[Taxacom] Fwd: Inbreeding, health, and evolution
Fred Schueler
bckcdb at istar.ca
Wed Feb 12 19:13:50 CST 2014
On 2/12/2014 7:56 PM, Ken Kinman wrote:
> 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
* but in the present case, the goal is to preserve existing lineages of
Giraffes, not to create a new kind.
http://www.ibtimes.com/copenhagen-zoo-kills-giraffe-marius-case-highlights-difficulty-maintaining-genetic-diversity-1554421
fred.
=================================================
> ----------------------------------------------------------------------------------------------------
>> 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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>>> Celebrating 27 years of Taxacom in 2014.
>>>
>>
>>
>>
>> --
>> 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.
>
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>
> Celebrating 27 years of Taxacom in 2014.
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Frederick W. Schueler & Aleta Karstad
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