Warning Signs and How They Evolve

[Sophus]

I was thinking the other day about poisonous animals and how some have developed "warning signs" to dispel potential predators. Specifically speaking vibrant colors, but they're also other instances, such as the rattle on a rattlesnake. It's obviously beneficially to both the prey and the otherwise predators since, say, a poisonous frog which is eaten will kill the animal eating it. So if the predator recognizes it as a dangerous animal they both live longer and carry on their genes. The more obvious its distinction from other safe-to-eat animals the greater the chance they both have at surviving for a longer duration.
A mutation would have caused a slightly more colorful frog originally. What evolutionary advantage would this give the frog if its prey has yet to establish a habit of avoiding oddly colored prey? The best answer I can come up with is not because they would have had a tendency to avoid such oddly colored food but rather their instincts have already established a fairly consistent diet which they aren't likely to veer from often, thus they might not be as inclined to pursue our mutant froggy for lunch considering it wouldn't look like what is usually on the menu?

[elliebean]

Idk, I just found out yesterday about the Uncanny Valley Effect, which was pretty fascinating in itself. I wonder if it's real and if there's a connection between that and the way animals 'know' instictively which foods to avoid?

[armchair_darwin]

I wouldn’t worry too much that intermediate coloration wouldn’t have an obvious selective advantage.   Perhaps only a slight color difference would be enough for many of the frogs possessing this phenotype to survive.  Further coloration may have developed by mechanism mentioned above, or more probably through more random mutation that eventually produced even more vibrant color and prey avoidance by the predators.  

As far as the dual benefit of prey and predator in this scenario, I think that is less likely.  This might only seem coupled.   Selection has no forethought.  Avoidance by predators is more probably a learned phenomenon, which is not quickly coupled with instinct.  Either the predator’s parents are able to teach such avoidance to their offspring, or learned by trial and error by the predator.  As many predators aren’t successful in every predatory attempt, simply a quick taste may have produced illness but not death, which leads to avoidance.  

Finally we should recognize that it is not the genes themselves that are selected, but the phenotypes that development produces from the genotype that is selected.  There are very few instances of single genes that have any one to one effect that would then be available to selection.  So the concept of genes as entities that have lasting power in evolutionary history is probably not correct (no matter what Dawkins thinks).  It is not the genes that carry on a legacy it is the phenotype.  Genetic regulation usually involves many genes and gene products during development of a particular trait like coloration.   Hope you don’t think I’m being contrary, but simply like such discussions.  Perhaps you would like to follow at http://twitter.com/Armchair_Darwin

[Sophus]

I wouldn’t worry too much that intermediate coloration wouldn’t have an obvious selective advantage.   Perhaps only a slight color difference would be enough for many of the frogs possessing this phenotype to survive.  Further coloration may have developed by mechanism mentioned above, or more probably through more random mutation that eventually produced even more vibrant color and prey avoidance by the predators.  

As far as the dual benefit of prey and predator in this scenario, I think that is less likely.  This might only seem coupled.   Selection has no forethought.  Avoidance by predators is more probably a learned phenomenon, which is not quickly coupled with instinct.  Either the predator’s parents are able to teach such avoidance to their offspring, or learned by trial and error by the predator.  As many predators aren’t successful in every predatory attempt, simply a quick taste may have produced illness but not death, which leads to avoidance.  

Finally we should recognize that it is not the genes themselves that are selected, but the phenotypes that development produces from the genotype that is selected.  There are very few instances of single genes that have any one to one effect that would then be available to selection.  So the concept of genes as entities that have lasting power in evolutionary history is probably not correct (no matter what Dawkins thinks).  It is not the genes that carry on a legacy it is the phenotype.  Genetic regulation usually involves many genes and gene products during development of a particular trait like coloration.   Hope you don’t think I’m being contrary, but simply like such discussions.  Perhaps you would like to follow at http://twitter.com/Armchair_Darwin

Ah... I hadn't thought of it that way. I recall reading in Dawkins' The Blind Watchmaker that a habit, or any sort of behavior really, in an individual could become genetic even if it was not the case in said individual. Perhaps this is the case with the predators of such frogs? Early on one could have survived attempting to eat one of these frogs (especially considering the frogs may not have been as lethal further down the evolutionary timeline) and would have learned from experience to avoid these vibrant colors. And if there were snakes within the same region who begin to develop similar mutations then they too would naturally be avoided by a growing population of birds (or whatever) who are weary of vibrant colors.

Also, wouldn't genes be what makes a phenotype?

Thanks very much for your input. Feel free to critique me again if my thinking's still off.

[Tanker]

I was watching a nature show awhile back and it showed many poisonious animals being attacked if not eaten by young predaters. Turns out that some predatory species don't instictually know which food is bad but try it first. once they realise the black frog with the red marks behind it's eyes (if it lives) taste bad and makes you sick they stay away from those frogs. The red being forever connected with inedable "food". It did show one bird and frog die because the bird couldn't get it out so eating without tasting would remove the less catious eaters from the gene pool.

[AlP]

Some non-poisonous animals have the same warning signals, maybe to discourage predators.

[Heretical Rants]

Yeah, it's more of an, "ooooh, I shouldn't eat that... *gag*" type thing.  You're more likely to get recognised as a bad meal if you're readily recognisable.

Otherwise, being colorful, unless the colors are similar to another species that is poisonous, is a distinct disadvantage, as you are more easily spotted and recognised as a good meal.

I hypothesise that the one poisonous froggie that had several dozen little froggie offspring, all of which were more likely to survive because one of their syblings got eaten, is a likely candidate for how this began.

[pinkocommie]

Yeah, it's more of an, "ooooh, I shouldn't eat that... *gag*" type thing.  You're more likely to get recognised as a bad meal if you're readily recognisable.

Otherwise, being colorful, unless the colors are similar to another species that is poisonous, is a distinct disadvantage, as you are more easily spotted and recognised as a good meal.

I hypothesise that the one poisonous froggie that had several dozen little froggie offspring, all of which were more likely to survive because one of their syblings got eaten, is a likely candidate for how this began.

Well, also keep in mind that being colorful often has advantages pertaining to mating, so while being colorful may be bad in certain circumstances like trying to hide from a predator in a drab environment, those disadvantages might be outweighed by the advantages a more brightly colored male might have in attracting a female or vice versa.

[Heretical Rants]

Yes, like peacocks.

[karadan]

Colour change for communication or camouflage has always fascinated me. I think cuttlefish are awesome.

When we eventually meet ET, that's what they will look like

[Kylyssa]

I studied this phenomenon as a young child because I raised Monarch butterflies(Danaus plexippus).  Monarch butterflies are toxic, due to chemicals their bodies extract from the milkweed they eat as larva.

I started raising Monarch butterflies because I wanted to save the cute striped caterpillars (yeah, I was around four, don't question my reasoning) I found on the milkweed that I often picked for my mother.  So we researched them at the local library and found that they were the larva of the monarch butterfly.  So, for the next six years or so I raised monarch butterflies from eggs and caterpillars found on milkweed plants along with a whole lot of other insects.  My mom was pretty sure I'd become an entomologist.

The Viceroy Butterfly (Limenitis archippus) is a mimic of the Monarch.  They look very similar.  When I was a child, the Viceroy was still thought to be a Batesian mimic but it was later categorized as a Müllerian mimic.  It eats the leaves of willow trees and concentrates salicylic acid in its body which makes it taste horrible but doesn't make it truly toxic.  Its chrysalis also looks like bird crap.  

It's usually a case of individual animals learning not to eat the caterpillars or butterflies.  Once an animal associates something with illness it will usually avoid it in the future.  It doesn't help the individual butterfly but the species.  A few of each generation get sacrificed each season to keep the majority of the species safe.  I wonder if there's any advantage to early breeding butterflies or late breeding butterflies due to the maturation of local wildlife?  For instance, in early spring, perhaps all hunting birds in a certain area are mature adults but in the fall, their offspring are hunting for their first times.

I once ate a bad batch of peanuts while making peanut brittle with my older brother.  We were vomiting for hours.  To this day, I gag at the smell of peanut brittle even though I logically know there's nothing wrong with it.

[SSY]

Excellent post kylyssa, this is a topic which interests me.

Do you think the colour came first or the poison? Just being bright, but not off-putting to predators would get you eaten pretty fast (assuming there are no poisonous bright butterflies before you to teach the predators), so it would seem logical that Monarchs were poisonous, and then the bright ones, being more distinctive but still noticeably like the other Monarchs formed a stronger negative association in the mind of their predators, and thus, other bright ones were more likely to survive. This makes sense to me on a superficial level, but it does seem similar to group selection, which is something I am a little wary of.

For example, if one were born with an atavism, to be dull (presumably like their ancestors), would that convey a selective advantage? It would make you less likely to be spotted in the first place, and therefore less likely to be eaten by young, untaught predators. However, the animal may be eaten by something else, which knows monarchs are poisonous, but does not recognise this dull one as poisonous.

The combination of these two mechanisms (as I have imagined them, which could be complete fiction) could produce an interesting effect. It would be advantageous to be just a bit duller than the other monarchs. Being still obviously poisonous would protect you from being eaten by older, taught predators, but being a little duller would decrease your chances of being picked out among a host of other Monarchs (am I right in thinking Monarchs swarm in vast numbers?). Could this trend not drive down the brightness over successive generations, trying to find a happy balance between being obvious enough to form negative associations but dull enough to avoid some incidental predation? Presumably, at least some predators are clever enough not to need really bright signals to form these associations? More thought required on my part. . .

Interestingly, wiki says

A color variation has been observed in Australia, New Zealand, Indonesia and the United States as early as the late 1800s. Named nivosus by Lepidopterists, it is grayish white in all areas of the wings that are normally orange. Generally it is only about 1% or less of all monarchs, but has maintained populations as high as 10% on Oahu in Hawaii, possibly due to selective predation.[14]

This is interesting, because it suggests certain predators still eat the Monarchs, and they prefer, normal, orange ones as opposed to silver ones, at least in some places. Why would this be? They should both be equally poisonous, so why avoid silver in favour of orange? Simply their greater abundance, assuming a predator had a way to deal with the poison?

Also, if you have a headache, and eat a viceroy, would that ease the pain? I think I would rather the headache.

[Kylyssa]

Yes, Monarchs tend to gather in great numbers.

I wonder if the abnormally pigmented Monarchs of Hawaii are benefiting from  having different predators?  If predators on Hawaii are able to recognize Monarchs by both their color and their pattern/shape instead of just by their color, the low pigment butterflies might not have the same disadvantage they'd have elsewhere.

I think that either the color or the toxin could have come first.  The patterning probably came first as it is similar to that of many other butterflies.  The toxin may have been more likely to come first and the coloring later as the butterfly without the bright color would be toxic but not as easily recognizable thus the easily recognizable ones would tend to dominate the species over time.

There are plenty of species that are toxic yet dull in coloration.  My porcupine puffer is desert camouflage color yet contains enough toxin to kill several human beings, assuming they were stupid enough to eat him.

[Sophus]

Thanks Kylyssa! Loved your input.

I'm still a little bit skeptical that it wouldn't become instinctive, however, for predators know, or have a sense, of what to avoid from the get go. Here's why...

Perhaps you are familiar with anting among birds. Basically if the first bird had begun doing this, for whatever reason, it obviously wouldn't be because of any instincts. But it has become one, as naturally much activity throughout animal behavior must. Newly born turtles know to head towards the sea. Presumably their ancestors rut it into their brain enough that now it simply happens, and it is generally "known" (more or less) by baby turtles to immediately move towards water. There are probably exceptions to every case, yet I think it's more likely for this predators to have some instincts about what to eat, just as they have some on how to attack it. Or are these typically learned as well? By all means I am eager to be proved wrong because I really don't know.