Thesis (Ph. D.)--Ohio State University, 2009. / Title from first page of PDF file. Includes bibliographical references (p. 151-168).

Ecosystems across the globe are facing a range of anthropogenically-driven changes, including biotic invasions, urbanisation and land-use alterations, which can affect ecosystem structure and stability. To manage both native species decline and invasive species spread it is imperative that we can accurately predict how current global environmental change will affect biotic communities. I examined effects of different land uses at both landscape- and habitat-scales on native (Culex pervigilans) and exotic (Aedes notoscriptus) mosquito distributions in lentic (standing water) freshwater habitats. Because of the importance of land use on habitat characteristics, I expected different land uses would contain different biotic communities, and that mosquitoes would more likely be present in simple communities with fewer predators. Moreover, because habitat disturbance and modification can significantly influence community structure, I expected less diverse pond communities in habitats within highly modified urban and pasture land uses would also be more likely to contain mosquitoes. I found land use affects mosquito presence, and was likely strongly linked with land-use effects on predator presence and taxon richness. Predators were more common in habitats within native forest and tussock grassland, and mosquitoes were almost entirely restricted to urban and pasture habitats. Moreover, local habitat characteristics had a strong influence on both mosquito and predator presence, with deeper and more open habitats supporting greater predator abundance, thereby excluding mosquito larvae. To further investigate the global of climate change on predator-prey interactions involving Ae. notoscriptus and Cx. pervigilans, I conducted two experiments. Firstly, I measured effects of habitat warming and short- and long-term habitat drying on interactions between the two mosquito species and three predatory invertebrates, Anisops wakefieldi backswimmers, Austrolestes colensonis damselflies, and Procordulia smithii dragonflies, which represented predators characteristic of different habitat drying regimes. A second experiment further tested interactions between A. wakefieldi and the two mosquito species in a wider range of temperatures. There was little evidence that short-term habitat drying affected interaction strengths of any of the predator-prey combinations, but strong evidence for the importance of temperature-mediated predation rates which depended on both predator and prey identities. Here, predators characteristic of more temporary hydroperiods showed temperature-mediated predation responses on the two mosquito species: increasing temperature resulted in greater predation on native Cx. pervigilans but not effect on predation on exotic Ae. notoscriptus. The second experiment revealed, again, that predation depended on both temperature and mosquito species with higher predation occurring at increased temperature, but also indicated life history traits could mediate the overall effect of temperature-mediated predation. Overall, I have shown that interactions between temperature, predator identity and mosquito species will be very important in determining the potential for mosquitoes to invade under a changing climate. Considering effects of both climate change and land-use-driven habitat modification on the invasion potential of mosquitoes in freshwater communities will therefore be important for managing both native species decline and spread of invaders. Moreover, research and management decisions on critical species like mosquitoes will need to encompass multiple drivers of climate change at both global and local scales.

Theses (M.S.)--University of New Hampshire (Dept. of Zoology), 2007. / Includes bibliographical references. Also available online.

Thesis (Ph.D.) -- University of Montana, 2008. / Title from author supplied metadata. Description based on contents viewed on July 6, 2009. Includes bibliographical references.

Thesis (M.M.S.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 93-105.

Thesis (Ph.D.)--University of Waikato, 2009. / Title from PDF cover (viewed July 10, 2009) Includes bibliographical references (p. 316-340)

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 109-127.

No description available.

Made available in DSpace on 2014-06-11T19:35:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-23Bitstream added on 2014-06-13T18:47:09Z : No. of bitstreams: 1 zarzuela_mfm_dr_rcla.pdf: 1561827 bytes, checksum: 5f6e6346568cb3b53c71ae3cf3d825c1 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Algumas espécies de formigas proporcionam impacto severo nas comunidades que invadem. Quando entram em contato com áreas urbanizadas e com o homem seus prejuízos podem ser ainda maiores. A exemplo pode-se citar: Solenopsis spp.; Linepithema humile; Wasmannia auropunctata; Pheidole megacephala e Paratrechina spp.. Muitas são as tentativas de controlar essas espécies, no entanto nem sempre se obtém sucesso. O controle biológico é uma alternativa para o controle químico e vem ganhando grande destaque em pesquisas. Os principais organismos utilizados no controle biológico de insetos são os fungos e os nematóides. Esse trabalho teve como objetivo esclarecer algumas das frequentes dúvidas no que diz respeito ao controle biológico de formigas, como avaliar a presença de entomopatógenos em colônias de formigas invasoras em áreas onde suas populações estão em equilíbrio e nas áreas infestadas; aplicar entomopatógenos em colônias de Monomorium floricola em condições de laboratório para avaliar a eficiência destes agentes no controle de espécies urbanas bem como observar o comportamento destas formigas frente a esses microrganismos. Foram isolados os nematóides entomopatogênicos Heterorhabditis sp. e Steinernema sp. e os fungos Beauveria bassiana Metarhizium anisopliae e Paecilomyces sp. Estes microrganismos estão presentes em colônias de formigas invasoras em áreas onde suas populações estão em equilíbrio e nas áreas infestadas. As colônias que receberam a aplicação de Steinernema sp. e Heterorhabditis sp. tiveram uma mortalidade de operárias maior que as do controle. O fungo Beauveria bassiana apresentou maior mortalidade de operárias da espécie M. floricola. Porém, não houve redução nem eliminação das colônias em nenhum dos tratamentos. Os comportamentos de defesa das formigas, a exemplo do comportamento de limpeza e o comportamento de fuga dos ninhos... / Some ant species provide severe impact on the communities they invade. When they come into contact with urban areas and man its losses may be even greater. The ants Solenopsis spp.; Linepithema humile; Wasmannia auropunctata, Pheidole megacephala, Paratrechina spp. can be cited. There are many attempts to control such species, although not always succeed. Biological control is an alternative to chemical control and has gained great prominence in research. The main organisms used in biological control of insects are fungi and nematodes. This study aimed to clarify some questions regarding the biological control of ants. Invasive ant species occurring in some regions of Brazil, in areas where their populations are in balance and in infested areas, were evaluated for the presence of entomopathogenic in their colonies. Moreover, entomopathogenic were applied in colonies of Monomorium floricola under laboratory conditions to evaluate the effectiveness of these agents on the control of urban species. The behavior of the controlled ants was evaluated. The entomopathogenic nematodes Heterorhabditis sp. and Steinernema sp. and the fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces sp. were isolated. These microorganisms are present in colonies of invasive ants in areas where their populations are in balance and in infested areas. The colonies that received the application of Steinernema sp. and Heterorhabditis sp. showed a higher mortality of workers than control. The fungus Beauveria bassiana showed higher mortality of M. floricola workers. However, no colony reduction or elimination were observed in any treatments. The defensive behaviors of ants, such as grooming behavior and nest escape must be considered for the use of fungi and nematodes as a form of biological control.

The success of an invasive alien species is often attributed to the ecological advantage gained from natural enemy release. Numerous factors have been suggested as contributing to the success of Harmonia axyridis as an invasive alien species, including enemy release. This thesis studied the interactions of several parasites with H. axyridis, investigating parasite transmission, growth and virulence as well as host immune responses, thereby shedding light on the potential role of enemy release in the invasion biology of this ladybird. Benefits gained by invasive alien species from enemy release diminish if parasites of native species shift hosts to exploit the novel invader. The fungal ectoparasite Hesperomyces virescens began infecting H. axyridis shortly after it invaded the UK, probably as a result of a host shift from Adalia bipunctata. This study found a rapid increase in H. virescens prevalence over three years in London H. axyridis populations. Laboratory study showed H. virescens transmission and growth to be more efficient on A. bipunctata than the novel host. In addition, reciprocal interspecific transfers of H. virescens strains isolated from A. bipunctata and H. axyridis revealed that the infection characteristics of the fungi from these two hosts differed, suggesting strains may have diverged after the initial shift from A. bipunctata to better exploit the host from which they were derived. Laboulbenialian fungi were previously thought to have negligible impacts on host fitness. A detailed examination of H. virescens infecting H. axyridis found distinct virulence, with infections resulting in a 50% reduction in host lifespan. In addition, chronic H. virescens infection in males caused acceleration in the age-associated decline in body condition while for females, infection triggered fecundity senescence and a faster age-related decline in fertility. While their role in accelerating ageing is debated, the results presented here provide evidence that infectious diseases can drive the ageing process in this insect species. In nature, multiple parasites affecting a single host are common. The effect of co-infection on the virulence caused by two fungal infections was characterised using H. axyridis and A. bipunctata hosts. The ability of two ladybird species to defend against an acute fungal parasite, while infected with the relatively avirulent H. virescens was found to be sex-specific. While for females, the presence of co-infection did not alter the virulence seen in singly infected females, a higher mortality rate existed for co-infected males compared with those infected singly. Previously, H. virescens has been considered to be avirulent, however, this study provides evidence that this chronic fungal parasite may be important when considering the mortality associated with co-infections in the field. The invasive success of H. axyridis has, in part, been attributed to a more vigorous immune ability compared with other competitor species. Previously, field studies have shown that the prevalence of the parasitoid wasp Dinocampus coccinellae in H. axyridis is considerably lower than in the UK primary host of this wasp, Coccinella septempunctata. The extent to which the prevalence asymmetry in the field is driven by differences in host encapsulation response was tested by first comparing the encapsulation ability of C. septempunctata and H. axyridis directed against an artificial implant. Following this, the encapsulation response of D. coccinellae parasitized individuals was assessed and compared between the two host species. While encapsulation ability did not differ between the host species, and D. coccinellae did not affect the immune response of H. axyridis, wasp parasitism did alter the encapsulation ability of C. septempunctata, although it was inconsistent across sexes and populations. Overall, this thesis furthers our understanding of the fungal parasite H. virescens and its association with the notorious invader H. axyridis. The research presented here also demonstrates the use of H. axyridis as a model system in areas other than invasion ecology and furthermore, contributes to understanding the role of infectious disease in the rate of ageing. Finally, sex-specific effects were found across the chapters of this thesis, demonstrating the use of H. axyridis in the study of sex-specific effects of infections.