15:44Z (GMT) No. of bitstreams: 1 carolinealmeidadovale.pdf: 810537 bytes, checksum: 3c0b5d13937779867eb8513036f432c2 (MD5) / Made available in DSpace on 2016-09-27T15:15:44Z (GMT). No. of bitstreams: 1 carolinealmeidadovale.pdf: 810537 bytes, checksum: 3c0b5d13937779867eb8513036f432c2 (MD5) Previous issue date: 2016-02-19 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ao longo dos anos humanos tem transportado espécies de forma proposital ou despercebida para fora de sua área natural. Espécies introduzidas podem trazer prejuízos ambientais e econômicos e são a segunda principal causa de perda da biodiversidade, sendo apenas superada pela supressão de ambientes. Os primatas sempre mantiveram uma relação muito estreita com os seres humanos facilitando com que fossem transportados para fora de seus limites naturais. A espécie Callithrix penicillata ocorre tipicamente no cerrado e é relatada como invasora em diversos estados do país, suas populações introduzidas tem se tornando um problema para a conservação devido a seu alto potencial de ocupação, predação de fauna nativa competição com congêneres nativos e hibridização. Para iniciar ações de manejo é preciso conhecer os locais já invadidos e os possíveis de invasão. Neste sentido a modelagem de distribuição potencial (MDP) baseada nos modelos ecológicos de nicho, tem se demonstrado uma maneira rápida, confiável e com baixo custo para identificar áreas com maior probabilidade de ocorrência de uma espécie. Neste estudo utilizamos a modelagem de distribuição potencial (MDP) para identificar áreas com maior probabilidade de ocorrência de uma espécie, através do software Maxent (Máxima Entropia). Este trabalho tem como objetivo principal conhecer o potencial de invasão da espécie Callithrix penicillata no território brasileiro. E como objetivos específicos conhecer a distribuição atual do sagui C. penicillata e confrontar com aquela encontrada na literatura, conhecer as áreas mais suscetíveis à invasão e discutir o problema que a introdução dessa espécie vem causando nas regiões onde é uma espécie invasora. O valor encontrado foi de AUC=0.966 para dados de treino e AUC=0.919 para os dados de teste, com valor da curva bem próximo a 1. Pelo teste Jackknife, observamos que a variável mais correlacionada a distribuição foi a sazonalidade da temperatura (AUC = 0,86), coincidindo com outros estudos que demonstram que variáveis climáticas influenciam a distribuição de primatas. As regiões mais apontadas como susceptíveis a invasão foi a Floresta Atlântica da região Sudeste seguida pelo Sul. A Floresta Atlântica por possuir alto nível de endemismo, e as regiões Sul e Sudeste por terem maior concentração demográfica, contribuem para que a invasão biológica dos saguis se torne um fator preocupante. / Over the years humans have transported species purposeful or unnoticed out of its natural range. Introduced species can bring environmental and economic damages and are the second leading cause of biodiversity loss, being surpassed only by suppressing environments. Primates have always maintained a very close relationship with humans facilitating them to be transported out of their natural limits. The Callithrix penicillata species typically occurs in the cerrado and is reported as invasive in several states of the country, its population has made becoming a problem for conservation because of its high potential for occupation, native wildlife predation and competition with native hybridization counterparts. To initiate management actions we need to know the locals already invaded and possible invasion, thus the potential distribution modeling (MDP) based on ecological models niche, it has proved a fast, reliable and cost to identify areas with greater probability of some sort. In this study we used the potential distribution modeling (MDP) to identify areas with higher probability of occurrence of a species through the Maxent software (Maximum Entropy). This work aims to know the invasion potential of the species in Brazil. And the following objectives know the current distribution of C. penicillata marmoset and confront with that found in the literature, know the areas most susceptible to invasion and discuss the problem that the introduction of this species has caused in the regions where it is an invasive species. The value found was AUC = 0.966 for training data and AUC = 0919 for the test data with the value very close to curve 1. At Jackknife test, we found that the most correlated variable distribution was seasonality temperature (AUC = 0, 86), coinciding with other studies showing that environmental factors influence the distribution of primates. The most frequently mentioned site susceptible to invasion was the Atlantic Forest of the Southeast region followed by the South. The Atlantic Forest for having high levels of endemism, and the South and Southeast regions to have higher population concentration, contribute to the biological invasion of marmosets are become a concern.

Orientador: Louis Bernard Klaczko / Tese (doutorado) - Universidade Estadual de Campinas, Insituto de Biologia / Made available in DSpace on 2018-08-04T02:57:08Z (GMT). No. of bitstreams: 1 Araripe_LucianaOrdunha_D.pdf: 1442005 bytes, checksum: 69889cecab16cb4c8feae92d4eb04c7e (MD5) Previous issue date: 2005 / Resumo: A espécie Zaprionus indianus expandiu sua distribuição geográfica recentemente, a partir da invasão do continente sul-americano. O primeiro registro data de apenas seis anos, e acredita-se que a origem seja sul-africana. Hoje, indivíduos dessa espécie são encontrados numa amplitude latitudinal de 35o, do Uruguai a Belém (Brasil). A chegada de Z. indianus no Brasil apresenta uma oportunidade rara de se estudar um evento de invasão desde seu início. O estudo de características fisiológicas, morfológicas e genéticas de populações brasileiras pode ajudar a construir hipóteses para o sucesso de Z. indianus nas etapas de invasão, além de indicar o potencial para evolução e diferenciação fenotípica. Um aspecto fisiológico estudado nesta tese foi a condição reprodutiva em machos que foram submetidos a extremos de temperatura ao longo de seu desenvolvimento. O estresse térmico causa esterilidade nos machos e a investigação dos limites (superior e inferior) da curva de fertilidade relativa à temperatura, complementa os dados de viabilidade na caracterização do potencial de ocupação de áreas novas por espécies cosmopolitas. Quanto à morfologia, um aspecto estudado foi o dimorfismo sexual no número de cerdas abdominais em uma população africana. Dimorfismo sexual para este caráter foi observado em várias espécies em estudos anteriores, embora padrões diferentes tenham sido encontrados. Nesta tese o padrão observado em Z. indianus foi comparado com o de outra espécie cosmopolita, Drosophila melanogaster. Um terceiro ponto abordado nesta tese foi a investigação de 10 populações brasileiras quanto à variação fenotípica (tamanho e forma da asa). Além das diferenças entre populações, uma abordagem interessante é o quanto de variação está presente dentro de cada população. Ainda, é importante saber o quanto dessa variação é herdável para estimarmos qual a capacidade evolutiva da população. O estudo revelou a ocorrência de alta variabilidade fenotípica dentro e entre populações, além de variação genética aditiva suficiente para promover a evolução de caracteres relacionados à forma da asa / Abstract: The species Zaprionus indianus has recently expanded its geographical distribution with the invasion of the South American continent. The first record dates of only six years, and the origin is probably the South Africa. Nowadays, individuals of this species can be found in a latitudinal range of 35o, from Uruguai to Belém (Brazil). The arrival of Z. indianus in Brazil presents a rare opportunity of studying an event of invasion from its beginning. The study of physiological, morphological and genetic traits in Brazilian populations may contribute to generate hypothesis for the success of Z. indianus in the stages of invasion. Also, it may indicate the potential for evolution and phenotypic differentiation. One physiological trait studied in the current thesis was the relationship of fertility and the temperature of development. Extreme temperatures cause sterility in males and the study of the limits (upper and lower) of the fertility curve complements the data on viability for the characterization of the potential of cosmopolitan species to occupy new areas. One morphological character studied was the sexual dimorphism for the number of abdominal bristles in one African population. A significant sexual dimorphism for this trait was observed in several species in previous studies, though different patterns have been found. In the current work the pattern observed in Z. indianus was compared to the pattern for another cosmopolitan species, Drosophila melanogaster. The third approach of this thesis was the study of the phenotypic variation (size and shape of the wing) present in 10 Brazilian populations. Besides the differences among populations, an interesting approach is the amount of variation present within each population. Also, it is important to know the proportion of this variation that is heritable, which allows an estimate of the evolutionary potential of the population. This study revealed the occurrence of high phenotypic variability within and between populations. In addition, enough additive genetic variation exists to promote the evolution of traits related to the shape of the wing / Doutorado / Genetica Animal e Evolução / Doutor em Genetica e Biologia Molecular

Feral swine (Sus scrofa) are an invasive species in the Mississippi Alluvial Valley (MAV). They cause millions in damage annually to agriculture, and likely negatively affect native wildlife species. Using camera traps, I monitored 36 forest patches within the MAV to assess the effects of swine invasions on native wildlife species richness. I also modified the double-observer point count technique into a new method for estimating swine abundance with camera traps. Feral swine suppressed native vertebrate richness by 26% when compared to uninvaded patches. I validated the new double-observer technique by determining if it could detect an abundance-area relationship in wildlife populations and estimate a known decrease in abundance following swine removal. This technique was sensitive enough to detect the increase and decrease in abundance and estimated the number of individuals removed from the population relatively accurately. This technique may be useful in the future to manage feral swine populations.

An intensive sampling of all ant species encountered on 6 Hawaiian Islands: Big Island, Maui, Oahu, Kauai, Molokai, and Lanai took place between 1988 and 1996. Species presence and absence was recorded at each site. Using remote sensing, variables were added insitu and used throughout my analysis. Species accumulation curves suggest that sampling was comprehensive. There is a significant trend between island area and species richness which validates the Theory of Island Biogeography for invasive species. Islands were found to be significantly nested by area, order, and tourism. Cluster analysis shows a link between elevation, land-use and island, and species presence. Predictive models can be built to predict spread of particular ant species as they continue toward equilibrium.

No description available.

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH SUMMARY: Climate change and biological invasions are major components of global change induced by human activity and are considered major drivers of global biodiversity decline in terrestrial ecosystems. These drivers interact synergistically and render ecosystems vulnerable to invasion by invasive alien species. Grasses are a group of invasive plants that easily respond to global changes and alter native plant community structure and ecosystem processes, such as fire frequency. To date there have been few studies that assess the ecological drivers and effects of invasive grass species on arid and semi-arid ecosystems of South Africa. Fountain grass (Pennisetum setaceum) is a widely distributed invasive alien perennial grass from North Africa and the Middle East, valued by horticulturalists worldwide. It spreads along the edges of roads on the outskirts of most towns, and is common on mine spoil in many areas throughout South Africa. Occasionally, it escapes into natural vegetation along drainage lines or after fires. This grass can be a costly problem for agriculture and biodiversity conservation as it is unpalatable and increases fire risk. Understanding its distribution and invasive dynamics will contribute to better management and control practices. The main objective of this study was to understand the ecology and invasion processes of P. setaceum across South African environmental gradients, and use it as a model to understand the synergistic relationships between biological invasions and other global change (climate and land use) scenarios. This study provides the first assessment of how P. setaceum overcomes different invasion barriers in South Africa as an emerging invader, in comparison with other parts of the world where it has already become problematic. A number of management and control options for this grass and other similar perennial grasses result from this study. Specifically, the study provides comprehensive understanding of: 1) the distribution and habitat preferences of P. setaceum in arid and semi-arid parts of South Africa, 2) environmental resources and habitat conditions that promote its invasive potential, 3) growth and reproductive performance across environmental gradients, 5) the response of an arid ecosystem to P. setaceum invasion and fire promotion, and 6) the predicted future distribution of this grass in South Africa under scenarios of climate change and spread. The study has found that road-river interchanges are ideal sites for P. setaceum growth and that these sites should be targeted for management and control of this species. P. setaceum was found to persist under diverse biome environments, which is attributed to local adaptation. Disturbance was found to be a major factor promoting fountain grass invasion into semi-natural areas away from roadsides. Major clean-ups of this grass should focus on disturbed areas, especially in the fertile parts of the fynbos region where the grass has high climatic suitability. Management and control should also focus on areas with high nutrients and extra water, as these areas facilitate growth and reproduction. The dynamics of P. setaceum invasion and spread makes it a good model for management of similar emerging invasive perennial grasses in similar ecosystems. / AFRIKAANSE OPSOMMING: Klimaatsverandering en biologiese indringing is grootskaalse komponente van mensgedrewe globale veranderinge, en kan ook gesien word as prominente drywers van die huidige afname in globale biodiversiteit van terrestriële ekosisteme. Hierdie drywers werk saam in sinergie, en laat sodoende ekosisteme kwesbaar vir indringing deur uitheemse indringerplante. Grasse is ‘n groep indringerplante wat maklik reageer ten opsigte van globale veranderinge en verander inheemse plantgemeenskapstruktuur en ekosisteem prosesse, soos byvoorbeeld veldbrand frekwensie. Tot op hede is daar wynig studies gedoen wat die ekologiese drywers en effekte van indringergras spesies in droë en semi-droë ekosisteme van Suid-Afrika assesseer. Pronkgras (Pennisetum setaceum) is ‘n wyd verspreide meerjarige uitheemse indringergras, oorspronklik vanaf Noord-Afrika en die Midde-Ooste, en word waardeer deur tuinboukundiges wêreldwyd. Dit versprei al langs padrande aan die buitewyke van meeste dorpe, en is algemeen op ou mynhope in verskeie dele van Suid-Afrika. Somtyds ontsnap hierdie gras langs dreineringskanale of na veldbrande, en beland so in die omringende natuurlike plantegroei. Hierdie gras kan ‘n duur probleem word vir landbou asook biodiversiteit bewaring omdat dit onsmaaklik is vir diere, en dit verhoog veldbrand risiko. ‘n Beter begrip van pronkgras verspreiding en indringingdinamika sal bydra tot verbeterde bestuur en kontrole praktyke. Die hoofdoel van hierdie studie was om die ekologie en indringing prosesse van P. setaceum regoor Suid-Afrikaanse omgewingsgradiente te begryp, en dit dan te gebruik as ‘n model om die sinergistiese verhoudings tussen biologiese indringing en ander globale veranderinge (klimaat en grondgebruik) te verstaan. Die studie verskaf die eerste assessering van hoe P. setaceum verskillende indringing hindernisse in Suid-Afrika oormeester as ‘n opkomende indringer, in vergelyking met ander dele van die wêreld waar dit al klaar problematies is. Hierdie studie verskaf uiteindelik ‘n aantal bestuur en kontrole opsies vir hierdie en ander soortgelyke meerjarige grasse. Die studie verskaf spesifiek ‘n deeglike verstaan van: 1) die verspreiding en habitat voorkeure van P. setaceum in droë en semi-droë areas in Suid-Afrika, 2) omgewingshulpbronne en habitat toestande wat hierdie plant se indringing potensiaal verhoog, 3) groei- en voortplantingsvertoning oor verskillende omgewingsgradiente, 4) die reaksie wat ‘n droë ekosisteem toon teenoor P. setaceum indringing en veldbrand verhoging, en 5) die toekomstige verspreiding van hierdie gras in Suid-Afrika onder voorspellings van klimaatsverandering en verspreiding. Die studie het gevind dat pad-rivier tussengange ideale liggings is vir P. setaceum vestiging, en dat hierdie liggings dus geteiken moet word vir bestuur en kontrole doeleindes. P. setaceum toon volharding onder diverse bioom omgewings, wat toegeskryf word aan plaaslike aanpassing. Daar is gevind dat versteuring ‘n groot faktor is in die verhoging van pronkgras indringing in semi-natuurlike areas weg van padskouers. Grootskaalse pronkgras uitroeiing projekte moet fokus op versteurde gebiede, veral in die vrugbare dele van die fynbos streek, waar hierdie gras hoë klimaatsgeskiktheid toon. Bestuur en kontrole programme moet ook fokus op areas met hoë nutriente inhoud en ekstra water, aangesien hierdie areas groei en voortplanting vergemaklik. Die dinamika van P. setaceum indringing en verspreiding maak dit ‘n goeie model vir die bestuur van soortgelyke opkomende meerjarige indringergrasse in soortgelyke ekosisteme.

<p>Biological invasions are an important issue of global change and an increased understanding of invasion processes is of crucial importance for both conservation managers and international trade. In this thesis, I have studied the invasion of the brown seaweed <i>Fucus evanescens</i>, to investigate the fate and effect of a perennial, habitat-forming seaweed introduced to a coastal ecosystem. A long-term study of the spread of <i>F. evanescens</i> in Öresund (southern Sweden) showed that the species was able to expand its range quickly during the first 20 years after the introduction, but that the expansion has been slow during the subsequent 30 years. Both in Öresund and in Skagerrak, the species is largely restricted to sites where native fucoids are scarce. Laboratory experiments showed that the restricted spread of <i>F. evanescens</i> cannot be explained by the investigated abiotic factors (wave exposure and salinity), although salinity restricts the species from spreading into the Baltic Sea. Neither did I find evidence for that herbivores or epibiota provide biotic resistance to the invader. On the contrary, <i>F. evanescens</i> was less consumed by native herbivores, both compared to the native fucoids and to <i>F. evanescens</i> populations in its native range, and little overgrown by epiphytes. Instead, the restricted spread may be due to competition from native seaweeds, probably by pre-occupation of space, and the establishment has probably been facilitated by disturbance. </p><p>The studies provided little support for a general enemy release in introduced seaweeds. The low herbivore consumption of <i>F. evanescens</i> in Sweden could not be explained by release from specialist herbivores. Instead, high levels of chemical anti-herbivore defence metabolites (phlorotannins) could explain the pattern of herbivore preference for different fucoids. Likewise, the low epibiotic colonisation of <i>F. evanescens </i>plants could be explained by high resistance to epibiotic survival. This shows that colonisation of invading seaweeds by native herbivores and epibionts depends on properties of the invading species. The large differences between fucoid species in their quality as food and habitat for epibionts and herbivores imply that invasions of such habitat-forming species may have a considerable effect on a number of other species in shallow coastal areas. However, since <i>F. evanescens</i> did not exclude other fucoids in its new range, its effect on the recipient biota is probably small.</p>