京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21631号 / 医博第4437号 / 新制||医||1034(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 川上 浩司, 教授 松田 文彦, 教授 黒田 知宏 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The brown bear (Ursus arctos) is a generalist omnivore that occupies diverse habitats and displays high levels of behavioral plasticity. Plasticity in foraging behavior can result in variable diets across a population, and allow individuals to use a greater variety of resources. The distribution of food in space and time may also be an important factor in determining brown bear resource selection as it can greatly influence foraging efficiency. Our objectives were to determine if seasonal brown bear home ranges were influenced by temporal availability and spatial distribution of resources and if deviation from an optimal diet influenced brown bear body condition. Understanding how the spatial and temporal distribution of food influences brown bear space use and the relationships between behavioral plasticity and the ability of populations to persist in dynamic environments could provide additional insights into the eco-evolutionary advantages of variable foraging behavior and ultimately population resilience.

Climate change can alter the ecology of natural systems through various mechanisms, such as direct thermal effects on a consumer. However, consumers may employ behavioral mechanisms in response to warming. Among these may be spatial or temporal shifts in activity, making use of thermal heterogeneity on the landscape. Despite this, few studies consider the role of behavioral plasticity and spatial or temporal heterogeneity in the context of climate change. I conducted experiments to evaluate the importance of behavior in mediating the net effects of warming at the population and the individual level using captive white-tailed deer (Odocoileus virginianus). I created thermal heterogeneity over feeding stations using opaque and translucent roofing material. Feeding activity and consumption were monitored at these feeders. Activity patterns revealed deer disproportionally used the shaded feeder during the daytime and the unshaded feeder during crepuscular periods. I found that deer consumed less feed in group and individual experiments when feeders were unshaded. My results suggest that deer can use heterogeneity in the environment that may mediate the net effects of climate change. Furthermore, maintaining thermal heterogeneity may mitigate the direct effects of climate change on the consumer, but may lead to indirect effects at the community level.

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This study reports the results of different staining techniques on the chromosomes of two Poecilia formosa lineages, providing evidence of two additional nucleolus organizer region (NOR) chromosomal clones in this gynogenetic fish. A comparative analysis of chromosomal clones detected in the Amazon molly, along with their frequency and distribution in different collecting sites, is also presented, and clonal heterogeneity resulting from chromosome changes is discussed.

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Cyclic di-GMP is a second messenger used by bacteria to regulate motility, extracellular polysaccharide production, and the cell cycle. Recent advances in the measurement of real time cyclic di-GMP levels in single cells have uncovered significant dynamic heterogeneity of second messenger concentrations within bacterial populations. This heterogeneity results in a wide range of phenotypic outcomes within a single population, providing the potential for population survival and adaptability in response to rapidly changing environments. In this chapter, we discuss some of the measurement technologies available for single-cell measurement of cyclic di-GMP concentrations, the resulting discovery of heterogeneous cyclic di-GMP populations, the mechanisms bacteria use to generate this heterogeneity, and the biochemical and functional consequences of heterogeneity on cyclic di-GMP effector binding and the bacterial population.

When testing for the equality of regression slopes based on ordinary least squares (OLS) estimation, extant research has shown that the standard F performs poorly when the critical assumption of homoscedasticity is violated, resulting in increased Type I error rates and reduced statistical power (Box, 1954; DeShon & Alexander, 1996; Wilcox, 1997). Overton (2001) recommended weighted least squares estimation, demonstrating that it outperformed OLS and performed comparably to various statistical approximations. However, Overton's method was limited to two groups. In this study, a generalization of Overton's method is described. Then, using a Monte Carlo simulation, its performance was compared to three alternative weight estimators and three other methods. The results suggest that the generalization provides power levels comparable to the other methods without sacrificing control of Type I error rates. Moreover, in contrast to the statistical approximations, the generalization (a) is computationally simple, (b) can be conducted in commonly available statistical software, and (c) permits post hoc analyses. Various unique findings are discussed. In addition, implications for theory and practice in psychology and future research directions are discussed.