Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: John Byrne, School of Urban Affairs & Public Policy. Includes bibliographical references.

From all the species that arrive to a novel environment, very few manage to form a viable population. The guppy, a very successful invader, is a highly social species that performs some of its vital tasks (e.g., foraging, avoiding predators) in groups. This thesis aimed to quantify heterospecific association benefits that enhance invasion success. Interactions between invaders and natives could be one of the environmental characteristics of a place that increase its risk of invasion. I evaluated the tendency of an invasive species to associate with native individuals with similar ecological requirements. I tested the hypothesis that invaders gain exploring, acquisition of information and foraging benefits when socializing with natives. In these experiments I used the guppy as the invasive model species and endangered native Mexican topminnows (Poeciliopsis infans, Skiffia bilineata, Ameca splendens, Zoogoneticus tequila, Xenotoca eiseni and Girardinichthys viviparous). I found that guppies shoal with other species in Trinidad (Poecilia picta and Poecilia sphenops), where they are native (Chapter 2) and that this trait remains when they are invasive (Chapter 3). Guppies are equally willing to explore novel environments when accompanied by heterospecifics or conspecifics. Guppies are more willing to explore complex environments than simple ones. Moreover, when exploring simple environments they have a higher association tendency, regardless of the partner' species (Chapter 4), which could lead them to acquire the benefits of grouping behaviour and avoid Allee effects - the disadvantages of being part of a small group. In the contexts in which they were tested guppies gained as much information by associating with heterospecifics as with conspecifics (Chapter 5). Finally, I found that when shoaling in bigger shoals guppies are able to locate food faster and spent more time foraging. The benefits of increased shoal size were maintained when the additional guppies were replaced with heterospecifics. However, they derive more benefits from the species they are more willing to associate with (Chapter 6). These results uncover a mechanism enabling founding individuals to survive during the most vulnerable phase of an invasion and help explain why guppies have established viable populations in many parts of Mexico as well as in every continent except Antarctica.

Thesis (Ph. D.)--Washington State University, August 2008. / Includes bibliographical references.

Thesis (Ph.D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 325-365) Also available in print.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2009. / Härtill 4 uppsatser.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 196-218).

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2008. / Härtill 6 uppsatser.

European floodplain grasslands are characterized by periodic flooding and regular management, usually cutting and grazing as part of an agricultural system. Past losses and ecological degradation have been due largely to river regulation and either agricultural intensification or abandonment and have resulted in a substantial reduction in area across Europe. Nevertheless, the remaining resource supports considerable biodiversity and a high level of biological production. A better quantitative understanding of the functioning of these grasslands is required in order to establish effective conservation management within a sustainable land use system. The thesis examines the impact of key management factors on three important functional characteristics of the biodiversity of floodplain plant communities, namely plant diversity (measured by species diversity), cover (%) and primary production (above-ground biomass), on two floodplain grasslands of the River Trent, UK and a third on the the Luznice river, the Czech Republic. Field investigations of the effects of cutting, grazing, cessation of management, the influence of floodborne litter, and the impact of fertilizer nitrogen were undertaken over periods of between one and three seasons. These demonstrated that floodplain grassland plant communities are sensitive to variations in management and that impacts on communities are mediated particularly through effects on plant competition. Productive competitive species were encouraged both by abandonment and fertilizer application whereas cutting and grazing management, and the imposition of litter, favoured stress-tolerating perennials. Species diversity decreased both with high inputs of litter and additions of fertilizer. Plant community responses and competitive strategies of key species are discussed in the context of biodiversity conservation, ecological restoration and management of European floodplain grasslands.

Made available in DSpace on 2016-08-15T20:31:31Z (GMT). No. of bitstreams: 1 DarlanDAA_DISSERT.pdf: 1327863 bytes, checksum: 20f80b67329558ad38d3402c80b1f9c9 (MD5) Previous issue date: 2015-02-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / In the brazilian northeast due to seasonality of rivers and modest hydrological network, water security policy was established, based on the accumulation of water during the rainy season, through the reservoirs construction. This process generate human benefits, but also ecological consequences such as loss of aquatic biodiversity, change in the connectivity of water bodies and modification of biological processes such as reproduction and recruitment of species. In Apodi/Mossoró River basin , Leporinus piau Fowler,1941 is quite important for artisanal and subsistence fishing, however it is necessary to better understand their biology, to establish more effective conservation and management measures. In this context, the objective this work was to study the population structure and reproductive dynamics of Leporinus piau (Fowler, 1941), in the reservoir of Pau dos Ferros, Brazilian semiarid. Specimens were collected quarterly from February 2011 to November 2012 using gillnets. The specimens captured were counted and measured the standard length (cm), total weight (g), and dissected to identify sex, and gonadal maturity stage and weight of gonads (g). Were captured 555 individuals. The highest CPUE value was registered in May/2011 (0.0259 ind. m2*h) and lowest was in August/2012 (0.0008 ind. m2*h). The standard length ranged between 5.9 and 20.7cm and total weigh between 4.16 and 271.50g. The length class of 10-15cm was the most frequent of individuals captured for both sexes. The species presented isometric growth (b=3.01) and L50 was estimated to be 12.76cm. Of individuals captured, 276 were juveniles, 180 males and 99 females. The highest GSI value was observed in February/2011 for females (10.69) and males (5.72). There was a significant a positive correlation between GSI and rainfall. We conclude that the population of L. piau is established in the reservoir with some alterations its population attributes and reproductive period was determined between February and May / No nordeste brasileiro devido a sazonalidade dos rios e rede hidrológica modesta, foi estabelecida uma política de segurança hídrica, baseada na acumulação de água nos períodos de chuva, pela construção de reservatórios. Este processo gerou benefícios humanos, mas também consequências ecológicas, como a perda de biodiversidade aquática, alteração na conectividade dos corpos d água e modificação de processos biológicos como a reprodução e o recrutamento de espécies. No reservatório de Pau dos Ferros, bacia do Rio Apodi/Mossoró, a espécie Leporinus piau Fowler,1941, apresenta grande importância na pesca artesanal e de subsistência, no entanto é necessário conhecer melhor a sua biologia, para estabelecer medidas de conservação e manejo pesqueiro mais eficazes.Neste contexto, o objetivo do trabalho foi avaliar a estrutura da população e a dinâmica reprodutiva de L.piau no reservatório de Pau dos Ferros. As capturas foram feitas com redes de espera de diferentes malhas, entre 17h e 05h. Os peixes capturados foram contados, medidos o comprimento padrão (cm) e peso total (g) e dissecados para identificação do sexo e estágio de maturação gonadal. O maior valor de CPUE ocorreu em maio de 2011 (0,0259 ind. m2 * h) e o menor em agosto de 2012 (0,0008 ind. m2 * h). O comprimento padrão variou de 5,9 a 20,7cm e o peso de 4,16 a 271,5g. A classe de tamanho 10 a 15cm foi a mais frequente para os dois sexos. A espécie apresentou crescimento isométrico (b=3,01) e, L50 estimado em 12,76cm. Foram coletados 555 indivíduos, 276 jovens e 279 adultos, destes 180 machos e 99 fêmeas (1,81: 1)M:F. O maior valor de IGS ocorreu em fevereiro de 2011 para fêmeas (10,69) e machos (5,72). Houve correlação significativa e positiva entre IGS e pluviosidade. Concluímos que a população de L. piau está estabelecida no reservatório com alterações em seus atributos populacionais como a proporção sexual ou mesmo o comprimento de primeira maturação e o período reprodutivo ocorreu entre fevereiro e maio