an588{at}freenet.carleton.ca (Catherine Woodgold) wrote in
news:coebn3$1m1r$1{at}darwin.ediacara.org: 

> "EKurtz" (NoJunk{at}ForgetIt.com) writes:
>> Consider the case of a sexual species into which a parthenogenic
>> female is introduced by mutation. Assuming that she and her immediate
>> offspring survive, and that the population size is constant, her
>> offspring will effectively displace the sexual type in a few dozen
>> generations. 
> 
> Even if the parthenogenetic individuals average only 1.5
> fertile offspring each, they will tend to take over the whole
> population.  The sexual ones could be declining while
> averaging 1.8 offspring each, while the parthenogenetic ones
> grow exponentially at 1.5 offspring each.  So number of
> fertile offspring is not a very useful definition of "fitness".


But what if (as is normally the case for most organisms) the average number 
of offspring (before predation and disease) is on the order of hundreds to 
thousands? In this case the parthenogenetic individuals have very little 
advantage in terms of having more offspring - they invest less energy per 
offspring but that investment is not particularly large - while their 
offspring suffer higher rates of predation and especially disease. Under 
these circumstances (which again are the norm for most organisms) 
parthenogenesis does not have any advantage.


Yours,

Bill Morse
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 12/6/04 6:36:09 AM