Amazon mollie theory
#1 Guest_Bob_*
Posted 10 April 2009 - 12:07 PM
I think you need to subscribe to the site, before you can view it, but here's the link anyway: http://www.the-scien.../display/55611/
Basically, amazon mollies (Poecilia formosa) are a parthonogenic species. The species consist entirely of females, which are pretty much genetic copies of the mothers. Although they don't incorporate male genetic material into their eggs, female amazon mollies do need to mate with males of other species (either the sailfin mollie, P. latipinna, or the shortfin mollie, P. Mexicana) before their eggs will develop into baby female fish. Amazon mollies are thought to have resulted from a long ago cross of the two species.
What scientists don't understand is why all three species don't go extinct. Theoretically, the ever increasing proportion of females should use up all the available males, preventing them from mating with females of their own species, causing a population crash.
This doesn't happen. The researchers theorize there are several reasons why. First, the Amazon species and the two species may occupy different habitats, and only come in contact periodically. Second, males are thought to be able to distinguish between females of their own and a P. formosa, and preferentially mate with their own species. (In support of that hypothesis, I think I remember a study claiming that the males only mate with P. formosa females in an effort to increase their marketability with females of their own species--inciting piscine jealousy, in fact.)
The scientists do note that in spite of these potential safegaurds, populations do periodically go extinct at a local level. But since the ranges of P. latipina and P. mexicana extend far beyond that of the range of P. formosa, there are reservoirs of males to extend into the range of P. formosa and make up for the lost males of their own species.
#2 Guest_AndrewAcropora_*
Posted 10 April 2009 - 05:15 PM
Why would parthenogenesis evolve if you still need a male? It seems that having all of your species being able to reproduce but still being reliant upon a male would be a serious problem.
#3 Guest_fundulus_*
Posted 10 April 2009 - 07:00 PM
#4 Guest_AndrewAcropora_*
Posted 10 April 2009 - 07:59 PM
My confusion stems from the article saying a sperm from a related species' is required.
....To initiate embryogenesis, however, Amazon mollies require sperm from the males of one of two closely related, but sexually reproducing, species sharing their habitats in southern Texas and northern Mexico -- the sailfin molly (Poecilia latipinna) or the shortfin molly (Poecilia mexicana)....
Does anyone know if the sperm is actually binding with an egg or is it the stimulation that does the deed? Perhaps the article has misquoted someone?
Finding a female when all of your comrades are female is easy, but if you still need a male---what's the advantage? I would assume higher reproductive output, but there has to be a bottleneck since a male is still required.
#5 Guest_fundulus_*
Posted 10 April 2009 - 09:36 PM
The sperm doesn't bind with the egg, but does a series of "molecular handshakes" with the egg exterior without penetrating the egg and triggers embryogenesis. The situation isn't purely adaptive, since the species is descended from sexually reproducing ancestors and carries that baggage. Does it maximize fitness? Probably not in the long run, but if a given genome works it could be a case of if it ain't broke don't fix it. Field work has been conducted with Amazon mollies and their near relatives demonstrating that the sexually reproducing species can adapt much better to stresses like novel parasites or drought. It's still unclear what benefits a population gains by going off on such an odd adventure and abandoning meiosis/sex, going against over 2 billion years of eukaryotic cells fine-tuning meiosis (and sex as a mechanism to make it work better).Does anyone know if the sperm is actually binding with an egg or is it the stimulation that does the deed? Perhaps the article has misquoted someone?
Finding a female when all of your comrades are female is easy, but if you still need a male---what's the advantage? I would assume higher reproductive output, but there has to be a bottleneck since a male is still required.
And my compliments to your mother, she needn't worry...
#6 Guest_rjmtx_*
Posted 11 April 2009 - 01:23 AM
I think a lot of oddities (and some normalities) in this world aren't selected for, but fail to be selected against.
#8 Guest_Newt_*
#9 Guest_oscarbartoni_*
Posted 22 April 2009 - 01:53 PM
#10 Guest_Bob_*
Posted 23 April 2009 - 04:44 PM
They have found a few male specimens once in a while. They are working with these to try and mate with the females to see if that has any effects. They are working bout with artificial and natural fertilization. I have not heard any results yet on this but it is interesting.
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