[Taxacom] Fwd: Inbreeding, health, and evolution

Wed Feb 12 18:56:29 CST 2014

Hi Michael,
               The real debate isn't whether the founder effect is real or not.  The question is how common or uncommon it is.  I suspect it may be less common than Mayr might have thought, but more common than his critics realize.  However, common or uncommon it might be, it is still a good example of how inbreeding is not always bad.                               ----------------Ken Kinman
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> Date: Wed, 12 Feb 2014 18:22:08 +1300
> From: m.j.heads at gmail.com
> To: Taxacom at mailman.nhm.ku.edu
> Subject: [Taxacom] Fwd:  Inbreeding, health, and evolution
> 
> Hi Ken,
> 
> You support founder effect speciation, which was a key premise of modern
> synthesis biogeography. But here is what some geneticists have said about
> it (fom my 2012 book):
> 
>    While many biogeographers have accepted the argument [Mayr on founder
> effect and 'genetic revolution'] from genetics, geneticists themselves have
> been less convinced. Tokeshi (1999) argued that the genetic founder effect does
> not seem to be an effective means of speciation and Nei (2002) cited 'one
> of the most important findings in evolutionary biology in recent years:
> that speciation by the founder principle may not be very common after all'.
> Orr (2005) wrote that despite the early popularity of the idea, 'it is
> difficult to point to unambiguous evidence for founder effect speciation,
> and the idea has grown controversial'. The experiments of Moya et al.
> (1995) failed to corroborate predictions of founder effect speciation and
> subsequent studies have also found no evidence for it (Rundle et al., 1998,
> Mooers et al., 1999, McKinnon and Rundle, 2002, Rundle, 2003). Crow (2008)
> called the idea of genetic revolution 'vague and misguided' (see also Crow,
> 2009).  Even in birds, founder effects 'may be unnecessary' (Grant, 2001,
> cf. Walsh et al., 2005). The passerine *Zosterops* is often cited as the
> classic case of a taxon that has evolved by founder speciation (Mayr and
> Diamond, 2001), yet a detailed study of clades in the south-west Pacific
> concluded that the focus on founder effects in this group 'has been
> overemphasized' (Clegg et al., 2002).
>    Florin (2001) described how 'The vicariance model of allopatric
> speciation has been repeatedly confirmed empirically, while peripatric
> [founder effect] speciation has suffered severe criticism for being both
> implausible and empirically unsupported'. In her own studies on flies she
> found 'no support for speciation through founder effects'. In recent years
> the debate has heated up and advocates of dispersal theory have found it
> necessary to publish an article stressing 'The reality and importance of
> founder speciation in evolution' (Templeton, 2008). This was a reply to
> Coyne and Orr's (2004: 401) conclusion that 'there is little evidence for
> founder effect speciation'. Coyne (1994) wrote that the idea  'has infected
> evolutionary biology with a plague of problematic work'.
> 
> Michael
> 
> 
> 
> On Wed, Feb 12, 2014 at 3:41 PM, Ken Kinman <kinman at hotmail.com> wrote:
> 
> > Dear All,
> >         The whole debate over Marius the giraffe, got me thinking again
> > about something I hadn't looked at in many years.  Although the risks of
> > inbreeding are real, especially when it is repeated sequentially over
> > several generations, have those risks been overstated (especially in the
> > first or second generation)?  If the risk increases from 2% to 4% for first
> > cousins mating, that is an increase of 100%.  Yikes!!!???  But is 4% versus
> > 2% something to getting overly excited about, especially in a non-human
> > species like giraffes?
> >         If Marius the giraffe posed an increased risk of health problems
> > in his progeny that was 4% versus 2%, does that even justify eliminating
> > him from breeding (much less killing him outright?).  Geneticists might say
> > that this is a 100% increase in risk, but are they statistically
> > exaggerating the risks (not only to other researchers and the public at
> > large, but perhaps in their own minds as well)?
> >         And as those of us who study evolution of species, do we too often
> > overlook how often species arose from the "founder effect"?   Many have no
> > doubt resulted from just a few individuals (or even just a single pregnant
> > female) being isolated on an island or isolated area.  And in spite of the
> > obvious inbreeding, a new species is created and can even thrive.  Why???
> >  Because inbreeding can not only increase the frequency of bad genes, but
> > sometimes can increase the frequency of extremely beneficial genes as well.
> >       If we are to be open-minded scientists, shouldn't we be looking much
> > harder at such potential benefits, and that the religious prohibitions
> > against matings between third, second or even first cousins, may apply in
> > certain cases, but not the extreme risk it is so often made out to be.  In
> > many cases, the risk may overall be neither particularly negative or
> > positive.  In which case, the preoccupation of geneticists relating to
> > Marius and giraffe populations, may be overly exaggerated.  We will never
> > know in the case of Marius since they prejudged this healthy individual as
> > a genetic risk (perhaps ultimately based on statistics which were
> > exaggerated by some scientists, even though it may have not been
> > exaggerated intentionally). Below is a weblink to just one single
> > discussion of such unresolved scientific questions.
> >                     ----------------------------Ken Kinman
> >
> > http://theconversation.com/birth-defect-risk-for-children-of-first-cousins-is-overstated-15809
> >
> >
> >
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> >
> 
> 
> 
> -- 
> Dunedin, New Zealand.
> 
> My recent books:
> 
> *Molecular panbiogeography of the tropics.* 2012. University of California
> Press, Berkeley. www.ucpress.edu/book.php?isbn=9780520271968
> 
> *Biogeography of Australasia:  A molecular analysis*. 2014. Cambridge
> University Press, Cambridge. www.cambridge.org/9781107041028
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> Celebrating 27 years of Taxacom in 2014.