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Visar resultat 1 - 5 av 20 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Genetic variation in structured populations

    Författare :Marina Rafajlovic; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; genetic variation; varying population size; effective population size; mutation; recombination; migration; multiple paternity; geographic structure; tests of neutrality; gene tree; species tree;

    Sammanfattning : It is widely acknowledged that the process of speciation in the presence of gene flow between different ecotypes is common in nature. However, the mechanisms underlying speciation are not understood. LÄS MER

  3. 2. Inbreeding, Effective Population Sizes and Genetic Differentiation : A Mathematical Analysis of Structured Populations

    Författare :Fredrik Olsson; Ola Hössjer; Steinar Engen; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; matematisk statistik; Mathematical Statistics;

    Sammanfattning : This thesis consists of four papers on various aspects of inbreeding, effective population sizes and genetic differentiation in structured populations, that is, populations that consist of a number of subpopulations. Three of the papers concern age structured populations, where in the first paper we concentrate on calculating the variance effective population size (NeV) and how NeV depends on the time between measurements and the weighting scheme of age classes. LÄS MER

  4. 3. Alternative Stable States in Size-Structured Communities : Patterns, Processes, and Mechanisms

    Författare :Arne Schröder; Lennart Persson; André M. de Roos; Tim Benton; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; biomass overcompensation; Chaoborus; emergent Allee effect; Heterandria formosa; juvenile recruitment bottlenecks; ontogenetic niche shifts; Poecilia reticulata; Biology; Biologi;

    Sammanfattning : Alternative stable states have been, based on theoretical findings, predicted to be common in ecological systems. Empirical data from a number of laboratory and natural studies strongly suggest that alternative stable states also occur in real populations, communities and ecosystems. LÄS MER

  5. 4. Invasion of top and intermediate consumers in a size structured fish community

    Författare :Per Ask; Lennart Persson; Daniel E Schindler; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Invasion; intraguild predation; size-structure; cannibalism; climate; temperature; Arctic char; ninespine stickleback; Freshwater ecology; Limnisk ekologi; biology; biologi;

    Sammanfattning : In this thesis I have investigated the effects of invading top and intermediate consumers in a size-structured fish community, using a combination of field studies, a lake invasion experiment and smaller scale pond and aquaria experiments. The lake invasion experiment was based on introductions of an intermediate consumer, ninespine stickleback (Pungitius pungitius L. LÄS MER

  7. 5. Food Web Ecology -- individual life-histories and ecological processes shape complex communities

    Författare :Martin Hartvig; Evolutionär ekologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; food web; community ecology; community assembly; size-structure; life-history omnivory; ontogeny; trophic interactions; trait based model; topology; emergent organisation; size-spectrum;

    Sammanfattning : This thesis sets out a food web framework for size-structured populations. The framework enables an ecological approach to food web modelling as the individual life-history from birth, through maturation, and ultimately death is explicitly resolved with the use of bioenergetics based on individual body size. LÄS MER