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Genetic Disequilibria and the Interpretation of Population Genetic Structure in Daphnia
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology.
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Understanding the processes that shape the spatial distribution of genetic variation within species is central to the evolutionary study of diversification and demography. Neutral genetic variation reflects past demographic events as well as current demographic characteristics of populations, and the correct interpretation of genetic data requires that the relative impact of these forces can be identified. Details of breeding systems can affect the genetic structure through effects on effective migration rate or on effective population size. Restrictions in recombination rate lead to associations between neutral marker genes and genes under natural selection. Although the effects on genetic structure can be substantial, the process will often be difficult to tell apart from stochastic effects of history or genetic drift, which may suggest erroneous conclusions about demography.

In cyclically parthenogenetic freshwater invertebrates, which alternate between sexual and asexual reproduction, demographic fluctuations and reliance on diapausing eggs for dispersal enhances neutral genetic differentiation as well as effects of selection on associated genes. Although genetic founder effects are expected to be profound and long-lasting in these species, genetic hitch-hiking may reduce initial strong differentiation rapidly if better adapted genes are introduced by mutation or immigration. Fluctuating environmental conditions have been suggested to generate rapid shifts in the frequencies of clones during the asexual phase. In the presence of egg banks resting in sediments, genetic diversity is stabilised and the importance of migration for differentiation is reduced.

Studies of unstable and young populations of cyclically parthenogenetic Daphnia pulex showed substantial variation for important fitness traits, within as well as between populations, despite hypothesised recent founder effects. Neutral markers indicated genetic equilibrium, but changes in clonal composition during asexuality disrupted the genetic structure in a manner compatible with local adaptation and exclusion of immigrants. This illustrates that the forces affecting sexual progeny may be markedly different from those shaping the structure among asexual individuals.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2001. , p. 36
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 668
Keywords [en]
Developmental biology, breeding system, linkage disequilibrium, dispersal, genetic structure, Daphnia pulex
Keywords [sv]
Utvecklingsbiologi
National Category
Developmental Biology
Research subject
Conservation Biology
Identifiers
URN: urn:nbn:se:uu:diva-1498ISBN: 91-554-5152-7 (print)OAI: oai:DiVA.org:uu-1498DiVA, id: diva2:161073
Public defence
2001-11-29, Friessalen, Evolutionary Biology Centre, Villavägen 9, 752 36 Uppsala, Uppsala, 10:00
Opponent
Available from: 2001-11-07 Created: 2001-11-07Bibliographically approved

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