An integrated investigation of the population genetics, physiological stress, and movement patterns in the American pika

The objective of this dissertation was to examine how ecological and micro-evolutionary factors may influence the response of alpine mammals to reductions in habitat quality projected under climate change using the American pika (Ochotona princeps) as a model system. I begin with an overview of anthropogenic impacts on global ecology and ecosystem functioning with an emphasis on the vulnerability of mountain systems to environmental change. I then introduce the American pika and discuss contemporary population loss across the species’ range particularly at the southern end of its distribution in the Great Basin and northeastern California where the regional effects of climate change are expected to increase the co-occurrence of warm and dry conditions over the next few decades. In Chapter 1, I explore the effects of site, season, territory quality (microclimate temperature data) on patterns of physiological stress (via corticosterone stress hormones) in two high-elevation sites in the eastern Sierra Nevada. In Chapter 2, I examine the effects of habitat fragmentation on patterns of long-term pika occupancy as measured by 40 years of census data, and its association with habitat quality (patch perimeter and size), physiological stress, and climate variables calculated from local weather station data for a pika population located at the southern end of the species’ range. In Chapter 3, I track changes in the structure and distribution of genetic variation, effective population size, and movement patterns over the last 65 years within this same vulnerable pika population through the use of historical and contemporary genetic datasets. In Chapter 1, I found that patterns of stress differed significantly among pikas at two sites despite close geographic proximity and that the effects of site, year, territory, and individual diversity on patterns of pika stress were substantial compared to the relatively minor effects of microclimate predictors. In Chapter 2, I discovered significant associations among pika occupancy, temperature patterns, and stress hormone concentrations that suggest a role of individual physiologic response in demographic stability. Finally, in Chapter 3, I provide evidence of genetic erosion and its putative relationship with local climate for a genetically unique pika population at risk of extirpation

<i>CHANDRA</i> OBSERVATIONS OF OUTFLOWS FROM PSR J1509–5850

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VIPP1 rods engulf membranes containing phosphatidylinositol phosphates

In cyanobacteria and plants, VIPP1 plays crucial roles in the biogenesis and repair of thylakoid membrane protein complexes and in coping with chloroplast membrane stress. In chloroplasts, VIPP1 localizes in distinct patterns at or close to envelope and thylakoid membranes. In vitro, VIPP1 forms higher-order oligomers of >1 MDa that organize into rings and rods. However, it remains unknown how VIPP1 oligomerization is related to function. Using time-resolved fluorescence anisotropy and sucrose density gradient centrifugation, we show here that Chlamydomonas reinhardtiiVIPP1 binds strongly to liposomal membranes containing phosphatidylinositol-4-phosphate (PI4P). Cryo-electron tomography reveals that VIPP1 oligomerizes into rods that can engulf liposomal membranes containing PI4P. These findings place VIPP1 into a group of membrane-shaping proteins including epsin and BAR domain proteins. Moreover, they point to a potential role of phosphatidylinositols in directing the shaping of chloroplast membranes

Gallot-Tanno Theorem for closed incomplete pseudo-Riemannian manifolds and applications

We extend the Gallot-Tanno Theorem to closed pseudo-Riemannian manifolds. It is done by showing that if the cone over a manifold admits a parallel symmetric $(0,2)-$tensor then it is Riemannian. Applications of this result to the existence of metrics with distinct Levi-Civita connections but having the same unparametrized geodesics and to the projective Obata conjecture are given. We also apply our result to show that the holonomy group of a closed $(O(p+1,q),S^{p,q})$-manifold does not preserve any nondegenerate splitting of $\R^{p+1,q}$.Comment: minor correction