I replicated a nesting study carried out 40 years ago in southern Utah to assess reasons for long-term population declines of mourning doves (Zenaida macroura) in the western United States. I compared current nesting patterns to similar data collected in 1952. I saw little difference in nest success and nest predation, but reproductive output and nest density decreased dramatically. The number of young fledged per pair of adults was only 64% of that estimated in 1952. A 1-2 week delay in the nesting season contributed to this decrease, but cannot explain it entirely. Nest density was about 20% of that in 1952 and total reproductive output for the study area about 12-19%. Underlying causes for these changes are uncertain, but patterns of delayed nesting, high nest abandonments, and low reproductive output are similar to those seen in stressed bird populations (e.g., food/nutrient limitation or increased toxicant levels). Finally, highest nest density occurred in a habitat type (i.e., Chalk Creek) considered unimportant for doves in 1952. Nests in Chalk Creek suffered higher predation and abandonment rates than those in irrigation ditches. I also examined the effect of perch sites on nest density and distribution in two ways. First, I demonstrated a significant correlation between nest density and perch s:te density in riparian plots. Second, I erected artificial perch sites in the second year of the study and recorded changes in nest densities. For the year of the study only, nest density was higher in the experimental plots, but the difference was not statistically significant. From the levels recorded the previous year, however, nest densities increased in the experimental plots and decreased in the control plots. This difference was statistically significant, suggesting that mourning doves use the presence of perch sites as cues for habitat selection. Finally, in comparing the presence of other avian species, I found significantly more blackbirds (Aqelaius phoenicus and Euphaqus cyanocephalus) and western meadowlarks (Sturnella neglecta) in experimental plots than in control plots.

No description available.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 149-168). Also available on the World Wide Web.

Coral reefs are in global decline, with seaweeds increasing as corals decrease. Though seaweeds have been shown to inhibit coral growth, recruitment, and survivorship, the mechanism of these interactions is poorly known. Here we use field experiments to show that contact with four common seaweeds induces bleaching on natural colonies of Porites rus. Controls in contact with inert, plastic mimics of seaweeds did not bleach, suggesting treatment effects resulted from allelopathy rather than shading, abrasion, or physical contact. Bioassay-guided fractionation of the hydrophobic extract from the red alga Phacelocarpus neurymenioides revealed a previously characterized antibacterial metabolite, Neurymenolide A, as the main allelopathic agent. For allelopathy of lipid soluble metabolites to be effective, the metabolites would need to be deployed on algal surfaces where they could transfer to corals on contact. We used desorption electrospray ionization mass spectrometry (DESI-MS) to visualize and quantify Neurymenolide A on the surface of P. neurymenioides and found the metabolite on all surfaces analyzed. The highest concentrations of Neurymenolide A were on basal portions of blades where the plant is most likely to contact other benthic competitors.

No description available.

The causes of recent episodes of forest decline in Canada have not yet been fully determined. Current explanations include the effects of acid depositon as well as natural causes such as climate stress. This thesis takes a geographic approach and undertakes risk-response comparisons in order to examined the problem of maple forest dieback in the Appalachian region of Quebec. Geographic Information Systems are used to map a series of forest decline risk factors relating to soil characteristics and topography. The individual risk factors, as well as models comprising weighted combinations of risk factors, are compared with actual defoliation patterns. Forest defoliation is determined using areal survey data and satellite imagery. Although statistically significant associations were obtained between defoliation patterns and several risk factors, the amount of association was not strong enough to conclude that these factors are dominant causes of forest decline.

One of the three largest systems of black-tailed prairie dog (BTPD) colonies is located in northwestern Chihuahua, Mexico. During the last two decades, the area occupied by these colonies has been highly reduced and fragmented. Previous studies suggested that agriculture, poisoning, cattle overgrazing and shrub encroachment could be the factors responsible for such declines. However, the severe drought occurring in the region between 1994 and 2004 has not been considered in this equation. Because these populations occur in arid regions at the southern edge of the species range, they could be especially sensitive to changes in plant productivity. Furthermore, fragmentation of colonies may accelerate population declines due to size and isolation effects. In this study, I analyzed species-habitat relationships at different spatial and temporal scales to understand the causes of recent declines of BTPDs in northwestern Chihuahua. The most severe loss of colony area and most local extinctions occurred between 1988 and 2000, but most likely before 1997. Extinction of colonies before 2000 mostly occurred at small and isolated colonies in low-productivity areas. The coincidence of greatest area decline with the occurrence of most intense drought suggests a prominent role of drought in the population collapse. Overall, patterns of BTPD occurrence and abundance in Chihuahua are greatly influenced by spatial and temporal variation in forage cover. Although BTPDs were more likely to occur in open areas with short vegetation, increased forage cover positively predicted occurrence. High levels of forage cover during the dry season were positively related with BTPD density, juvenile production and population rate of change, but forage cover during the preceding rainy season was a negative predictor of demographic indices. High plant productivity during humid periods seems to have negative impacts on BTPD populations, presumably because the rapid plant growth reduces visibility and predator detection by BTPDs. The most influential landscape variable was the effective isolation of colonies. Although increased isolation may reduce the probability of occurrence at a given site, highly isolated locations may support high population densities. Contrary to my original predictions, I did not detect significant impacts of human-related factors on BTPD distribution and abundance. / Ecology

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 53-58). Also available on the World Wide Web.

The increased honey bee colony losses in the last decade gain a considerable attention of scientists and public. The causes of these losses include a wide range of biotic and abiotic factors, but pathogens and parasites are probably the main ones. Monoxenous trypanosomatids in honey bee gut Lotmaria passim and Crithidia mellificae were neglected for a long time but according to recent studies they seem to participate in those colony declines. Trypanosomatids are widespread parasites, including also the causes of some human illnesses, such as sleeping sickness, Chagas disease and leishmaniasis. The mechanism of the effect on honey bee health is not well understood so far. The aim of this thesis was to verify the occurrence of the trypanosomatids in honey bee samples from two regions in Czech Republic. The methods, based on detection of specific DNA loci, confirm the high prevalence of L. passim, which was founded in majority (71 %) of the samples. On the contrary, no samples were positive to C. mellificae.

Orientadores: Paulo Inacio de Knegt Lopez de Prado, Carlos Roberto Sorensen Dutra da Fonseca / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-08T17:25:56Z (GMT). No. of bitstreams: 1 Becker_CarlosGuilherme_M.pdf: 2929831 bytes, checksum: 6d4d242a4fbe6aac18c4546b538bce05 (MD5) Previous issue date: 2007 / Resumo: O nicho dos anfíbios muda drasticamente ao longo da ontogenia, forçando larvas e pós-metamórficos a ocuparem dois hábitats distintos. Em áreas desmatadas, sítios reprodutivos aquáticos e fragmentos florestais podem ser muito desconectados, isolando o hábitat dos girinos do hábitat dos adultos, em um padrão de fragmentação que chamamos de desconexão de hábitats. Neste estudo, avaliamos os impactos da desconexão de hábitats sobre os anfíbios (i) através de migrações reprodutivas e de padrões de abundância populacional dos anfíbios com larva aquática entre fragmentos com e sem riachos em uma paisagem fragmentada de Mata Atlântica; (ii) através do uso diferencial de hábitat por diferentes guildas nesta mesma paisagem; (iii) por meio de uma análise macroecológica avaliando o efeito da desconexão entre riachos e fragmentos florestais sobre anfíbios de serrapilheira ao longo de 13 pontos na Mata Atlântica. Em nível populacional, detectamos um forte padrão de migração dos anfíbios florestais com desenvolvimento larval aquático entre fragmentos sem riachos e os riachos da matriz de pastagem. Estas espécies foram dramaticamente mais abundantes em fragmentos com riachos do que sem riachos. A estrutura de comunidades variou consistentemente entre hábitats, sendo a guilda das espécies florestais de desenvolvimento larval aquático a mais prejudicada pela desconexão. Tratando-se de grande escala geográfica, a desconexão de hábitat foi o único atributo da paisagem afetando negativamente a riqueza de espécies com desenvolvimento larval aquático, enquanto que a perda de habitat teve influência negativa somente nas espécies com desenvolvimento direto. Estes resultados sugerem que paisagens com altas taxas de desconexão entre fragmentos florestais e sítios reprodutivos têm maior chance de sofrerem declínios populacionais, especialmente de anfíbios associados à floresta e com desenvolvimento larval aquático. Estratégias de conservação em qualquer país devem considerar o fortalecimento das leis, tendo em mente a importância das matas de galeria e a configuração de cada paisagem, minimizando a desconexão entre hábitats florestais e os sítios reprodutivos dos anfíbios / Abstract: The niche of amphibians changes drastically along the ontogeny, forcing larvae and post-metamorphics to occupy two distinct habitats. In deforested areas, aquatic breeding sites and forest fragments can be far apart, isolating the habitat of tadpoles from the habitat of adults, in a landscape pattern we call habitat-split. In this study, we evaluated the impacts of habitat-split on amphibians (i) through breeding migrations and abundance patterns of species with aquatic larvae between fragments with and without streams in a severely fragmented landscape of Brazilian Atlantic Forest; (ii) by the habitat use of different guilds in this landscape; (iii) through a macroecological analysis, evaluating the effect of habitat-split on litter-amphibians throughout 13 Atlantic Forest sites. At the population level, we detected a migration pattern for the stream-breeding forest amphibians between the fragments without streams and the streams of adjacent grass fields. These species were dramatically more abundant in fragments with streams than in fragments without streams. The community structure varied consistently across habitats, being the guild of forest-associated species with aquatic larvae the most affected by habitat-split. At a larger geographic scale, habitat-split was the only landscape attribute negatively affecting the richness of species with aquatic larval stage, whereas habitat loss had negative influences on direct development species only. These results suggest that landscapes with high mismatches between forest fragments and breeding sites are more prone to experience population declines, especially of forest-associated amphibians with aquatic larval stage. Conservation strategies in any country must regard the law reinforcement, considering the importance of riparian buffers and the configuration of each landscape, minimizing the mismatch between non-reproductive habitats and breeding sites for amphibians / Mestrado / Ecologia / Mestre em Ecologia