Re: sexual selection and memes

From: Chris Taylor (
Date: Tue Jun 19 2001 - 16:35:08 BST

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    Here's a great example of memes exploiting phenotypic plasticity (the
    effect of varying environments on a standard genotype) in the sparrow. I
    don't mention it for any particular reason, I just think it's rather
    interesting because this is meme-to-meme communication via phenotype,
    with a dollop of sexual selection - but for memes not genes.

    Basically, male (UK) sparrows have a 'badge' on their chest (a large
    brown splodge); this is indicative of how well raised they are (i.e. it
    correlates with the degree of parental care, rather than being
    inherited). Females select for large chest patches, because male
    sparrows with such large chest patches are good carers of offspring
    (i.e. make a large parental investment of time and energy rather than
    being the classic deadbeat dad). What this amounts to is 'good memes'
    sexual selection. This is a version of the classic 'good genes' reason
    for sexual selection (my bright orange arse indicates I'm carrying high
    fitness alleles); but in this case, the badge indicates that the
    potential father has experienced extensive paternal care as a young
    bird, and will therefore repeat this learned behaviour when it is itself
    a parent. However apart from the ability to display this phenotypic
    plasticity, no actual genes are being selected for here, even though
    this is undeniably sexual selection.


    Here's the abstract just in case anyone cares...

    Nature 400, 358 - 360 (1999) © Macmillan Publishers Ltd.
    Environmental determination of a sexually selected trait


    Models of sexual selection usually assume that variation in the
    expression of sexual ornaments is determined largely by genetic, rather
    than environmental, factors. However, empirical support for this
    assumption comes from studies of species with little parental care, in
    which the influence of environmental factors may be limited, and from
    studies of just two species, with parental care, in both of which
    heritability estimates vary hugely between years or populations,. In the
    remaining studies of species with parental care, it is not known whether
    resemblance in sexual ornamentation between relatives was due to shared
    genes or shared patterns of care. Here we use cross-fostering
    experiments in house sparrows, Passer domesticus, to examine the
    relative roles of these effects. We demonstrate that, although sons
    resemble their fathers with respect to sexual ornamentation, this
    resemblance is mainly due to post-hatching environmental effects rather
    than shared genes. We also show that sons hatching early in the year
    have the largest ornaments. These results support models that emphasize
    the importance of environmental sources of variation, such as direct
    paternal effects, on the expression of sexual ornaments, and agree with
    the general observation that sexually selected traits tend to be
    condition dependent. We urge the incorporation of gene–environment
    interactions into future models of sexual selection.

     Chris Taylor ( »people»chris

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