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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Research Effort and Evolutionary Properties of Genes

Struck, Travis Jared, Struck, Travis Jared January 2016 (has links)
Recent research effort (measured in number of publications) on genes is biased towards genes that have been studied heavily in the past. Some factors for why this occurs is that many of these historically studied genes are important for survival or there are more tools available that make genetic studies of them much more accessible. Studies of research effort on \textit{Saccharomyces cerevisiae} genes characterized with genetic or protein interactions found that there is an aversion to studying lesser-known genes in networks. As well, in a study of three human protein families, many of the genes that have recently been discovered to have association with complex disease, through methods such as genome wide association studies (GWAS), are understudied in the present compared to the small number of historically heavily studied genes. In this study we explore possible causes of and diversion from this preferential bias with gene conservation and human genes being disease-associated. We find there is some evidence of conservation driving biases in research effort for essential genes in \textit{Saccharomyces cerevisiae}, but inconclusive evidence in other organisms. We look for effects of disease association through Mendelian and complex diseases in a historical, pre-GWAS, and contemporary, post-GWAS, context. Within both contexts we find that Mendelian disease genes may drive preferential study bias. For contemporary research effort we utilize a model of publication rates and find that there are individual GWAS genes that tend to be investigated more than predicted compared to non-GWAS genes. It appears that the proportion of GWAS genes that had highly unexpected increases in publication rate compared to model predictions rose fairly quickly but has been declining. Our analysis suggests that GWAS has had a small impact on what genes some scientists study despite preferential study biases. However GWAS gene-disease association's impact on research effort appears to be declining, possibly due to scientists not being as interested in GWAS results as time goes on.
2

Understanding Rare Species in California: An Assessment of Camatta Canyon Amole (Hooveria Purpurea Var. Reducta) and a Meta-Analysis of California Rare Plants in Literature

Althaus, Kieran N, , 01 June 2022 (has links) (PDF)
California is currently in the midst of a biodiversity crisis. There are approximately 5,000 native species of plants in California, a quarter of which are considered rare. Determining threats to these rare plants is often times difficult. Despite California's botanical resources, we still know very little about much of California’s rare plants. San Luis Obispo County is home to 2,000 of California’s native plant taxa, one- third of which are rare or endemic to the county. These species are of great local and environmental concern. In Chapter 1, we attempted to assess the impact of non native species on a threatened species in eastern San Luis Obispo County. We conducted an invasive thatch removal experiment on 10 vegetation plots of Camatta Canyon Amole, Hooveria purpurea var. reducta. The Camatta Canyon Amole (CCA) is a federally listed “threatened” plant that is only known to occur on 21.15 ha of land on Los Padres National Forest (LPNF). In the 1980s, U.S. Fish and Wildlife Service established 10 plots to monitor the population of CCA. These biologists recorded a decrease in the CCA since the establishment of those plots in the 1980s. One hypothesis for the decline is the absence of cattle grazing from LPNF, which has resulted in the accumulation of a dense thatch layer. We experimentally removed this thatch layer in five of the 1980s vegetation plots to test this hypothesis. While our the experiment was designed to be a long term treatment, from the first 1.5 years, we found no relationship between thatch removal and the amount of CCA in each plot. The effect of our treatment may take many years to materialize. In Chapter 2, we conducted extensive botanical surveys of the Camatta Ranch, a 32,000 acre cattle ranch in eastern San Luis Obispo County. The goal of these surveys was to estimate the distribution and population size of CCA on private property, which has never before been accessed or surveyed. We did this in two ways: 1) We created a density ratio estimate based off of plot sampling done on the ranch and 2) we created a species distribution model (SDM) to predict the likelihood of presence throughout the ranch. Our surveys of Camatta Ranch, coupled with our SDM suggest that a majority of CCA’s preferred habitat is on Camatta Ranch, making the ranch of paramount concern for CCA’s protection. Our estimates suggest that 90% of the total population of CCA occurs on Camatta Ranch. In Chapter 3, we attempted to quantify biases in the literature about California’s flora. The California Floristic Province is one of the most biologically diverse floras in the world. Considerable legal and conservation attention is given to rare plants in California. However, there is no information as to the research effort given to rare species in California. Here we ask the question: Is there more research done on rare plants in California than on non-rare species? To answer this question, we quantified the amount of literature available on Google Scholar for California’s rare plants, weeds, and non-rare natives. To account for the differences in species geographic extent, we aggregated occurrence data for each species from GBIF to determine their ranges. We found that rare species were severely under-represented in the literature, even after accounting for the differences in species extent.

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