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  • 1.
    Demandt, Marnie H
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Biodiversity in Swedish Cyprinid Fish: Insights Into Processes of Divergence2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Uncovering and understanding the processes that have led to the biological diversity we observe today are of fundamental interest in biology. Since direct observation of speciation is usually impossible, knowledge about the processes behind species formation can be gathered by studying mutations, natural/sexual selection, and genetic drift. In this thesis I aim to identify evolutionary processes that cause species divergence and, ultimately, speciation using Swedish cyprinid fish as a model system. Assuming that the demographic history of a population is mirrored in the genome, I studied the effects of a bottleneck on genetic variability in populations of roach. As expected, I found that a decrease in population size caused a decrease in genetic variability, a pattern that was obtained from both microsatellite and mitochondrial data. The importance of hybridization for speciation is debated, however, by analyzing morphology and microsatellites I could show that common bream and white bream and their interspecific hybrids are phenotypically and genetically differentiated and that ongoing geneflow is mainly unidirectional. Ongoing geneflow antagonizes the effect of genetic drift, but by studying isolated populations (= no gene flow) the impact of genetic drift can be assessed. Long-term isolated populations of roach and perch surprisingly showed stable levels of genetic diversity over time despite decreasing effective population size. However, each population genetically diverged during the period of investigation, a finding that is consistent with the effect of drift. An analysis of the systematic relationship of the 18 species of Swedish cyprinids revealed low congruence of phylogenies based on two different genetic markers. The position of the tench remains unresolved and the relationship of common bream and white bream as sister species cannot be confirmed. Within cyprinid fishes, diversification rates reveal a slowdown with time, a pattern that I found also in other fish clades and that is consistent with density-dependent cladogenesis. Overall, based on the findings presented in this thesis I emphasize that the maintenance of genetic variation in populations is essential since genetic variation is the key element for processes of divergence to act upon.

    List of papers
    1. Loss of genetic variability in reintroduced roach (Rutilus rutilus) populations
    Open this publication in new window or tab >>Loss of genetic variability in reintroduced roach (Rutilus rutilus) populations
    2007 (English)In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 70, no Suppl.B, p. 255-261Article in journal (Refereed) Published
    Abstract [en]

    Genetic variation at five microsatellite loci and in mtDNA was surveyed in reintroduced and 'control' populations of roach (Rutilus rutilus) in Sweden. Microsatellite allelic richness and allele size ranges were significantly reduced in reintroduced populations, and mtDNA diversity was nearly significantly reduced in reintroduced populations. These measures of genetic variability were strongly correlated with lake characteristics that influence population size and food availability.

    Keywords
    genetic variation, lake acidification, population bottleneck, reintroductions, roach
    National Category
    Biological Sciences
    Identifiers
    urn:nbn:se:uu:diva-108617 (URN)10.1111/j.1095-8649.2007.01408.x (DOI)000246440500009 ()
    Available from: 2009-09-24 Created: 2009-09-24 Last updated: 2017-12-13Bibliographically approved
    2. Identification of cyprinid hybrids by using geometric morphometrics and microsatellites
    Open this publication in new window or tab >>Identification of cyprinid hybrids by using geometric morphometrics and microsatellites
    2009 (English)In: Journal of Applied Ichthyology, ISSN 0175-8659, E-ISSN 1439-0426, Vol. 25, no 6, p. 695-701Article in journal (Refereed) Published
    Abstract [en]

    Traditional morphological studies need to be complemented with modern genetic methods to facilitate the identification of hybrids. By using a combination of landmark-based techniques and microsatellite markers, natural hybridization was investigated between the cyprinids Abramis brama (L.) and Blicca bjoerkna (L.) and their hybrids. Geometric morphometrics revealed significant differences in body shape between A. brama, B. bjoerkna, and hybrids. Hybrids were of intermediate body shape with a tendency of being more like A. brama. Genetic differentiation was found between both parental species and their hybrids. However, hybrids revealed a higher genetical similarity with A. brama. Based on sequencing of the mitochondrial ATP synthase subunit 6 and 8 region a clear split was found between the two sibling species. Seventeen out of 19 hybrid specimens clustered within the A. brama clade. Data indicate that hybridization between A. brama and B. bjoerkna is mainly unidirectional and has not yet resulted in fusion of the two parental gene pools. Genetic integrity is maintained in B. bjoerkna, but F1 hybrid backcrosses might lead to introgression into the genepool of A. brama.

    National Category
    Biological Sciences
    Identifiers
    urn:nbn:se:uu:diva-108993 (URN)10.1111/j.1439-0426.2009.01329.x (DOI)000272379800010 ()
    Available from: 2009-10-06 Created: 2009-10-06 Last updated: 2017-12-13Bibliographically approved
    3. Stable levels of gene diversity despite low effective population size in isolated perch and roach populations
    Open this publication in new window or tab >>Stable levels of gene diversity despite low effective population size in isolated perch and roach populations
    (English)Manuscript (preprint) (Refereed)
    Keywords
    temporal variation, effective population size, genetic diversity, isolation by time, perch, roach
    Identifiers
    urn:nbn:se:uu:diva-108615 (URN)
    Available from: 2009-10-06 Created: 2009-09-24 Last updated: 2010-01-14Bibliographically approved
    4. Phylogenetic relationships in Swedish cyprinid fish: evidence from mitochondrial and nuclear data
    Open this publication in new window or tab >>Phylogenetic relationships in Swedish cyprinid fish: evidence from mitochondrial and nuclear data
    (English)Manuscript (preprint) (Refereed)
    Identifiers
    urn:nbn:se:uu:diva-108996 (URN)
    Available from: 2009-10-06 Created: 2009-10-06 Last updated: 2010-01-14
  • 2.
    Demandt, Marnie H
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Stable levels of gene diversity despite low effective population size in isolated perch and roach populationsManuscript (preprint) (Refereed)
  • 3. Goedkoop, W.
    et al.
    Demandt, Marnie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
    Ahlgren, Gunnel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Interactions between food quantity and quality (long-chain polyunsaturated fatty acid concentrations) effects on growth and development of Chironomus riparius2007In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 64, no 3, p. 425-436Article in journal (Refereed)
    Abstract [en]

    We quantified somatic growth, development, and emergence of the midge Chironomus riparius on experimental diets (oats, Spirulina, and Tetraphyll (R)) covering gradients in food quality (differing polyunsaturated fatty acids) and quantity (0.1-5.4 mg C center dot day(-1)). Additionally, similar incubations without food additions were made using a food-poor sediment containing peat and the green alga Scenedesmus obliquus. Larval and adult size was affected by both food quantity and quality and increased some three to four times across the food concentration gradients. Adult emergence, however, was affected only by food quantity. A type 3 response model showed that a saturation level was reached for the oats treatment at 2.7 mg C center dot day(-1) (or 3.9 mu g omega 3 and 120 mu g omega 6 polyunsaturated fatty acids center dot day(-1)), indicating that the quality of oats constrained further stimulation of larval growth. In the peat treatment, larval growth was very low, no adults emerged, and no larvae even made it to the pupa stage. Fatty acid analyses showed that larvae were capable of synthesizing arachidonic acid via gamma-linolenic acid by Delta 6- and Delta 5-desaturase activity using linoleic acid available in food sources. This strongly suggests that C. riparius is not dependent on dietary sources of eicosapentaenoic acid and arachidonic acid and can sustain viable populations even under a low-quality food regimen.

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