Is Rapid Adaptation to New Environments Fueled by Old Mutations? A Case Study of Copper Tolerance on Mimulus guttatus

Rapid adaptation and tolerance is a phenomenon experienced by a variety of organisms typically because of new and harsh environments. Mimulus guttatus, a plant commonly seen on the west coast of the United States, is a prime example as it has rapidly evolved to soil contamination by copper due to mining in California in the last 150 years. There have been two hypotheses posed by researchers as to the genetic basis of how organisms have evolved so quickly which I set out to study: 1) There is a low frequency of tolerant genotypes in the ancestral population otherwise known as standing variation or 2) new mutations occurred once exposed to a new environment. In the past, researchers found it difficult to distinguish between the two because they lacked the technology we have today for DNA analysis. I used four different populations of M. guttatus from varying locations in order to address which hypothesis was valid. I conducted both survival assays of these populations and DNA analysis of known tolerant and non-tolerant lines using a copper oxidase gene. I found that there was at least some degree of tolerance in all populations in the survival assays, supporting the hypothesis of standing variation. I also found patterns within DNA analysis suggesting the copper oxidase gene would be useful for further study to verify the standing variation hypothesis. The results from this experiment helps in understanding rapid evolution not just in the context of soil contamination by metals but also ties back to why an alarming number of species are not able to adapt to our constantly changing world.

Predicting Forest Responses to Changing Environmental Conditions

Forests change with changes in their environment based on the physiological responses of individual trees. These short-term reactions have cumulative impacts on long-term demographic performance. For a tree in a forest community, success depends on biomass growth to capture above- and belowground resources and reproductive output to establish future generations. Here we examine aspects of how forests respond to changes in moisture and light availability and how these responses are related to tree demography and physiology.

First we address the long-term pattern of tree decline before death and its connection with drought. Increasing drought stress and chronic morbidity could have pervasive impacts on forest composition in many regions. We use long-term, whole-stand inventory data from southeastern U.S. forests to show that trees exposed to drought experience multiyear declines in growth prior to mortality. Following a severe, multiyear drought, 72% of trees that did not recover their pre-drought growth rates died within 10 years. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought-induced morbidity varied among species and was correlated with species drought tolerance.

Next, we investigate differences among tree species in reproductive output relative to biomass growth with changes in light availability. Previous studies reach conflicting conclusions about the constraints on reproductive allocation relative to growth and how they vary through time, across species, and between environments. We test the hypothesis that canopy exposure to light, a critical resource, limits reproductive allocation by comparing long-term relationships between reproduction and growth for trees from 21 species in forests throughout the southeastern U.S. We found that species had divergent responses to light availability, with shade-intolerant species experiencing an alleviation of trade-offs between growth and reproduction at high light. Shade-tolerant species showed no changes in reproductive output across light environments.

Given that the above patterns depend on the maintenance of transpiration, we next developed an approach for predicting whole-tree water use from sap flux observations. Accurately scaling these observations to tree- or stand-levels requires accounting for variation in sap flux between wood types and with depth into the tree. We compared different models with sap flux data to test the hypotheses that radial sap flux profiles differ by wood type and tree size. We show that radial variation in sap flux is dependent on wood type but independent of tree size for a range of temperate trees. The best-fitting model predicted out-of-sample sap flux observations and independent estimates of sapwood area with small errors, suggesting robustness in new settings. We outline a method for predicting whole-tree water use with this model and include computer code for simple implementation in other studies.

Finally, we estimated tree water balances during drought with a statistical time-series analysis. Moisture limitation in forest stands comes predominantly from water use by the trees themselves, a drought-stand feedback. We show that drought impacts on tree fitness and forest composition can be predicted by tracking the moisture reservoir available to each tree in a mass balance. We apply this model to multiple seasonal droughts in a temperate forest with measurements of tree water use to demonstrate how species and size differences modulate moisture availability across landscapes. As trees deplete their soil moisture reservoir during droughts, a transpiration deficit develops, leading to reduced biomass growth and reproductive output.

This dissertation draws connections between the physiological condition of individual trees and their behavior in crowded, diverse, and continually-changing forest stands. The analyses take advantage of growing data sets on both the physiology and demography of trees as well as novel statistical techniques that allow us to link these observations to realistic quantitative models. The results can be used to scale up tree measurements to entire stands and address questions about the future composition of forests and the land’s balance of water and carbon.

Changing epidemiology of serious bacterial infections in febrile infants without localizing signs.

OBJECTIVE: Historically, management of infants with fever without localizing signs (FWLS) has generated much controversy, with attempts to risk stratify based on several criteria. Advances in medical practice may have altered the epidemiology of serious bacterial infections (SBIs) in this population. We conducted this study to test the hypothesis that the rate of SBIs in this patient population has changed over time. PATIENTS AND METHODS: We performed a retrospective review of all infants meeting FWLS criteria at our institution from 1997-2006. We examined all clinical and outcome data and performed statistical analysis of SBI rates and ampicillin resistance rates. RESULTS: 668 infants met criteria for FWLS. The overall rate of SBIs was 10.8%, with a significant increase from 2002-2006 (52/361, 14.4%) compared to 1997-2001 (20/307, 6.5%) (p = 0.001). This increase was driven by an increase in E. coli urinary tract infections (UTI), particularly in older infants (31-90 days). CONCLUSIONS: We observed a significant increase in E. coli UTI among FWLS infants with high rates of ampicillin resistance. The reasons are likely to be multifactorial, but the results themselves emphasize the need to examine urine in all febrile infants <90 days and consider local resistance patterns when choosing empiric antibiotics.

Changing American Congregations: Findings from the Third Wave of the National Congregations Study

The third wave of the National Congregations Study (NCS-III) was conducted in 2012. The 2012 General Social Survey asked respondents who attend religious services to name their religious congregation, producing a nationally representative cross-section of congregations from across the religious spectrum. Data about these congregations was collected via a 50-minute interview with one key informant from 1,331 congregations. Information was gathered about multiple aspects of congregations’ social composition, structure, activities, and programming. Approximately two-thirds of the NCS-III questionnaire replicates items from 1998 or 2006-07 NCS waves. Each congregation was geocoded, and selected data from the 2010 United States census or American Community Survey have been appended. We describe NCS-III methodology and use the cumulative NCS dataset (containing 4,071 cases) to describe five trends: more ethnic diversity, greater acceptance of gays and lesbians, increasingly informal worship styles, declining size (but not from the perspective of the average attendee), and declining denominational affiliation.

Exploring the effects of image persistence in low frame rate virtual environments

© 2015 IEEE.In virtual reality applications, there is an aim to provide real time graphics which run at high refresh rates. However, there are many situations in which this is not possible due to simulation or rendering issues. When running at low frame rates, several aspects of the user experience are affected. For example, each frame is displayed for an extended period of time, causing a high persistence image artifact. The effect of this artifact is that movement may lose continuity, and the image jumps from one frame to another. In this paper, we discuss our initial exploration of the effects of high persistence frames caused by low refresh rates and compare it to high frame rates and to a technique we developed to mitigate the effects of low frame rates. In this technique, the low frame rate simulation images are displayed with low persistence by blanking out the display during the extra time such image would be displayed. In order to isolate the visual effects, we constructed a simulator for low and high persistence displays that does not affect input latency. A controlled user study comparing the three conditions for the tasks of 3D selection and navigation was conducted. Results indicate that the low persistence display technique may not negatively impact user experience or performance as compared to the high persistence case. Directions for future work on the use of low persistence displays for low frame rate situations are discussed.

Economic and social upgrading in global production networks: A new paradigm for a changing world

A key challenge in promoting decent work worldwide is how to improve the position of both firms and workers in value chains and global production networks driven by lead firms. This article develops a framework for analysing the linkages between the economic upgrading of firms and the social upgrading of workers. Drawing on studies which indicate that firm upgrading does not necessarily lead to improvements for workers, with a particular focus on the Moroccan garment industry, it outlines different trajectories and scenarios to provide a better understanding of the relationship between economic and social upgrading. The authors 2011 Journal compilation © International Labour Organization 2011.

NAFTA and uneven development in the North American apparel industry

The various contributions to this book have documented how NAFTA-inspired firm strategies are changing the geography of apparel production in North America. The authors show in myriad ways how companies at different positions along the apparel commodity chain are responding to the new institutional and regulatory environment that NAFTA creates. By making it easier for U.S. companies to take advantage of Mexico as a nearby low-cost site for export-oriented apparel production, NAFTA is deepening the regional division of labor within North America, and this process has consequences for firms and workers in each of the signatory countries. In the introduction to this book we alluded to the obvious implications of shifting investment and trade patterns in the North American apparel industry for employment in the different countries. In this concluding chapter we focus on Mexico in the NAFTA era, specifically the extent to which Mexico's role in the North American economy facilitates or inhibits its economic development. W e begin with a discussion of the contemporary debate about Mexico's development, which turns on the question of how to assess the implications of Mexico's rapid and pro-found process of economic reform. Second, we focus on the textile and apparel industries as sectors that have been significantly affected by changes in regulatory environments at both the global and regional levels. Third, we examine the evidence regarding Mexico's NAFTA-era export dynamism, and in particular we emphasize the importance of interfirm networks, both for making sense of Mexico's meteoric rise among apparel exporters and for evaluating the implications of this dynamism for development. Fourth, we turn to a consideration of the national political-economic environment that shapes developmental outcomes for all Mexicans. Although regional disparities within Mexico are profound, aspects of government policy, such as management of the national currency, and characteristics of the institutional environment, such as industrial relations, have nationwide effects, and critics of NAFTA charge that these factors are contributing to a process of economic and social polarization that is ever more evident (Morales 1999; Dussel Peters 2000). Finally, we suggest that the mixed consequences of Mexico's NAFTA-era growth can be taken as emblematic of the contradictions that the process of globalization poses for economic and social development. The anti-sweatshop campaign in North America is one example of transnational or crossborder movements that are emerging to address the negative consequences of this process. In bringing attention to the problem of sweatshop production in North America, activists are developing strategies that rely on a network logic that is not dissimilar to the approaches reflected in the various chapters of this book. © 2009 by Temple University Press. All rights reserved.