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 The Red Queen Hypothesis

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Tom D
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PostSubject: The Red Queen Hypothesis   Tue Feb 26, 2013 7:44 am

The current discussions of using outliers to stay in the same place, and the need for variation in closed populations brought this to mind from my college days. I have a book about this buried somewhere, but I'm pretty sure it was excruciatingly boring, so I just grabbed a couple paragraphs from Wikipedia.



The Red Queen hypothesis, also referred to as Red Queen's, Red Queen's race or Red Queen Effect, is an evolutionary hypothesis which proposes that organisms must constantly adapt, evolve, and proliferate not merely to gain reproductive advantage, but also simply to survive pitted against ever-evolving opposing organisms in an ever-changing environment. The Red Queen hypothesis intends to explain two different phenomena: the constant extinction rates as observed in the paleontological record caused by co-evolution between competing species[1] and the advantage of sexual reproduction at the level of individuals.[2]


The original idea of the Red Queen hypothesis (macroevolutionary) was given by Leigh Van Valen in order to explain the “Law of Extinction”.[3] Leigh Van Valen showed that in many populations the probability of extinction does not depend on the lifetime of this population. In addition, the probability of extinction is constant over millions of years for a given population. This could be explained by the coevolution. Indeed, an adaptation in a population of one species (e.g. predators, parasites ...) may change the selection pressure on a population of another species (e.g., prey, hosts), giving rise to an antagonistic coevolution. If this occurs reciprocally, a potential dynamic coevolution may result.[4] He called that idea the “Red Queen hypothesis” in reference Red Queen's race in Lewis Carroll's Through the Looking-Glass because species had to evolve in order to stay in the same place.[5]


The macroevolutionary Red Queen. The linear relationship between number of genera and the logarithm of survival times suggests that the probability of extinction is constant over time. Redrawn from Leigh Van Valen (1973).
In another idea (microevolutionary), the Red Queen hypothesis is used by Bell to explain the evolution of sex[6], by John Jaenike to explain the maintenance of sex [7] and W. D. Hamilton explain the role of sex in response to parasite.[8] In all cases, sexual reproduction allows to create variability and a faster response to selection by making offspring genetically unique. Sexual organisms are able to improve their genotype in function of changing conditions. Consequently a co-evolutionary interactions, between host and parasite for example, may select for a sexual reproduction in hosts in order to reduce the risk of infection. Oscillations in genotype frequencies are observed between parasites and host in an antagonistic coevolution way. Once again, the two stay at the same place.

Science writer Matt Ridley popularized the term "the red queen" in connection with sexual selection in his 1993 book The Red Queen. In the book, Ridley discussed the debate in theoretical biology over the adaptive benefit of sexual reproduction to those species in which it appears. The connection of the Red Queen to this debate arises from the fact that the traditionally accepted theory (Vicar of Bray) only showed adaptive benefit at the level of the species or group, not at the level of the gene (although, it must be added here that the protean "Vicar of Bray" adaptation is very useful to some species that belong to the lower levels of the food chain). By contrast, a Red-Queen-type theory that organisms are running cyclic arms races with their parasites can explain the utility of sexual reproduction at the level of the gene by positing that the role of sex is to preserve genes that are currently disadvantageous, but that will become advantageous against the background of a likely future population of parasites.

Sex is an evolutionary puzzle. Sexual organisms must spend resources to find mates. In the case of sexual dimorphism, usually only one of the sexes, sometimes females sometimes males, contribute to the survival of their offspring. In such cases the only adaptive benefit of having another sex is the capability of sexual selection, by which organisms can improve their genotype. In this way, sexual reproduction can be highly inefficient.

For sex to be advantageous for these reasons requires constant selection for changing conditions. One factor that might cause this is the constant arms race between parasites and their hosts. Parasites generally evolve quickly because of their short life cycles. As they evolve, they attack their hosts in a variety of ways. Two consecutive generations might be faced with very different selective pressures. If this change is rapid enough, it might explain the persistence of sex.
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Grassfarmer



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PostSubject: Re: The Red Queen Hypothesis   Thu Feb 28, 2013 12:03 am

Maybe the wrong place to air these questions again but I still don't get it on the topic of using outliers to stay in the same place and the need for variation in closed populations. Remember I didn't go to college so use short words and simple concepts to explain it to me. Lets develop a "red bull hypothesis" Smile

If you are talking about a closed maternal population how do you even select the outlier bulls? If you identify the outliers on phenotype or growth rate are they really genotype outliers or merely exhibiting the range of variation possible with their gene pool and isn't there a good chance their offspring within the closed population will revert to the average of the gene pool? I guess with the passage of time you could identify the ones that were outliers by their offspring - if their daughters only lasted to 7 years old or if they lasted to 17 years old - but that's cutting into your cattle breeding lifetime. How do you even identify the outliers in a maternal situation?

Similar scenario with the question on the need for variation in a closed population. If you accept that there is a need to maintain variation or potential "corrective factors" within the population how do you know that what you see is what you will get? If the genotype is close how predictably variable will any animal you select be for any characteristic.

I'm confused. I have 5 bull calves that are 7/8ths brothers, very much peas in a pod. I might need to keep one as a potential replacement for his sire but have no clue which to pick other than the ones that do most running up and down the fence trying to get to cows. There was one notably different at weaning - it was out of an undersized close-bred heifer and I never thought it a serious contender being considerably smaller and lighter. He was lighter at birth too. Weighed them recently and there was 10lbs between the heaviest and lightest despite 2 months separating youngest and oldest. So is the one that started out lighter an outlier? Is he an outlier for growth because he caught up with the rest or is that just environmental influence of the way he was raised? Or does this show that he is reverting to the average of the gene pool and he will likely breed that way? Not that weight is likely all that important for selecting maternal anyway.
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MKeeney
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PostSubject: Re: The Red Queen Hypothesis   Thu Feb 28, 2013 1:02 am

Iain,
couple quick midnight clarifications...I`m speaking primarily in performance/weight terms, but then also I believe vigor is upheld better, and a "closed line" prolonged by use of those above the mainline rather than below it...I`m calling a 105 ratio an outlier, and a 115 a cull...because if by chance a 115 is created, 115 will likely upset the balance of the line...
so it is 105 versus the 95...the 95 might make the genotype more "pure", but I don`t think it upholds the phenotypic level...theory dependent on believing that homozygousity is increasing faster in the 95`s rather than the 105`s...
you are probably even more confused with my saying, and I`m not saying I`m right, just thinking out loud...
as to which of the 5 bulls to use? is why I sing "oh for a thousand cows to breed "... cheers
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Danny Miller



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PostSubject: Re: The Red Queen Hypothesis   Thu Feb 28, 2013 7:03 am

Interesting thread, GF sounds like you could chose any one of those brothers and do just fine. I would probably select the one with
the dam I liked best....Which could still present a dilemma if the cows were all close in type and productivity. Or you could just gate cut one. Wink
Mike, I have used more bulls in the 98-105 WR range. One resent selection was a bit higher but liked him better for other reasons.
I have sold the highest actual performers in a crop many times if I thought they would move me in a direction I didn't want to go.
Keep in mind the variation is much less here than with herds of numerous different bloodlines. Sometimes people scratch their heads
when I make a comment on a calf mainly because they only notice the greater variation and cannot see slight variation that I see.
I have no problem using the "average" calf if he can maintain what I am trying to achieve.
DM
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MKeeney
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PostSubject: Re: The Red Queen Hypothesis   Thu Feb 28, 2013 7:13 am

mrvictordomino wrote:
Interesting thread, GF sounds like you could chose any one of those brothers and do just fine. I would probably select the one with
the dam I liked best....Which could still present a dilemma if the cows were all close in type and productivity. Or you could just gate cut one. Wink
Mike, I have used more bulls in the 98-105 WR range. One resent selection was a bit higher but liked him better for other reasons.
I have sold the highest actual performers in a crop many times if I thought they would move me in a direction I didn't want to go.
Keep in mind the variation is much less here than with herds of numerous different bloodlines. Sometimes people scratch their heads
when I make a comment on a calf mainly because they only notice the greater variation and cannot see slight variation that I see.
I have no problem using the "average" calf if he can maintain what I am trying to achieve.
DM

Danny,
too bad for Hannah he went to the wrong place to buy his "victors"...he could have used an outlier for udders from you... Smile
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Grassfarmer



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PostSubject: Re: The Red Queen Hypothesis   Thu Feb 28, 2013 9:40 am

So is the little calf that weaned smallest then gained fastest a 95 or a 105? Other than as an assessment of how the winter feeding program is going I'm not really interested in weighing bulls nowadays - the whole idea of a "bull test" of a winter feeding period is terminal selection in my mind. Would selecting the one that responds poorest to this terminal type test not be the best way to select maternal?
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