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Evolution In Changing Environments

Author: Richard Levins
Publisher: Princeton University Press
ISBN: 9780691080628
Size: 75.24 MB
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On theories and models. Strategies of adaptation. The theory of the niche. The species in space. The genetic system. From micro to macro evolution.

Evolution In Changing Environments

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The relative contribution of various evolutionary mechanisms to the maintenance of genetic polymorphism in nature is still unclear. Temporally varying selection is thought to typically act to reduce diversity in nature, while it could act to protect polymorphism under heterozygous advantage across environments, in the presence of seed banks, or under density-dependent regulation. This thesis explores the effects of predictably changing environments on levels of non-neutral polymorphism (1) using a novel model of cyclic selection, (2) expanding its settings to include spatial heterogeneity in the magnitude of cyclic selection, and (3) by accounting for the effects of phenotypic plasticity. (1) I show that in an isolated population, cyclic selection when weak or of short period is unlikely to reduce or elevate the expected diversity at a selected locus, while strong cyclic selection of long periods typically acts to reduce diversity when derived allele is on average as fit or fitter than ancestral allele and to moderately increase diversity when derived allele is less fit than ancestral allele. (2) However, cyclic selection of spatial heterogeneous magnitude can lead to long-term maintenance of diversity. This effect increases with population size and is generally robust to unequal average fitnesses of two alleles. This effect dissipates as magnitudes of cyclic selection in subpopulations become equal. (3) Additionally, the joint effects of phenotypic plasticity via a modifier locus and of cyclic selection can lead to long-term maintenance of variation at both a plasticity modifier and a target locus. I propose that cyclic selection can lead to maintenance of genetic polymorphism at the non-neutral locus under larger set of conditions than previously thought. I suggest that cyclic environments could be a precursor to rapid adaptation from standing genetic variation.

Evolutionary Dynamics In Changing Environments

Author: Frank Stollmeier
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Evolution can be understood as an optimization mechanism on the fitness function, which is defined as the reproductive success of a species. If the environmental conditions remain constant, the stationary states of the evolutionary dynamics are the phenotypes at the local maxima of the fitness function. However, a more realistic assumption is that the environmental conditions permanently change on several timescales. The temperature, for example, typically changes between day and night, between summer and winter, and due to short-term weather changes and long-term climate changes. Since the...

The Evolution Of Genetic And Epigenetic Diversity In Changing Environments

Author: Oana Carja
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The production and maintenance of genetic and phenotypic diversity under temporally fluctuating selection has been a major focus of study in population genetics for more than five decades. In this thesis, I use analytical and computational models to gain insight into the relative roles of genetic and epigenetic diversity in adaptation to changing selection. The different chapters provide complimentary perspectives on the signatures of environmental volatility in the patterns of variation. Chapter 2 explores the evolution of epigenetic variation and its role in adaptation under changing selection pressures. Chapter 3 investigates the effect of recombination on the geometric mean principle under different environmental regimens and fitness landscapes. Two chapters of this thesis, Chapter 4 and Chapter 5 explore the evolution of phenotypic switching, a phenomenon widely documented in viruses, yeast and bacteria, where offspring can express a phenotype different from those of their parents. These chapters highlight the interplay of spatial and temporal environmental variability, offering new insights into how migration can influence the evolution of stochastic switching rates, epigenetic inheritance, and sources of phenotypic variation. Chapter 6 compares and contrasts how fluctuating selection shapes the rates of recombination, mutation and migration, highlighting surprising similarities in their evolutionary dynamics to changing selection. This chapter offers new insights into the role of the environmental duration, shape and randomness in predicting the long-term evolutionary advantage of the forces of recombination, mutation and migration. The models and analyses presented here provide a more complete understanding of the role of genetic and epigenetic diversity in adaptation to changing selection pressures.

Environment Development And Evolution

Author: Katrin Schäfer
Publisher: MIT Press
ISBN: 9780262083195
Size: 33.84 MB
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Leading researchers in evolutionary developmental biology seek linkages between, and a synthesis of, development, physiology, endocrinology, ecology, and evolution. Evolutionary developmental biology, also known as evo-devo or EDB, seeks to find links between development and evolution by opening the "black box" of development's role in evolution and in the evolution of developmental mechanisms. In particular, this volume emphasizes the roles of the environment and of hormonal signaling in evo-devo. It brings together a group of leading researchers to analyze the dynamic interaction of environmental factors with developmental and physiological processes and to examine how environmental signals are translated into phenotypic change, from the molecular and cellular level to organisms and groups of organisms. Taken together, these chapters demonstrate the crucial roles of those processes of genetic, developmental, physiological, and hormonal change that underpin evolutionary change in development, morphology, physiology, behavior, and life-history. Part I investigates links between environmental signals and developmental processes that could be preserved over evolutionary time. Several contributors evaluate the work of the late Ryuichi Matsuda, especially his emphasis on the role of the external environment in genetic change and variability ("pan-environmentalism"). Other contributors in part I analyze different aspects of environmental-genetic-evolutionary linkages, including the importance of alternate ontogenies in evolution and the paradox of stability over long periods of evolutionary time. Part II examines the plasticity that characterizes much of development, with contributors discussing such topics as gene regulatory networks and heterochronicity. Part III analyzes the role of hormones and metamorphosis in the evolution of such organisms with alternate life-history stages as lampreys, amphibians, and insects.

Adaptation And Evolution In Marine Environments Volume 1

Author: Guido di Prisco
Publisher: Springer Science & Business Media
ISBN: 3642273521
Size: 35.23 MB
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The poles undergo climate changes exceeding those in the rest of the world in terms of their speed and extent, and have a key role in modulating the climate of the Earth. Ecosystems adapted to polar environments are likely to become vulnerable to climate changes. Their responses allow us to analyse and foresee the impact of changes at lower latitudes. We need to increase our knowledge of the polar marine fauna of continental shelves, slopes and deep sea, as identifying the responses of species and communities is crucial to establishing efficient strategies against threats to biodiversity, using international and cross-disciplinary approaches. The IPY 2007-2009 was a scientific milestone. The outstanding contribution of Marine Biology is reflected in this volume and the next one on “Adaptation and Evolution in Marine Environments – The Impacts of Global Change on Biodiversity” from the series “From Pole to Pole”, making these volumes a unique and invaluable component of the scientific outcome of the IPY.

Adaptation And Evolution In Marine Environments Volume 2

Author: Cinzia Verde
Publisher: Springer Science & Business Media
ISBN: 3642273491
Size: 27.62 MB
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The second volume of “Adaptation and Evolution in Marine Environments – The Impacts of Global Change on Biodiversity” from the series “From Pole to Pole” integrates the marine biology contribution of the first tome to the IPY 2007-2009, presenting overviews of organisms (from bacteria and ciliates to higher vertebrates) thriving on polar continental shelves, slopes and deep sea. The speed and extent of warming in the Arctic and in regions of Antarctica (the Peninsula, at the present ) are greater than elsewhere. Changes impact several parameters, in particular the extent of sea ice; organisms, ecosystems and communities that became finely adapted to increasing cold in the course of millions of years are now becoming vulnerable, and biodiversity is threatened. Investigating evolutionary adaptations helps to foresee the impact of changes in temperate areas, highlighting the invaluable contribution of polar marine research to present and future outcomes of the IPY in the Earth system scenario.


Author: Carla Mooney
Publisher: Build It Yourself
ISBN: 9781619306011
Size: 72.80 MB
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Introduces the concept of biological evolution, explaining how minute changes over time lead to speciation, in a book that includes twenty-five science projects that illustrate key concepts.