Received: by alpheratz.cpm.aca.mmu.ac.uk id QAA04708 (8.6.9/5.3[ref pg@gmsl.co.uk] for cpm.aca.mmu.ac.uk from fmb-majordomo@mmu.ac.uk); Tue, 19 Jun 2001 16:38:20 +0100 Message-ID: <3B2F712C.18813CC3@bioinf.man.ac.uk> Date: Tue, 19 Jun 2001 16:35:08 +0100 From: Chris Taylor <Christopher.Taylor@man.ac.uk> Organization: University of Manchester X-Mailer: Mozilla 4.77 [en] (Windows NT 5.0; U) X-Accept-Language: en To: memetics@mmu.ac.uk Subject: Re: sexual selection and memes References: <2D1C159B783DD211808A006008062D3101745F1B@inchna.stir.ac.uk> <3B2F5E10.759C5BF7@bioinf.man.ac.uk> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: fmb-majordomo@mmu.ac.uk Precedence: bulk Reply-To: memetics@mmu.ac.uk
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.
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Here's the abstract just in case anyone cares...
Nature 400, 358 - 360 (1999) © Macmillan Publishers Ltd.
Environmental determination of a sexually selected trait
SIMON C. GRIFFITH, IAN P. F. OWENS & TERRY BURKE
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.
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Chris Taylor (chris@bioinf.man.ac.uk)
http://bioinf.man.ac.uk/ »people»chris
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