William Morse wrote:
> wirtatmar{at}aol.com (Wirt Atmar) wrote in
> news:cpvp7u$1m83$1{at}darwin.ediacara.org: 
> 
> 

>>
>>Although Alexy Kondrashov has compiled 27 different advantages
>>attributed to sexual reproduction in the literature, the big three
>>remain: 
>>
>>     o rapid phyletic adaptation to novel conditions
>>     o the escape from parasites due to genetic diversity

Aren't these two are really the same thing: the ability to adapt to 
changing environment?

>>     o a mechanism that combats the aging of the germline
>>
>>Which of these is true? All of them are. It's not a "tastes
>>better/more filling" kind of argument, but without the last advantage,
>>a phyletic lineage would soon decay into nothingness, in the same way
>>that xerox copy of a xerox copy soon decays into a page of illegible
>>black and white dots after just a few dozen replications, and this is
>>the principle reason that apomictic populations, especially complex
>>organisms, tend to only exist for very short periods of time.
> 
> 

> 
> But it does appear that facultative parthenogenesis is not that rare (based 
> on a quick search on Google Scholar), so it might be interesting to pursue 
> the conditions for facultative parthenogens which favor asexual vs. sexual 
> reproduction. A greater degree of heterozygosity is apparently one 
> condition, which agrees with your big three. Another (among Timema -walking 
> sticks- in California) was being at the northern extent of the range. Is 
> this based on reproductive advantage overcoming parasite resistance at the 
> limit of the range, where parasite resistance is not that important, or is 
> it due to some temperature effect on development?  
> 
Has anyone looked seriously at fungi in this regard?  Many of them are 
able to reproduce both sexually and azexually, so there should be scope 
for comparative studies?

A quick google brings up this:
http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.phyto.37.1.197>
but it seems to approach the problem from an applied perspective.  I 
suspect that an analysis of _when_ species enter their sexual/asexual 
phase may be interesting.  If only I had the time....

Bob

-- 
Bob O'Hara
Department of Mathematics and Statistics
P.O. Box 68 (Gustaf Hällströmin katu 2b)
FIN-00014 University of Helsinki
Finland

Telephone: +358-9-191 51479
Mobile: +358 50 599 0540
Fax:  +358-9-191 51400
WWW:  http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: www.jnr-eeb.org
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