Biotic interactions are known to shape natural community assemblages and biodiversity. Positive interactions such as facilitation have recently received attention in ecological food webs. Mechanistic models have improved our understanding of these complex food web interactions. Here, focus is given to a three-species food web system with a beach dune natural community in mind. In the last decade, there has been a series of studies investigating intraguild predation between two major loggerhead sea turtle nest predators, North American raccoons and Atlantic ghost crabs. Studies have also highlighted that ghost crab predation assists raccoons in finding nests (i.e., facilitated predation). However, the combined effects of these two intraguild interactions and their consequences on nests have not been examined explicitly. The aims of this study were to (i) develop a three-species, ordinary differential equation model (ii) implement a sensitivity analysis to understand the influence of facilitation and other factors in driving species richness and abundance and (iii) characterize the dynamic interactions between intraguild predators and their effects on a shared resource. Interactions between ghost crabs and sea turtle eggs and facilitation can yield a wide variety of species abundance responses and were influential factors in the model. I found that high secondary sea turtle egg depredation and low facilitated predation by raccoons led to three species co-existence regions in the model. Controlling for nest predators at higher abundance levels showed that ghost crabs had a larger negative effect on sea turtle egg abundance responses when compared to raccoons. This suggests that interactions between sea turtle eggs and ghost crabs appear to be important and potential sea turtle nest management implications are discussed such as the use of ghost crab exclusion devices.

One of the basic questions of concern in mathematical biology is the long-term survival of each species in a set of populations. This question is particularly puzzling for a natural system with omnivory due to the fact that simple mathematical models of omnivory are prone to species extinction. Omnivory is defined as the consumption of resources from more than one trophic level. In this work, we investigate three omnivory models of increasing complexity. We use the notion of permanent coexistence, or permanence, to study the long-term survival of three interacting species governed by a mixture of competition and predation. We show the permanence of our models under certain parameter restrictions and include the biological interpretations of these parameter restrictions. Sensitivity analysis is used to obtain important information about meaningful parameter data collection. Examples are also given that demonstrate the ubiquity of omnivory in natural systems. / Ph. D.

Native to Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an invasive non-native ladybird in Europe and North America, where it was widely introduced as a biological control agent of aphids and coccids. There were three main objectives of this study: firstly, to investigate the spread and distribution of H. axyridis in Europe from the start of the invasion process; secondly, to study its ecology in Great Britain; and thirdly, to examine its effects on native ladybirds in Britain. In Europe, collaborations with a network of scientists allowed the collation of H. axyridis occurrence data from across the continent. In Great Britain, a web-based public survey (www.harlequin-survey.org) was used, leading to the receipt of over 10,000 verified records of H. axyridis between 2004 and 2008. National land cover data enabled the habitats used by H. axyridis to be identified across Great Britain. These datasets were analysed in order to study the spread and ecology of H. axyridis in Europe and Britain. Fieldwork over a three year period (2006 to 2008) was carried out to examine changes in ladybird species assemblages during the invasion phase of H. axyridis in eastern England. Laboratory work was conducted to detect intraguild predation by H. axyridis, through PCR analyses of gut contents of field-collected ladybirds. In Europe, H. axyridis has spread since 2001 at the rate of approximately 200km yr-1. It has become established in at least 23 European countries. The established range extends from Norway in the north to southern France in the south, and from Ukraine in the east to Great Britain in the west. In the first five years of establishment H. axyridis spread north through Britain at the rate of 105km yr-1 and west at the rate of 145km yr-1. Evidence of the production of two generations per year was found, giving H. axyridis an advantage over most native ladybirds in Britain. Although H. axyridis was very common in urban habitats, it increasingly used semi-natural habitats. In addition, whilst the species was most common on deciduous trees, it was increasingly found on herbaceous plants. Aceraceae, Rosaceae and Malvaceae were the dominant plant families used by H. axyridis, especially for breeding. In eastern England H. axyridis increased from 0.1% to 40% of total ladybirds in three years, whilst native aphidophagous ladybirds declined from 84% to 41% of total ladybirds in the same period. Three species in particular experienced declines: Adalia 2-punctata, Coccinella 7-punctata and Propylea 14-punctata. Harmonia axyridis was the most abundant species by the end of the study. Detection of intraguild predation by one coccinellid on another, in the field in Europe, was shown for the first time using PCR techniques: A. 2-punctata DNA was detected in the gut of one of 112 field-collected H. axyridis. Harmonia axyridis has spread very quickly since 2001 and has become one of the most widely distributed coccinellids in Europe. Populations of native aphidophagous ladybirds were negatively affected by the arrival of H. axyridis, partly through intraguild predation.

Loss of biodiversity is a growing problem and hence conservation of species is becoming increasingly important. In this dissertation conservation issues related to the critically endangered European mink (Mustela lutreola) are examined in situ (in the wild) and ex situ (in captivity) on both an individual and community level. It also contains fundamental research as conservation contexts often allow for conclusions beyond applied biology. Individual behavioural differences, e.g. personality, can impact fitness and are hence relevant for conservation. Paper I thus experimentally explores the structure, expression and plasticity of personality in captive European minks. Thereafter paper II investigates if personality affects survival of reintroduced captive-bred animals and if spatiotemporal conditions affects the relationship between personality and survival. Paper III experimentally explores individual dietary specialism and learning in relation to novel prey as this could also impact survival. One of the main threats to the European mink is displacement by the invasive American mink (Neovison vison) wherefore management of American mink is important for European mink conservation. Paper IV hence analyses survey data to study whether native otters and red foxes can suppress American mink populations in north-eastern Europe. In the results three personality trait domains were identified in the European mink: boldness, exploration and sociability. The domains were repeatable but plastic between the non-breeding and breeding season. Reintroduced personality-tested animals survived longer if they were bolder but the effect of exploration was either positive or negative depending on spatiotemporal conditions. This is not only interesting for conservation but provides new insights on how individual behavioural differences could be maintained over evolutionary time. Whilst exploration is likely to be maintained by fluctuating selection pressures, the mechanism seem to vary with domain. The feeding experiments revealed diet choices similar to those found in wild individuals as there were both generalists and different types of specialists. Still, individuals differed in learning time towards novel but natural prey, suggesting that reintroduced animals might differ in their ability to find food after release. This could affect survival also and be related to personality. Survey data revealed that American mink abundances were suppressed by those of red foxes. Previous studies show that foxes are suppressed by lynx, and the abundance pattern of mink in relation to red fox found here indicate the existence of a predator cascade as mink were most abundant where lynx were abundant and vice versa. In several regions in the study area population dynamics indicated either exploitation or interference competition as probable mechanisms whereby foxes suppress minks. However, in many regions there were no relationships between dynamics. This could be due to that exploitation and interference competition might occur simultaneously and thus cancel each other out in the dynamics. Overall this thesis shows the importance of considering individual traits in conservation efforts, and also provides knowledge on the structure, plasticity and evolution of personality. As American mink was suppressed by foxes, management efforts might be most beneficial for species impacted by the mink if they to a larger extent are undertaken in areas with low fox abundances. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.</p>

In this thesis I have investigated the effects of invading top and intermediate consumers in a size-structured fish community, using a combination of field studies, a lake invasion experiment and smaller scale pond and aquaria experiments. The lake invasion experiment was based on introductions of an intermediate consumer, ninespine stickleback (Pungitius pungitius L.), in to allopatric populations of an omnivorous top predator, Arctic char (Salvelinus alpinus L.). The invasion experiment was performed in two tundra lakes and in two birch forest lakes to investigate the effect of climate on the invasion success. I found that the effect of sticklebacks on char was size dependent. Small char suffered reduced growth from resource competition with sticklebacks whereas the maximum size of adult char increased from the addition of a larger prey resource, stickleback. The negative effect of sticklebacks on the growth of small char suggests that sticklebacks may be a better resource competitor than char, which was also supported by the pond and aquaria experiments. The pond experiments also suggested that char were more efficient cannibals than interspecific predators on sticklebacks. Cannibalism in char may limit the recruitment of char and decrease both their predatory and competitive effect on coexisting species and thereby also promote the coexistence of char and sticklebacks. The successful invasion by sticklebacks and their subsequent increases in density suggest that the absence of sticklebacks in char lakes in this region is not caused by biotic interactions with char. Instead, it may be suggested that co-occurrence of sticklebacks and char in the region is limited by dispersal. The char – stickleback system resembles an intraguild predation system with char as the top consumer and stickleback as the intermediate consumer. The effects of the stickleback invasion is also contrasted with a field study of a northern pike (Esox lucius L.) invasion into a system with coexisting char and stickleback, where pike can be viewed as the top consumer and char as the intermediate consumer both feeding on sticklebacks. In this case pike excluded char. The identity of the invading species and the relative strength of the predatory and competitive interactions in the two contrasting systems are discussed in relation to coexistence in intraguild predation systems. I found that the identity of the invading species is of crucial importance for the response at the ecosystem level, and that the inherent size dependency of competitive and predatory interactions in fish communities is important for attaining a mechanistical understanding of the effects of invasive species in lake ecosystems.

Made available in DSpace on 2014-06-11T19:32:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-07-28Bitstream added on 2014-06-13T20:42:37Z : No. of bitstreams: 1 carneiro_tr_dr_jabo.pdf: 521295 bytes, checksum: 441bb6736d540b0f742ff0c1e712a1ae (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho objetivou avaliar a dinâmica populacional de S. frugiperda em ambientes de com alta e baixa diversidade vegetal no entorno da cultura do milho. Além disso, visou-se observar o comportamento e o processo de interação entre os inimigos naturais T. remus, T. pretiosum e D. luteipes. Em nenhuma das datas de avaliação estudadas detectou-se diferença significativa no número médio de adultos e posturas de S. frugiperda. Quanto ao número de lagartas/planta, as áreas de vegetação não diversificada apresentaram maiores valores. Os predadores apareceram em maior número geralmente após os 30 DAE e preferiram as áreas de vegetação não diversificada. Já os parasitóides concentraram-se na cultura até os 25 DAE e preferiram as áreas de vegetação diversificada. Quando foi avaliada a competição entre T. remus e T. pretiosum não constatou-se multiparasitismo. Entretanto, quando as fêmeas de T. remus e T. pretiosum foram colocadas juntas sobre a mesma postura, T. remus predominou. Já quando T. remus foi colocado com D. luteipes observou-se que quando as posturas de S. frugiperda foram expostas primariamente ao parasitóide, D. luteipes as consumiu, mas somente até o terceiro dia após o parasitismo. T. remus parasitou ovos de D. luteipes com até 48h de desenvolvimento embrionário, mas apenas quando as fêmeas do predador estavam ausentes. / This work aimed at evaluating the population dynamics of S. frugiperda in maize culture with high and low vegetal diversity around. And objectified to observe the behavior and interaction between the natural enemies T. remus, T. pretiosum and D. luteipes. Was not detect significant difference in number of S. frugiperda adults and egg masses throughout the time and at the areas of diversified vegetation or not. No diversified areas presented a higher number of larvae/plant. The predators had appeared in higher number after 30 days plants emergence and generally they preferred the areas of no diversified vegetation. The parasitoids were concentrated in the culture until the 25 days after plants emergence and had preferred the areas of diversified vegetation. When S. frugiperda eggs were exposed to either parasitoid previously, there was no emergence of the other parasitoid. And, when the T. remus and T. pretiosum females were placed together with S. frugiperda eggs, it was observed a greater parasitism by T. remus. The results showed a lack of multiparasitism by both species. When S. frugiperda eggs were exposed to T. remus previously, D. luteipes eat the eggs until three days after parasitism. T. remus parasitized D. luteipes eggs until 48h they were laid, but only when predator females were absent.

Made available in DSpace on 2014-06-11T19:32:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-01Bitstream added on 2014-06-13T18:42:57Z : No. of bitstreams: 1 correa_lrb_dr_jabo.pdf: 1543048 bytes, checksum: a8f8dbb9edf2e1247f77433aae591f2e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Objetivou-se avaliar aspectos biológicos de Aphis gossypii em três cultivares de algodoeiro colorido, estudar a biologia e a interação dos predadores Harmonia axyridis e Eriopis connexa alimentados com o pulgão A. gossypii criado nas cultivares, avaliar a densidade de tricomas e glândulas de gossipol das folhas das cultivares e elaborar tabelas de vida de A. gossypii, H. axyridis e E. connexa. As cultivares de algodoeiro colorido utilizadas foram: BRS Rubi, BRS Safira e BRS Verde (Gossypium hirsutum L.r. latifolium Hutch., herbáceo). Os ensaios foram conduzidos em câmara climatizada regulada a 25 ± 2ºC, UR de 70 ± 10% e fotofase de 12 horas. Os substratos alimentares avaliados afetaram a fase ninfal de A. gossypii, sendo que na cultivar BRS Verde verificou-se o menor tempo de duração e na BRS Safira ocorreu o oposto. Em BRS Verde, cultivar com menor densidade de tricomas, observou-se elevada produção de ninfas e a maior taxa líquida de reprodução (R0) por A. gossypii. Os coccinelídeos E. connexa e H. axyridis apresentaram maior número de ovos com elevada viabilidade quando alimentados com pulgões oriundos de BRS Safira, cultivar com baixa densidade de glândulas de gossipol nas folhas. A maior taxa de canibalismo entre as larvas de E. connexa e H. axyridis foi obtida em BRS Verde. Não foi observada predação das larvas de H. axyridis por E. connexa em nenhum dos tratamentos. Portanto, a cultivar BRS Verde favorece os maiores padrões de fecundidade de A. gossypii. BRS Safira proporciona elevada fecundidade de E. connexa e H. axyridis. O coccinelídeo H. axyridis prevalece como predador intraguilda na relação com E. connexa / The aim was to evaluate biological aspects of Aphis gossypii in three colored cotton cultivars, to study the biology and interaction of the predator Harmonia axyridis and Eriopis connexa fed with the aphid A. gossypii reared on the cultivars, evaluate the density of trichomes and gossypol glands in leaves of cultivars and prepare life tables of A. gossypii, H. axyridis and E. connexa. The following colored cotton cultivars were used: BRS Rubi, BRS Safira and BRS Verde (Gossypium hirsutum latifolium Hutch Lr., herbaceous). The tests were conducted in climatized chamber at 25±2 ºC, RH 70± 10% and photophase of 12 hours. The feed substrates evaluated affected the nymphal stage of A. gossypii, and in BRS Verde observed the lowest duration and BRS Safira was the opposite. In BRS Verde with lowest density of trichomes observed high production of nymphs and the highest net reproductive rate (R0) by A. gossypii. The coccinellids E. connexa and H. axyridis had higher numbers of eggs with high viability when fed with aphids from BRS Safira, gossypol glands low density cultivar. The highest rate of cannibalism among larvae of E. connexa and H. axyridis was observed in BRS Verde. It was not observed predation on larvae of H. axyridis by E. connexa in all treatments. Therefore, BRS Safira cultivar supports the hightest fertility patterns of A. gossypii. The BRS Safira provides the high fecundity of E. connexa and H. axyridis. The coccinellid H. axyridis acts as intraguild predator in relation with E. connexa

Made available in DSpace on 2014-06-11T19:35:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-03-28Bitstream added on 2014-06-13T18:47:07Z : No. of bitstreams: 1 rosa_gs_dr_botib.pdf: 493749 bytes, checksum: 45c2a73f301612f6e110bda2833a3842 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este estudo foi caracterizado pela combinação entre experimentação laboratorial e aplicação da teoria populacional. O trabalho foi subdividido em três partes intituladas: Análise de sobrevivência, estrutura de estágios e canibalismo em populações experimentais de Chrysomya albiceps; Curvas de sobrevivência e predação larval entre estágios de vida de Chrysomya albiceps e Modelo de interação intraguilda para predação larval: uma proposição teórica inicial para moscas-varejeiras. Os resultados foram estatisticamente avaliados principalmente com a aplicação de análise de sobrevivência e modelos matemáticos de estrutura de estágios de vida, crescimento populacional dependente da densidade e com formulações fundamentadas em modelos predador-presa. As análises exploraram principalmente a caracterização de padrões estatísticos e matemáticos sob a perspectiva da dinâmica populacional intra e interespecífica. O resultados foram discutidos à luz das teorias populacionais empregadas, dos dados empíricos obtidos e do conteúdo teórico-empírico existente dentro e fora do grupo taxonômico estudado. / One important attribute for individuals of a species is the existence of age classes and life stages. Within each age class, the individuals of a species behave differently, have different types of dependence on the environment and different resource needs. Population dynamics has more frequently been studied in insects with simple mathematical models, which include no stage structure. They provide essential information in terms of temporal and/or spatial dynamics. However, there are several examples of insect species, which exhibit important interactive processes in specific life-stages. The objective of the present study was investigate the population dynamics of C. albiceps employing a combination of mathematical models, survival analysis and laboratory experiments, focusing on survival among life stages and its structure. The study also considered the influence of density-dependence and cannibalism during immature stages on the population dynamics of C. albiceps. The implications of the patterns of dynamic behavior obtained as well as the influences received from cannibalism and density dependence were discussed.

Made available in DSpace on 2014-06-11T19:22:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2009Bitstream added on 2014-06-13T19:49:19Z : No. of bitstreams: 1 galindo_la_dr_botib.pdf: 1002192 bytes, checksum: efafdb9e0e1cd36e8c2d273acc8df569 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / As interações interespecíficas em dípteros califorídeos de importância forense resultam de processos biológicos complexos, envolvendo comportamentos específicos capazes de influenciar tanto a abundância como a diversidade de insetos presentes nos substratos orgânicos em decomposição. Nesse sentido, a presença de determinadas espécies com forte ação interativa, como por exemplo, predadores, competidores ou parasitóides, pode interferir substancialmente na composição da fauna decompositora de cadáveres, com sérias implicações para a estimativa de intervalo pós-morte em investigações criminais. Em estudo prévio foi investigado em laboratório o comportamento de oviposição em L. eximia, C. megacephala e C. albiceps na tentativa de esclarecer se a postura de ovos em moscas-varejeiras ocorre meramente ao acaso, ou se a presença prévia de diferentes espécies pode influenciar a desova por parte das espécies que chegaram ao local subsequentemente. Os resultados encontrados indicam que as espécies L. eximia e C. megacephala escolhem sítios de oviposição em que não há a presença prévia de larvas de C. albiceps, uma espécie predadora intraguilda. Esses resultados sugerem estudos mais aprofundados, preferencialmente em populações naturais, focalizando sobre a interação entre larvas e adultos de moscas-varejeiras, já que há evidências de que fêmeas adultas são capazes de detectar a presença de larvas predadoras, o que influi na decisão oviposicional. Este estudo teve o objetivo geral de investigar a abundância, diversidade e dinâmica comportamental em populações de moscas-varejeiras no contexto de recursos alimentares efêmeros e limitados, considerando a ação da predação intraguilda. A proposta do estudo é criar duas frentes de investigação no contexto de ecologia comportamental, experimentação em campo e modelagem matemática populacional / The interspecific interactions in calliphorid flies of forensic impoltance result of complex biological processes, involving specific behaviors capable of influencing both the abundance and the diversity of insects in organic substrates in decomposition. The presence of certain species with a strong interactive action, such as predators, competitors or parasitoids, can interfere substantially in the composition of the decomposer fauna of corpses, with serious implications for the postmortem interval estimate in criminal inquiries. In a previous study the oviposition behavior in L. eximia, C. megacephala and C. albiceps was investigated in laboratory in the attempt to clarify if the egg laying in blowflies occurs at random, or if the previous presence of different species may influence the oviposition of the species that had arrived subsequently at the substrate. The results suggest that the species L. eximia and C megacephala prefer oviposition substrates, without the previous presence of C. albiceps larvae, an intraguild predator species. These results suggest further studies, preferably in natural populations, focusing on the interaction between larvae and adult of blowflies, since there is evidence that females are able to detect the presence of predator. This study had the general objective of investigating the abundance, diversity and behavioral dynamic in populations of blowflies in the context of limited and ephemeral food resources, considering the effect of intraguild predation. The proposal of the study is to create two fronts of investigation in the context of behavioral ecology, experimentation in field and population mathematical modeling

Orientador: Francisco Jorge Cividanes / Banca: Brigida de Souza / Banca: Valter Arthur / Banca: Nilza Maria Martinelli / Banca: Ricardo Antonio Polanczyk / Resumo: Objetivou-se avaliar aspectos biológicos de Aphis gossypii em três cultivares de algodoeiro colorido, estudar a biologia e a interação dos predadores Harmonia axyridis e Eriopis connexa alimentados com o pulgão A. gossypii criado nas cultivares, avaliar a densidade de tricomas e glândulas de gossipol das folhas das cultivares e elaborar tabelas de vida de A. gossypii, H. axyridis e E. connexa. As cultivares de algodoeiro colorido utilizadas foram: BRS Rubi, BRS Safira e BRS Verde (Gossypium hirsutum L.r. latifolium Hutch., herbáceo). Os ensaios foram conduzidos em câmara climatizada regulada a 25 ± 2ºC, UR de 70 ± 10% e fotofase de 12 horas. Os substratos alimentares avaliados afetaram a fase ninfal de A. gossypii, sendo que na cultivar BRS Verde verificou-se o menor tempo de duração e na BRS Safira ocorreu o oposto. Em BRS Verde, cultivar com menor densidade de tricomas, observou-se elevada produção de ninfas e a maior taxa líquida de reprodução (R0) por A. gossypii. Os coccinelídeos E. connexa e H. axyridis apresentaram maior número de ovos com elevada viabilidade quando alimentados com pulgões oriundos de BRS Safira, cultivar com baixa densidade de glândulas de gossipol nas folhas. A maior taxa de canibalismo entre as larvas de E. connexa e H. axyridis foi obtida em BRS Verde. Não foi observada predação das larvas de H. axyridis por E. connexa em nenhum dos tratamentos. Portanto, a cultivar BRS Verde favorece os maiores padrões de fecundidade de A. gossypii. BRS Safira proporciona elevada fecundidade de E. connexa e H. axyridis. O coccinelídeo H. axyridis prevalece como predador intraguilda na relação com E. connexa / Abstract: The aim was to evaluate biological aspects of Aphis gossypii in three colored cotton cultivars, to study the biology and interaction of the predator Harmonia axyridis and Eriopis connexa fed with the aphid A. gossypii reared on the cultivars, evaluate the density of trichomes and gossypol glands in leaves of cultivars and prepare life tables of A. gossypii, H. axyridis and E. connexa. The following colored cotton cultivars were used: BRS Rubi, BRS Safira and BRS Verde (Gossypium hirsutum latifolium Hutch Lr., herbaceous). The tests were conducted in climatized chamber at 25±2 ºC, RH 70± 10% and photophase of 12 hours. The feed substrates evaluated affected the nymphal stage of A. gossypii, and in BRS Verde observed the lowest duration and BRS Safira was the opposite. In BRS Verde with lowest density of trichomes observed high production of nymphs and the highest net reproductive rate (R0) by A. gossypii. The coccinellids E. connexa and H. axyridis had higher numbers of eggs with high viability when fed with aphids from BRS Safira, gossypol glands low density cultivar. The highest rate of cannibalism among larvae of E. connexa and H. axyridis was observed in BRS Verde. It was not observed predation on larvae of H. axyridis by E. connexa in all treatments. Therefore, BRS Safira cultivar supports the hightest fertility patterns of A. gossypii. The BRS Safira provides the high fecundity of E. connexa and H. axyridis. The coccinellid H. axyridis acts as intraguild predator in relation with E. connexa / Doutor