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Re: Alpha Male Breeding Success
Apologies to those who dislike the keeping of a whole string of ideas
I'm afraid I'm still not completely clear on a couple of your points
below. It makes perfect sense from a betta breeders point of view. The
goal there is to take one desirable (breeder's desire) pair of fish and fix
a set of genes to consistently produce a particular strain. In that case to
dilute the genes with another male's is bad. I thought with killies our
goal is try and preserve a group's diversity. It seems that keeping some of
the B male's genes going would be a good thing. Fish A might not possess
all the genes we wish to preserve. Of course, the limited population we can
keep pretty much forces the breeders to make selections anyway, and
guarantees loss of diversity. Many select for color or size of fins, etc.
so our preferences for appearance supercede nature's. I agree that gang
spawning seems the least bad compromise and is my preference when I can do
so as well. Thanks for the lessons.
----- Original Message -----
From: "Doug Karpa-Wilson" <dkarpawi at indiana_edu>
To: <killietalk at aka_org>
Sent: Thursday, December 14, 2000 11:11 AM
Subject: Re: Alpha Male Breeding Success
> Hey, Jay,
> Sure! The important bit is that if you have a lot of AX offspring
> BX's will contribute more than other AX's since they're redundant.
> Whichever is the rarer type will contribute more. Think about it from the
> point of view of what proportion of genes from each of the parents are
> retained in the next generation. Just to keep the argument intelligible,
> let's assume both the females reproduce equally, so we can focus on the
> males. On average the females will leave two offspring each (Unless the
> tank space is continuously expanding over the protests of spouses who have
> to now keep their sweaters in the unheated garage ;-).
> For the sake of argument, let's stay with 2 offspring each. Let's say
> A has his first offspring (A1). He will contribute half his genes (one
> copy of each of the thousands of genes the species has) to the first
> offspring. Total genes of his retained: 1/2 of his genome (one copy of
> each gene).
> The second offspring will also have half his genes, but since they come at
> random, half the genes A passes on to the second offspring (A2) will be
> same ones he passed on to A1, so only half of the genes in A2 are genes
> that would have been lost if A hadn't had the second offspring. Total
> retained in A1 and A2: 3/4 of A's genes.
> The third offspring will also retain 1/2 A's genome, but 3/4 of that half
> are copies found in A1 and A2 as well, so the part of A's genome that A3
> preserves uniques amounts only to 1/8 of A's genome. Total saved 7/8 of
> genome. As you can see trying to keep a copy of every single on of A's
> genes becomes very hard.
> Since we're limited in the total number of offspring that we can keep,
> third offspring comes at the expense of B having a second offspring.
> A gets 3 offspring retaining 7/8 of A's genes, but now B gets only 1 so
> only 1/2 of his genes are preserved. In order to get 1/8 of A's genes we
> gave up 1/4 of B's.
> The general priniciple is that the more variation there is among the
> numbers of offspring among individuals the faster genes are lost. It gets
> more complicated than that, for sure, when you start keeping track of the
> differing amounts relatedness among individuals (for example, A1 and A2
> have one quarter of their genes in common because of their common sire,
> while A1 and B1 have none, so breeding A1 and B1 is better than A1 and A2,
> but you knew that!).
> There is also the important Wright principle that if wild killies are
> totally inbred none of this matters. In that case, A and B are
> identical, so it doesn't matter who mates with whom since there aren't any
> different versions to retain. Every individual has all the genes of the
> entire population. This takes a long time, and it takes very little gene
> flow to prevent it.
> The issue you raise about gene combinations (i.e. AX, AY, BX,BY stuff) is
> actually cutting edge genetics, but it may not be so important to simply
> retaining as many versions of genes as possible. Of course, for the super
> hyper types, the way to go would be to breed both males with both females
> so you have known parentage and keep one offspring from each cross.
> It should be noted that I gang spawn my fish! Of course, they're all sibs
> (i.e. very similar) and I'm not a serious large scale breeder. I am only
> really paying attention to output from a single species right now.
> I hope I haven't offended anyone here, but I'm sure I have somehow.
> > I know you have more training by far than I do in genetics. I am
> >not fully following the math here on the loss of diversity. So, I'm
> >for a bit more clarification. If I have a group consisting of males A
> >and females X and Y and A is dominant, then we would intuitively expect B
> >be unsuccessful in passing on his genes. All offspring from the group
> >be either AX or AY genetically. If B is sneaky enough to get his genes
> >the mix, then some fry would be BX and BY and some would still be AX and
> >To me that looks like an increase in genetic diversity. It also seems
> >if the pairs are separated into two tanks, A with X and B with Y, then
> >offspring will be limited to AX and BY. This also seems like a loss of
> >total genetic diversity. Can you more fully explain how this is actually
> >not true, and results in less genetic diversity? Thanks.
> >Jay Moylan
> >----- Original Message -----
> >From: "Doug Karpa-Wilson" <dkarpawi at indiana_edu>
> >To: <killietalk at aka_org>
> >Sent: Wednesday, December 13, 2000 12:17 AM
> >Subject: Re: Alpha Male Breeding Success
> >> >
> >> > I stand by what I said about the unexpectedly high success
> >> >non-dominant males in the spawning of many species. Some species have
> >> >25-50% success by non-dominant males in species with clearly dominant
> >> >males who violently repell competitors
> >> >Jay Moylan
> >> More than you'd expect, as in more than zero. The simple fact remains
> >> gangspawning where some of the males are getting only 50% of their
> >> means that you are losing the genetic diversity quite a bit faster than
> >> you bred them individually.
> >> Doug
> >> Doug Karpa-Wilson
> >> Department of Biology
> >> Indiana University
> >> Jordan Hall
> >> 1001 E. 3rd St.
> >> Bloomington, IN 47405
> >> ---------------
> >> See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
> >See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
> Doug Karpa Wilson
> Department of Biology
> Jordan Hall
> Indiana University
> Bloomington, IN 47405
> See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
See http://www.aka.org/AKA/subkillietalk.html to unsubscribe