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Greatest Show on Earth - The Guppies - Comments

Sean_W's Avatar Comment 1 by Sean_W

What does it matter if the male is eaten? It can't take very many of them to create lots and lots of guppies.

Fri, 08 Oct 2010 09:51:47 UTC | #530698

Frenger's Avatar Comment 2 by Frenger

You are looking at it a little confused. Remember, evolution and natural selection doesn't have a plan. There has to be a balance between natural selection (in this case survival) and sexual selection.

So, if all the male fish were a less obvious colour then the females would pick a male on other attributes, say size or whatever.

But then, a fish with a slightly brighter pattern would come along and would instantly grab the attention of the other females ensuring his DNA gets passed on.

That offspring would then have the genes of a brighter more colourful pattern and repeat.

It balances when patterns get so bright that they don't survive to sexual age because they get easily picked off by predators.

I hope that makes sense.

Fri, 08 Oct 2010 10:08:27 UTC | #530711

Et's Love Child's Avatar Comment 3 by Et's Love Child

What I would do is find out who wrote the book, then drop that person a wee note asking them to explain themselves. Be firm but fair when penning it, and a "just because it is daddio" is no acceptable answer.

It's this kind of thing that brings serious study/science into disrepute, and not doubt I too will have sleepless nights now.

ELC

Fri, 08 Oct 2010 10:13:58 UTC | #530713

Louise43's Avatar Comment 4 by Louise43

Comment 2 by Frenger :

You are looking at it a little confused. Remember, evolution and natural selection doesn't have a plan. There has to be a balance between natural selection (in this case survival) and sexual selection. So, if all the male fish were a less obvious colour then the females would pick a male on other attributes, say size or whatever.

But then, a fish with a slightly brighter pattern would come along and would instantly grab the attention of the other females ensuring his DNA gets passed on. That offspring would then have the genes of a brighter more colourful pattern and repeat.

It balances when patterns get so bright that they don't survive to sexual age because they get easily picked off by predators. I hope that makes sense.

Yes complete sense, thank you.

Not sure about posts 3 & 4 though. Are they showing up in the wrong thread as they appear to be addressing something else entirely?

Fri, 08 Oct 2010 10:53:32 UTC | #530733

GerhardW's Avatar Comment 5 by GerhardW

It´s hard to attract females with your strong an big body, if you live in dark shadowed waters or a green algae soup where the shape of your body is hard to spot. But if you have bright green, red and/or blue spots, you can attract females from a far wider region. And if you´re a female Guppy, your male offspring will have better chances in reproduction if you look for a father with bright shiny colours.

Fri, 08 Oct 2010 10:53:38 UTC | #530734

DamianIcely's Avatar Comment 6 by DamianIcely

I haven't read the book yet (bought it for my dad but haven't managed to have a sneaky read!).

That said there may be "peacock effect" at work. Proving your fitness by using a costly advert. In this case the fact that you haven't been eaten despite having a big "eat me if you can" colouring proves that you must be a good swimmer.

Fri, 08 Oct 2010 14:40:22 UTC | #530882

bachfiend's Avatar Comment 7 by bachfiend

Another explanation is that bright colours are a sign of good health. A male guppy who is also able to survive in spite of being obvious in its environment also has to be very fit, able to swim faster, be more alert to avoid potential predators.

Fri, 08 Oct 2010 19:53:28 UTC | #531047

Only Human's Avatar Comment 8 by Only Human

Hello folks, This is my first post here. Natural selection and sexual selection tug to and fro, sexual selection is favoured when other predatory or environmental selection pressures are low. When remaining hidden is a stronger selection pressure than impressing a mate,then sexual selection (that works) shifts away from flamboyance towards other viability indicators. Females may still be attracted by the shiniest male, but predatory selection pressure will make the males all more dowdy; she'll pick the best of what's available.

Sat, 09 Oct 2010 00:13:15 UTC | #531136

Yan's Avatar Comment 9 by Yan

Remember that such male guppies only have the opportunity to evolve exquisite colours BECAUSE there are limited predators in their habitat. So I suppose the benefit of attracting a female and passing on genes far outweighs the comparatively minor risk of being preyed upon. Conversely, guppies who live in a habitat with a high guppy:predator ratio are more likely to be dull. It's all in the balance.

Sat, 09 Oct 2010 00:21:51 UTC | #531140

Only Human's Avatar Comment 10 by Only Human

True, apart from the idea that sexual selection outwieghs natural selection. You don't get to breed if you're lunch. It's NOT in a balance, it's a war out there. Consider the Prisoners Dilemma.

Sat, 09 Oct 2010 01:16:08 UTC | #531154

Only Human's Avatar Comment 11 by Only Human

Sorry that's not quite right.

Sexual selection is a prime mover of evolution, if it isn't outcompeted by other, more immediate factors. For instance, there are many selection pressures amongst all species upon the African plain. Many of those pressures come from outside one's own species, what Dawkins refers to as The Extended Phenotype. In a nutshell, changes in another species can directly affect anothers genes due to predatory or other selection pressures. In newer habitats like New Zealand ro Galapogos, sexual selection has played a pivotal role in the absense of other selection stresses.

Sat, 09 Oct 2010 01:35:36 UTC | #531157

Anaximander's Avatar Comment 12 by Anaximander

It is also possible that they are less colorful most of the time and only gets bright colors when needed.

Sat, 09 Oct 2010 06:27:18 UTC | #531191

Alan4discussion's Avatar Comment 13 by Alan4discussion

I have not read the book, but it seems to me that given that fish produce large numbers of offspring, sexual selection of even remaining reduced numbers of high-viz males would prevail. A significant factor could be that females would get a measure of protection by the selective sacrificial predation of males, thus producing more offspring because of a higher female percentage of the fish population. This would not apply in species where the males protect the "nests" or the young.

Sat, 09 Oct 2010 12:03:54 UTC | #531259

Roedy's Avatar Comment 14 by Roedy

What you say is true of Rainbow Lizards in South Africa, but not of guppies. The colours in the male guppy are the result of artificial selection. The breeder mates a colourful male with his daughters, granddaughtmers, great granddaughters etc. Guppies in the wild are quite dull, though the males are slightly more colourful.

Here a possible explanation, that made up myself. I have no idea how the pros would react to it. In the Rainbow Lizards, the females mate with only one male, and one or two prettiest males do most of the breeding. The rest of the males are dispensable. By making them bright, predators will go after the useless males more than the necessary females.

Here is another idea, to be an alpha male, you have to stand out from the crowd. Just being strong is not enough. You need some flash.

Imagine yourself signing up for a dating service. There are 10,000 candidates to look at. Only the ones who are in some way outstanding will attract your interest. The colours are an edge in this game, even if it hurts in the predator game.

One more thing to consider is most animals don't have colour vision. So a colourful display might look like camouflage to a black and white vision predator.

Sun, 10 Oct 2010 08:11:33 UTC | #531538

Roedy's Avatar Comment 15 by Roedy

This is not germane to your question, just to guppies.

Male guppies, when rejected by females, are not in the least deterred. They just try again or try another female. I have never seen one pine.

Humans on the other hand, get hit with one rejection, and can go off for weeks in retreat, humiliated. This even happens to gay people.

Why are humans so different from other animals?

Sun, 10 Oct 2010 09:46:55 UTC | #531556

pflm's Avatar Comment 16 by pflm

I haven't read the book yet ...

That said there may be "peacock effect" at work. Proving your fitness by using a costly advert....

The female guppy hasn't read the book either, so I don't really like the fairly sophisticated piece of reasoning required for your explanation to work. Consider what is more likely in the brain of a female guppy:

a. male A has larger spots than male B => male A is more of a target for predators than male B => male B must be fitter => if I breed with male A the quality of the genes in my offspring will be greater

OR

b. phwwoooaar!!!

Presumably female guppies are attracted to mate with things that look like male guppies, and the more male they look the more likely the females are to mate with them. If having coloured spots is a marker for being a male guppy, then the genes for having these spots will persist through the generations of guppies, nicely balanced by the rate at which males which are very colourful get munched by predators before they can breed.

Sun, 10 Oct 2010 12:40:40 UTC | #531583

Anaximander's Avatar Comment 17 by Anaximander

The female guppy hasn't read the book either, so I don't really like the fairly sophisticated piece of reasoning required for your explanation to work.

Yes, it's clear that they don't actually (probably) think that way. But we are trying to find the logic of this from the gene perspective.

Sun, 10 Oct 2010 20:36:25 UTC | #531750

pflm's Avatar Comment 18 by pflm

Yes, it's clear that they don't actually (probably) think that way. But we are trying to find the logic of this from the gene perspective.

Genes have also not read the book.

It is a fairly sophisticated piece of logic required for the peacock effect (as described by DamianIcely) to work, which is why I do not like it as an explanation. It also requires a fairly sophisticated weighing-up of the odds between the probability of the offspring being eaten before they breed v. the extent to which the display shows their fitness. Humans are known to be very bad at judging probabilities and risks, I doubt guppies are much better at it.

I prefer an explanation based on female guppies being attracted to breed with things that look like male guppies. If being patterned is a characteristic of male guppies then baby male guppies born with genes promoting patterning will have an advantage in breeding during the next generation, but only if they survive long enough.

I think it is fairly clear that genes promoting behavior "breed with the most male-looking thing you see" would be strongly selected for.

Mon, 11 Oct 2010 12:32:31 UTC | #532020

Anaximander's Avatar Comment 19 by Anaximander

Genes have also not read the book.

I think, no, I guess, that genes don't think. They build an organism that follows some strategy. If that strategy happens to be good, those genes are successful.

There is no need for the genes or the organism to understand why the strategy is good.

Mon, 11 Oct 2010 16:39:19 UTC | #532106

Louise43's Avatar Comment 20 by Louise43

Almost at the end of the book now and I think it's starting to sink in - there is no plan. I just had to change how I was thinking. But that's not easy when you're a member of a rather ego centric species.

Mon, 11 Oct 2010 19:48:42 UTC | #532171

Frenger's Avatar Comment 21 by Frenger

Comment 17 by pflm :

a. male A has larger spots than male B => male A is more of a target for predators than male B => male B must be fitter => if I breed with male A the quality of the genes in my offspring will be greater OR

b. phwwoooaar!!!

Probably my favourite ever explanation sexual selection I have ever read.

Tue, 12 Oct 2010 13:08:58 UTC | #532419

DavidMcC's Avatar Comment 22 by DavidMcC

Here's a very late contribution, but it is really only repeating what I said in my own thread on TGSOE some time ago. Male guppies are only brightly patterned when there are few predators about to be a threat. In those circumstances it makes sense to flaunt yourself, because the ruisk is low. If the predators return, then, in an evolutionary blink of the eye, the camourflage returns. This, I strongly suspect is due to the evolution of an epigenetic response to some chemical left in the water by the predator.

Wed, 22 Jun 2011 11:16:56 UTC | #641632