Genetic Accomodation, Assimilation, and Adaptive Evolution Across Thermal Environments in Drosophila Melanogaster PDF Download
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Author: Kendall Mills
Publisher:
ISBN:
Category : Drosophila melanogaster
Languages : en
Pages : 44
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Author: Kendall Mills
Publisher:
ISBN:
Category : Drosophila melanogaster
Languages : en
Pages : 44
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Author: Lindsey Caroline Fallis
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Temperature is a critical environmental parameter and thermal variation has significant effects on local adaptation and species distributions in nature. This is especially true for organisms that are isothermal with their environment. Variation in temperature imposes stress and directly influences physiology, behavior, and fitness. Thus, to thrive across a range of thermal environments populations must contain sufficient genetic variation, the capacity to respond plastically, or some combination of both genetic and plastic responses. In this work I first quantified patterns of phenotypic and genetic variation in nature and then dissected the genetic basis of variation in thermal traits. In the first aim I used natural populations of Drosophila melanogaster collected from a latitudinal transect in Argentina to investigate variation in heat stress resistance and cold plasticity within and among populations. I found heat stress resistance was highly variable within populations, but was strongly associated with the monthly maximum average temperature of each site. For cold plasticity I was able to demonstrate significant variation in plasticity within and among populations, however the among population variation was best explained by the altitude of each site. I hypothesized that this was caused by a difference in temperature fluctuations at high altitude sites relative to low altitude sites. To evaluate this hypothesis I paired our study with existing laboratory data that demonstrated significant fitness differences between high and low plasticity (and altitude) sites when these populations were reared in variable thermal environments. Thus, cold plasticity is an adaptive response to environmental variation. The final project focused on understanding the genetic basis of thermal variation. I fine-mapped a single co-localized heat and cold tolerance QTL via deficiency and mutant complementation mapping to identify four novel thermal candidate genes. There was no overlap of the deficiencies or genes associated with cold or heat stress resistance. Sequence analysis of each gene identified the polymorphisms that differentiate the lines. To test for independent associations between these polymorphisms and variation in nature the Drosophila Genome Reference Panel was used to confirm associations between allelic variation and cold tolerance in nature.
Author: William Andrew Russey
Publisher:
ISBN:
Category : Biology
Languages : en
Pages :
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Variation in morphology results in variation in ecologically relevant performances, which ultimately results in variation in fitness allowing for adaptive evolution. Task performances, such as flight ability, result from the proper scaling of and functional integration of numerous component traits. Morphological variation underlying ecologically relevant task performances can experience strong environmental effects in their expression, or phenotypic plasticity. Historically, the role phenotypic plasticity in adaptive evolution has been controversial, although it has garnered increased support in recent decades. Drosophila spp. are globally distributed and exhibit convergent morphological clines in flight morphology, and importantly, they also exhibit patterns of phenotypic plasticity consistent with these geographic patterns. In the work presented here, I examine if existing patterns of D. melanogaster flight morphology are adaptive regarding flight performance and fitness under the prediction of phenotype-environment matching, wherein the phenotype expressed in an environment enhances fitness in the predicted environment. In the work presented here, I demonstrate (i) phenotypic plasticity in D. melanogaster exhibits a pattern of adaptive phenotype-environment matching in which an induced phenotype is best-suited for flight at the temperature of development, (ii) the pattern of thermally-induced phenotypic plasticity facilitates the evolution of upwind flight performance at Cool and Warm flight temperatures, (iii) adaptive evolution by genetic accommodation is a dynamic process and the contribution of traits responding to selection vary and change over time, and finally, (iv) the adaptive pattern of phenotype-environment matching regarding flight performance is only partially realized as an increase to fitness, measured as survival in presence of predators. My dissertation work importantly demonstrates existing patterns of phenotype-environment matching in D. melanogaster, and demonstrates how this pattern facilitates adaptive evolution by genetic accommodation in a complex phenotype that exhibits natural, continuous variation.
Author: Philip John Freda
Publisher:
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Category :
Languages : en
Pages :
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Complex life cycles (CLCs), developmental programs in which life-history stages are distinct in morphology, behavior, and physiology, are common throughout the biosphere. However, it is still unclear why and how CLCs evolve. The adaptive decoupling hypothesis (ADH) postulates that CLCs evolve to decouple the developmental processes that underlie traits across ontogeny to allow for independent, stage-specific responses to selection. This ultimately could lead to alternate life-history stages adapting to unique environments, thus optimizing fitness across development. However, few empirical tests of the ADH are available. Detecting genetic and transcriptomic decoupling of thermal hardiness using robust techniques in a model system, D. melanogaster, was the goal of this dissertation. Furthermore, this work illustrates that different life-history stages have the potential to become adapted to unique ecological niches. I performed three primary studies to test the ADH: 1.) estimation of the genetic correlation for cold hardiness between larvae and adults using isogenic lines of D. melanogaster to determine if unique genetic architectures underlie variation in cold stress response using standard quantitative genetic and Genome-Wide Association (GWA) methods, 2.) testing whether developmental acclimation is genetically correlated across stages, and whether acclimation alters cross-stage correlations in cold hardiness, and 3.) analysis of the transcriptional responses of both larvae and adults to extreme cold to determine if stage-specific stress response mechanisms exist across development.
Author: Susanne Voigt
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Emily Louise Behrman
Publisher:
ISBN:
Category :
Languages : en
Pages : 424
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The rate and tempo at which populations respond to environmental change is fundamental in understanding the adaptive process. Evolution is generally considered to be a gradual process and it is unclear if populations can adapt rapidly to environmental selection pressures. Annual seasonal rhythms produce rapid, predictable environmental changes that may result in rapid adaptation in multivoltine species that reproduce multiple times each year. This work demonstrates that Drosophila melanogaster adapts rapidly and predictably to seasonal environmental changes across five years and multiple locations. Suites of complex fitness traits change in a predictable way over the 10-15 generations from spring to fall. After surviving the harsh environmental selection of the winter, the spring flies are characterized by a increased investment in somatic maintainance: higher resistance to thermal stress, higher tolerance to pathogenic infection, faster development time and better learning. These traits decline throughout the summer when ripening fruit is abundant due to correlated trade-offs with reproduction. Parallel changes in G-matrixes over this seasonal timescale counters the basic assumption of stable covariance over time and indicates that selection acts rapidly to alter the genetic architecture of a population. We show that there are alleles that have functional effects on these important life history traits that oscillate in frequency as a function of seasonal time, but that non-additive epistatic interactions are prevalent and shape the genetic architecture of change across seasonal time. Functional analysis of candidate genes shows that epistatic interactions among seasonally oscillating alleles facilitate rapid adaptation by producing emergent fitness phenotypes. Together, these findings demonstrate rapid, repeatable adaptation to abiotic and biotic environmental parameters that cycle as a function of seasonal time. Epistatic interactions within and among genes facilitate the rapid evolutionary change that is occurring over timescales previously considered static.
Author: Fiona Elizabeth Cockerell
Publisher:
ISBN:
Category :
Languages : en
Pages : 298
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Book Description
Since heat stress affects most organisms it is important that we understand how adaptation occurs to increasingly warm environment, especially the underlying changes in physiology, biochemistry and genetics. Few studies have shown links between physiological mechanisms and heat tolerance phenotypes in an adaptive context. Therefore the overall aim of this thesis was to use the model organism Drosophila melanogaster to elucidate the role of two heat-tolerance candidate genes hsr-omega and hsp90 in thermal adaptation, and to look at this in a physiological context which included examining rates of protein synthesis, a postulated underlying process.Using geographically diverse populations of D. melanogaster from eastern Australia I found that heat tolerance is a plastic trait that depends on rearing temperature and heat-stimulus conditions, and that the adaptive latitudinal clines in heat tolerance depend on these rearing conditions. Protein synthesis rate showed latitudinal clines that also depend on both the temperature at which flies are reared (18 or 25 °C) and heat-stress conditions (either unstressed (basal) or following a 37 °C heat stimulus), and these clines ran in parallel to clines in heat knockdown tolerance, although no evidence that the clines are connected was obtained. Consistent negative correlations between variation in protein synthesis rate and heat knockdown tolerance in a derived North/South hybrid population confirmed the importance of protein synthesis rate as a factor underlying heat tolerance variation within populations. However the latitudinal cline in protein synthesis did not help explain the latitudinal heat tolerance variation as this would require a positive association between the two variables. A gene thought to help control rates of general protein synthesis following heat stimulus, hsr-omega, was investigated for changes in expression across latitude. Clines in basal and heat-stimulated omega-n transcript level suggest that there is adaptive genetic differentiation in hsr-omega expression between populations from different climatic regions. I show for the first time evidence for a link between expression of another heat shock gene, hsp90, and adult heat knockdown tolerance. Tissue levels of hsp90 transcript and protein were negatively associated with tolerance in several independent data sets. Further, this negative association extended to a set of populations from different thermal niches and revealed a positive linear latitudinal cline for both basal hsp90 transcript and protein level. These data suggest that heritable variation in hsp90 expression contributes to traits that facilitate adaptation to different climatic regions, including the clinal variation in thermal tolerance. I also discuss a plausible causal role for hsp90 as a negative regulator of the cellular heat shock response that predicts the above negative hsp90-tolerance association, particularly the interaction between Hsp90 protein and Heat shock factor.Overall these data make a significant contribution to understanding the process of adaption to divergent thermal habitats and to the cellular processes and genes that facilitate thermal adaptation.
Author: Michael J. Angilletta Jr.
Publisher: Oxford University Press
ISBN: 0191547204
Category : Science
Languages : en
Pages :
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Book Description
Temperature profoundly impacts both the phenotypes and distributions of organisms. These thermal effects exert strong selective pressures on behaviour, physiology and life history when environmental temperatures vary over space and time. Despite temperature's significance, progress toward a quantitative theory of thermal adaptation has lagged behind empirical descriptions of patterns and processes. In this book, the author draws on theory from the more general discipline of evolutionary ecology to establish a framework for interpreting empirical studies of thermal biology. This novel synthesis of theoretical and empirical work generates new insights about the process of thermal adaptation and points the way towards a more general theory. The threat of rapid climatic change on a global scale provides a stark reminder of the challenges that remain for thermal biologists and adds a sense of urgency to this book's mission. Thermal Adaptation will benefit anyone who seeks to understand the relationship between environmental variation and phenotypic evolution. The book focuses on quantitative evolutionary models at the individual, population and community levels, and successfully integrates this theory with modern empirical approaches. By providing a synthetic overview of evolutionary thermal biology, this accessible text will appeal to both graduate students and established researchers in the fields of comparative, ecological, and evolutionary physiology. It will also interest the broader audience of professional ecologists and evolutionary biologists who require a comprehensive review of this topic, as well as those researchers working on the applied problems of regional and global climate change.
Author: Don Rittner
Publisher: Infobase Publishing
ISBN: 1438109997
Category : Biology
Languages : en
Pages : 417
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Book Description
Contains approximately 800 alphabetical entries, prose essays on important topics, line illustrations, and black-and-white photographs.
Author: Carl Schlichting
Publisher: Sinauer Associates Incorporated
ISBN: 9780878937998
Category : Science
Languages : en
Pages : 387
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Book Description
Phenotypic expression has variously been attributed to developmental, genetic and environmental factors. This book presents a cohesive view of how adaptive phenotypes evolve, recognizing organisms as complex genetic-epigenetic systems that develop in response to changing environments.
