Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye.

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye. / Forestry, Faculty of / Graduate

No description available.

<p>Modern economic activities, like industry and agriculture, as well as household activities, generate an important amount of refuse. The way we collect, transport, and dispose it will determine the level of environmental contamination. May animals exploit refuse as a food source (i.e., anthropogenic food subsidy) and gulls are the most important group. Refuse subsidizes energetically gull populations, which impacts on their acquisition and allocation of resources, as well as on the environment, with ecological and evolutionary consequences are not well understood. In this dissertation we evaluated potential impacts of refuse on gulls by doing a literature review as well as empirical research on the Kelp Gull (<i>Larus dominicanus</i>) in the Rio de la Plata Estuary in South America. Direct and indirect impacts of refuse on gull species and the environment have been observed during the review process. We have detected positive impacts of refuse on body size, chick growth, fecundity, reproductive success, and population dynamics. However, negative impacts were also found focusing on fecundity, reproductive success, and population dynamics. Indirect negative impacts on other species, water bodies, and airport security were also found. Refuse produces numerous impacts on gulls at the individual, population, and species levels, with indirect negative consequences on ecosystems. There is a need to reduce the access of gulls to sources of refuse to mitigate the existing and potential conflicts with human activities and other species, especially those that are threatened and endangered. During our empirical research we found that refuse was ingested and assimilated by Kelp Gull chicks during the chick rearing period and that the ecological niche width increased with the age of the chick. We propose that parents incorporate isotopically unique food sources to nestling’s diet during their growth, increasing isotopic diversity of nestlings. Additionally, we found that refuse could affect foraging decisions of females during the pre-incubation period, which could positively affect future fecundity and negatively impact reproductive success. We found also that refuse consumption on fecundity and reproductive success of gulls is generally studied at the colony level, using conventional diet techniques, but not much has been done using stable isotopes at the individual level, making comparisons among studies and conclusions difficult to address. We encourage other researchers to continue incorporating the isotopic ecology perspective to study the effect of food subsidies on gulls. Additionally, we found that Kelp Gull on the coast of the Rio de la Plata Estuary ingest plastic debris. We conclude that plastic bags and plastic films might be the most important source of contaminants for the Kelp Gull on the coast of the estuary. Main findings of this dissertation suggests the need for an improvement of waste management practices and a regulation of plastic production and use in Uruguay to reduce plastic ingestion by gulls. Finally, next steps for research are provided in this important area of environmental science and natural resource management.</p>

Invasive non-indigenous species are among the principle drivers of global change, altering nutrient cycles, changing disturbance regimes, and generally threatening biodiversity. Climate change is widely expected to exacerbate invasions by relaxing abiotic barriers, such as low temperature, but the mechanistic evidence supporting this is limited. Here, I evaluate the hypothesis that low temperatures determine the northern range limit of kudzu (Pueraria montana var. lobata), an invasive Asiatic vine in North America, by assessing freezing and chilling tolerance of kudzu plants in winter, spring, summer, and fall. Kudzu was widely planted throughout the southeastern U.S. in the early 20th Century to prevent erosion. It is winter-deciduous and reproduces primarily from buds on stem nodes. In the last 40 years, kudzu has migrated northward in concert with a northward shift in the -20oC minimum winter temperature isocline, indicating that less severe winter cold is permitting northward migration. Freezing mortality during winter does not explain this correlation. Electrolyte leakage assays demonstrate that above- and belowground kudzu stems can survive to -27oC and -17oC. Insulation provided by soil and snow protects belowground stems from lethal temperatures to well north of kudzu's current range limit. Severe spring chill stops growth and photosynthesis and causes some shoot mortality, but both growth and photosynthesis recover quickly following the chill. Summer growth rates are rapid (up to 22 cm/d), responding within hours to temperature changes, and are unimpaired by nighttime lows. Photosynthesis is reduced at cool temperatures, but on cool days, kudzu leaves tend to be warmer than air temperature, so photosynthesis rates generally remain close to optimal values. In autumn, growth stops below 15oC, but leaves are retained and maintain modest photosynthetic competence until killed by frost in November. In colder climates that occur far north of kudzu's current range, reductions in the length and quality of the growing season could accumulate over time to reduce kudzu's success. There is, however, no strong evidence that low temperatures in any season will prevent kudzu from migrating throughout southern Ontario, making kudzu a good candidate for invasive species regulations.

Invasive non-indigenous species are among the principle drivers of global change, altering nutrient cycles, changing disturbance regimes, and generally threatening biodiversity. Climate change is widely expected to exacerbate invasions by relaxing abiotic barriers, such as low temperature, but the mechanistic evidence supporting this is limited. Here, I evaluate the hypothesis that low temperatures determine the northern range limit of kudzu (Pueraria montana var. lobata), an invasive Asiatic vine in North America, by assessing freezing and chilling tolerance of kudzu plants in winter, spring, summer, and fall. Kudzu was widely planted throughout the southeastern U.S. in the early 20th Century to prevent erosion. It is winter-deciduous and reproduces primarily from buds on stem nodes. In the last 40 years, kudzu has migrated northward in concert with a northward shift in the -20oC minimum winter temperature isocline, indicating that less severe winter cold is permitting northward migration. Freezing mortality during winter does not explain this correlation. Electrolyte leakage assays demonstrate that above- and belowground kudzu stems can survive to -27oC and -17oC. Insulation provided by soil and snow protects belowground stems from lethal temperatures to well north of kudzu's current range limit. Severe spring chill stops growth and photosynthesis and causes some shoot mortality, but both growth and photosynthesis recover quickly following the chill. Summer growth rates are rapid (up to 22 cm/d), responding within hours to temperature changes, and are unimpaired by nighttime lows. Photosynthesis is reduced at cool temperatures, but on cool days, kudzu leaves tend to be warmer than air temperature, so photosynthesis rates generally remain close to optimal values. In autumn, growth stops below 15oC, but leaves are retained and maintain modest photosynthetic competence until killed by frost in November. In colder climates that occur far north of kudzu's current range, reductions in the length and quality of the growing season could accumulate over time to reduce kudzu's success. There is, however, no strong evidence that low temperatures in any season will prevent kudzu from migrating throughout southern Ontario, making kudzu a good candidate for invasive species regulations.

<p>This dissertation examines issues concerning sap flux scaled estimates of the canopy-averaged transpiration rate of trees per unit leaf area (E_L) and stomatal conductance (G_S), as well as their implications in the water and carbon balance of individuals and stands, with the final goal of an integrated assessment of 11 years of such data from two species (<italic>Pinus taeda</italic> and <italic>Liquidambar styraciflua</italic>) at the Duke Free Air Carbon dioxide Enrichment (Duke FACE) facility. These issues include (1) the effects of allometric relationships and xylem characteristics on the gas phase transport of water from leaves and the hydraulic supply of it, (2) consideration of the hydraulic capacitance in the inference of stomatal behavior from sap flux data and (3) the dynamic modeling of stomatal conductance to environmental drivers using Bayesian techniques. It is shown that a) for resolution of sap flux in conifers at the scale of minutes under dynamic conditions, time constants for both stomatal responses and hydraulic capacitance of sapwood must be considered, (b) nighttime conductance can lead to large errors in rates of sap flux measured under some conditions, (c) variation in allometry between <italic>P. taeda</italic> individuals can lead to different rates of transpiration and carbon assimilation per unit leaf area and that (d) hydraulic time constants for the stems of mature <italic>P. taeda</italic> at Duke FACE trees varied by the stem length considered and were on the order of 30-45 minutes for a 10-m segment. An analysis incorporating all these elements leads to the conclusions that (e) both elevated CO₂ (eCO₂) and fertilization (FR) resulted in proportionally larger reductions in the E_L and G_S of P. taeda as soil moisture decreased with (f) eCO₂ having little to no effect in months of high soil moisture and (g) FR leading to ~14% reduction of GS under high soil moisture in absence of eCO₂, while (h) both eCO₂ and FR led to reduced E_L and G_S of <italic>L. styraciflua</italic> across soil moisture conditions.</p> / Dissertation

The biogeographic distribution of organisms is determined by physiological characteristics that enable a population to persist in a specific location. Global climate change effects are anticipated to increase the physiological stress experienced by organisms. Consequently, it is important to understand physiological responses to environmental stress and the mechanisms used by animals to cope with variable conditions. I investigated the physiological response to environmental stress in two species of mussel from New Zealand, Perna canaliculus and Mytilus galloprovincialis, using quantitative PCR and ecological field experiments. A series of laboratory and field experiments were done to manipulate stress levels and the expression levels of three heat shock protein genes (hsp24, hsp70, hsp90) were measured. A transcription regulatory gene (elf2) and a cell cycle regulatory gene (tis11d) were also measured. The dynamics of stress response gene expression in response to acute stress and gene expression changes in the natural population due to varying forms of environmental stress were tested. Between-zone translocations of different sized M. galloprovincialis and P. canaliculus were done at two sites in both east and west regions of the South Island of New Zealand. Site was found to be the most important factor in stress response. Apparent low food and high exposure stress interacted to create the particularly elevated stress response at the Timaru site. The adaptive ability of mussels transplanted between sites with varying environmental conditions was also tested. Results suggest that acclimation may be limited under stressful conditions. Furthermore, I found that P. canaliculus, the predominantly low-zone species, had a lower stress response than M. galloprovincialis, which was contradictory to predictions. The investigations described in this thesis suggest that interactive effects of abiotic stress and food limitations are particularly challenging for animals. With the severity of climate change scenarios predicted, changes in water quality and aerial and seawater temperature suggest mussel populations are likely to be negatively affected in the future. This work also illustrates the great potential to utilise molecular techniques for analysis of physiological processes of non-model organisms in a real-world setting.

Made available in DSpace on 2016-12-23T13:48:25Z (GMT). No. of bitstreams: 1 Fabiola Chrystian O Martins.pdf: 4446449 bytes, checksum: 0a2a581f0cb5f1b06db38bac7f66b462 (MD5) Previous issue date: 2006-02-22 / The physiological ecology responses of periphyton in the high course of the Santa Maria da Vitória (ES) river had been evaluated during one year, in two stations. The determined environmental variables had been: temperature, transparency, euphotic zone, depth, pH, OD, electric conductivity, STD, NO2 -, NO3 -, total-N, PO4 - and total-P. The Periphyton in natural substratum was evaluated through the biomass, chemical composition and structure of the algae community and classified through the autotrophic and Lakatos indexs. The river presented acid to slight acid waters, low electric conductivity and STD. OD, transparency and euphotic zone was raised. The total-N was high, had been compared with the ones of P, resulting in raised ratio NT/PT, evidencing an environment limited for P. The ACP showed distinction between the stations. It had difference of the periphytic biomass between the two stations explained, mainly, for the availability of nutrients. They had been registered 147 taxa of algae. Zygnemaphyceae was the Class most representative, qualitatively, in the station 1 and Cyanophyceae and Euglenophyceae in station 2. Bigger density was attributed to the Bacillariophyceae in the station 1 and Cyanophyceae in station 2. Zygnemaphyceae presented greater biovolume in the station 1 and Bacillariophyceae in station 2. During all the sampling period, in both the stations, the community was classified as heterotrophic and of low biomass. Station 1 presented trend to the trophic degree minor if compared station 2. This difference was the main factor that influenced the biomass and structure of the algae community, that if it showed limited, mainly, for P. / As respostas ecofisiológicas do perifíton no alto curso do rio Santa Maria da Vitória(ES) foram avaliadas durante um ano, em duas estações. As variáveis abióticas determinadas foram: temperatura, transparência, zona eufótica, profundidade, pH, OD, condutividade elétrica, STD, NO2 -, NO3-, N-total, PO4-, P-total. O perifíton em substrato natural foi avaliado através da biomassa, composição química e strutura da comunidade de algas e classificado através dos índices autotrófico e de Lakatos. O rio apresentou águas ácidas a levemente ácidas, baixa condutividade elétrica e STD. OD, transparência e zona eufótica foram elevados. As concentrações de Ntotal também foram altas, comparadas às de P, resultando em elevada razão NT/PT, evidenciando um ambiente limitado por P. A ACP mostrou distinção entre as estações. Houve diferença da biomassa perifítica entre as duas estações explicadas, principalmente, pela disponibilidade de nutrientes. Foram registrados 147 táxons de algas. Zygnemaphyceae foi a Classe mais representativa, qualitativamente, na estação 1 e Cyanophyceae e Euglenophyceae na estação 2. Maior densidade foi atribuída à Bacillariophyceae na estação 1 e Cyanophyceae na estação 2. Zygnemaphyceae apresentou maior biovolume na estação 1 e Bacillariophyceae na estação 2. Durante todo o período amostral, em ambas as estações, a comunidade foi classificada como heterotrófica e de biomassa baixa. A estação 1 apresentou tendência à menor trofia se comparada a estação 2. Essa diferença foi o principal fator que influenciou a biomassa e estrutura da comunidade de algas, que se mostrou limitada, principalmente, por P.

Despite of the documented impacts of the so-called green revolution, food security in the world faces new challenges in terms of population growth, increases in no-agricultural land use (urbanization), and climate change. Trends in food security show that the world community is operating within two limits of food system: (i) the quantity of food that can be produced under a given climate; and (ii) the quantity of food needed by a growing and changing population. Therefore, taking food security successfully into the future requires novel approaches to boost agricultural productivity in order to balance food supply and demand without expanding the agricultural land. To date, progress in wheat yield has been largely the result of the development of dwarf varieties through introgression of reduced height (Rht) genes. The height reductions arising from the presence of these genes increased yield by alteration of partitioning of dry matter and nitrogen in favour of the spike. However, increased partitioning through additional reductions in plant height is not likely; as comparative studies indicate that wheat yield is reduced when plants are shortened beyond a threshold, and most of the modern cultivars have reached the optimal height. Therefore, this dissertation aimed to identify the physiological attributes able to produce yield increases in the Rht genotypes with the optimal heights. Approaches based on physiological understanding of yield are necessary for developing genotypes combining high yielding potential and agronomic traits of superior adaptation, and for understanding yield limiting factors. Yet, direct measurement of physiological variables is often difficult or expensive; as an example, measuring plant water status in the field is problematic, with techniques such as psychrometry generally only being suitable for laboratory studies. Therefore, proxy such as tissue RWC may be a good alternative measure of plant water status. We aimed to address these questions with three components of experimental research :(i) proxy-based screening to increased photosynthetic rate and water use efficiency in wheat; (ii) determinants of increased HI in lines with different Rht genes (b, c) when incorporated into contrasting background wheat genomes (B, D), and the relative effect on N partitioning during grain filling; (iii) analyses of stable isotopes (δ²H, δ¹⁸O, δ¹⁵N and δ¹³C) in an agronomic perspective in alley cropping systems associated with adjacent N₂ fixing trees, in terms of hydraulic redistribution, N availability and crop yields. In this thesis, the proxy-based approach to crop selection was defined as a surrogate-based (proxy and surrogate used interchangeably) screening of cultivars for morphological, anatomical, and physiological traits of performance or crop environmental responses. The research proposed steps for conducting a proxy-based crop selection programme. A comparative screening of 23 Eps cultivars and ranking for traits of photosynthetic and water use efficiency showed the correlative relationships of SLA to An, WUEi, leaf N, Δ¹³C, Kh, leaf RWC, and IVD. Additionally, it was observed that IVD may influence WUE and Amax. It was suggested that these relationships of SLA to traits of photosynthesis possibly resulted from the association of SLA and the leaf biochemical characteristics. Attention was also given to examining the mechanistic foundations that determine the relationship between plant height and yield. The results showed the straw-shortening significantly correlated both with Amax and Kh; and SLA decreased with the level of dwarfing; and the Amax related both Kh and SLA. Therefore, it was proposed that the straw-shortening may affects Amax by exerting a controlling influence over Kh through SLA. Moreover, both the partitioning of N to spike and the flag leaf N were related to plant height and growth stage. Additionally, the increased post-anthesis partitioning of N to grain associated with high N uptake rate and high MRT of N were probably the traits behind increased NUE and NHI. The data also indicated that increased grain number per spike, kernel weight and reduced peduncle length might be the driver of the increased HI in this experiment. The test of the hypothesis that there might be practical application of the analyses of the natural abundance of stable isotopes (δ²H, δ¹⁸O, δ¹³C, and δ¹⁵N) and isotopic mixing model by IsoSource to understand plant interactions in terms of water redistribution and nitrogen transfer and uptake in agroforestry systems, indicated a consistent gradient in depletion of wheat xylem water δ²H, δ¹⁸O, and δ¹⁵N in leaf as moving further away from the tree line. The data also reflected a consistent pattern of isotopic values (δ²H, δ¹⁸O, and δ¹⁵N) in wheat in the proximity of the tree being similar to that of the tree, suggesting they were using the same source of water and N. Similarly, an isotopic mixing model data showed that the crops in the proximity of the trees accessed considerably amounts of the water and nitrogen redistributed by trees. The study also indicated the improvement in water use efficiency, chlorophyll content, grain number per spike, and grain yield for the crops nearest to the trees for a distance up to 5 m. In conclusion, selection for increased HI should shift focus from reduced plant height to include increased grain number and kernel weight, increased partitioning of N to spike, reduced peduncle length, and low SLA. Finally, the hypothesis that efflux of water and N in agroforestry system from tree roots in topsoil and influences a number of physiological functions of neighbouring crops was confirmed by isotopic and physiological data.