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Salmo trutta / von Behr vs Loch leven (& male vs felmale).

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  • #16
    Originally posted by jgraham140 View Post
    There are lots of interesting things about the brown trout in the tailwater. They really do resemble Irish Gillaroo from Lough Melvin. Are they descended from Gillaroo or have they converged on a similar phenotype? A genetic analysis would clear that up.

    Phenotypic variation is universal. Quantitative geneticists partition total phenotypic variation of, say, color pattern into several components. There is a genetic component that can be further subdivided into an additive genetic component, a dominance component, and epistasis (gene-gene interaction). Geneticists are usually interested in the additive component because it is the only one of the three that can be inherited. The second component of phenotypic variation is the environmental component. For example, if diet or temperature influence the color pattern, that would be an environmental effect.

    Genes vs environment is sometimes referred to as nature vs nurture in humans, but the principles are the same.

    And then there is an additional component that represents random developmental variation. For example, if the spotting pattern varies between right and left sides of a fish, that would be due to random developmental noise.

    To get at the heritability of color pattern, one would have to do experiments with parents and offspring. If the offspring resemble their parents, the heritability of the trait is probably high. Heritability is usually defined as the ratio of the additive genetic component divided by the total phenotypic variation.

    I have wondered about the gizzard-like stomach in the Gillaroo. How heritable is that trait? Does a Gillaroo require a diet of snails to express the gizzard-like stomach? If it does, then the heritability might be low. There might also be a gene-environment interaction if only the Gillaroo develop a gizzard-like stomach after eating a diet high in snails.

    Finally, how much does diet influence coloration. I can't tell if any of these studies have been done. They may have been, I just haven't had time to find them on Google Scholar.

    Confession: my background is in population genetics, ecological genetics, and evolutionary biology. My main research interests are random developmental noise and hybrid zones (in fish, birds, and sagebrush). I was trained with fish, but have found it easier to work with other species.

    John
    Found a really interesting link that goes even deeper in depth regarding the variety of brown trout found in Ireland. It even mentions that genetic variance is so high amongst brown trout that a geneticist thought that all the trout in Ireland have 5x as much genetic diversity as humans do. Good read and some unreal photos! http://www.angling-ireland.com/brown_trout
    #JBNavy

    "Everyday is a new life to a wise man."
    -Chinese Proverb

    “At sunrise everything is luminous but not clear.”
    -Norman Maclean

    "We are what we hunt."
    -PH

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    • #17
      Originally posted by Philhutch80 View Post
      Found a really interesting link that goes even deeper in depth regarding the variety of brown trout found in Ireland. It even mentions that genetic variance is so high amongst brown trout that a geneticist thought that all the trout in Ireland have 5x as much genetic diversity as humans do. Good read and some unreal photos! http://www.angling-ireland.com/brown_trout
      Nice article. Thanks.

      It isn't unusual that trout have more genetic variation than humans. First, they are partial polyploids, so they have twice as many chromosomes as diploids. And we have relatively little genetic variation compared with other vertebrates. The presumed cause of low human genetic variation is a genetic bottleneck 70,000 years ago caused by the eruption of the Toba super-volcano. The Toba Hypothesis, though, is controversial as the cause of the bottleneck. All we know is that the human population decreased to just a few thousand individuals. This is based on sequence patterns in the DNA.

      John

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