The Biologian: mimicry

Seed question that propagated this blog: Why are some skink tails blue?

Then, the questions kept rolling in:

Why is blue a relatively rare color in nature? Is it actually rare? What percentage of different clades like flowers, reptiles, birds, etc. are blue?
Is blue the anti-red/orange?
Could it actually be to attract predators to its tail (so as to distract from its body/head) much like false eye spots/false heads?
Does it serve a mating purpose?
Why do some of the same species of skink have red or pink tails?
Does the skink's tail detach? Would a predator attacking its tail as opposed to its body actually make it more likely to survive?
Is sight an important sense for the important predators of the skink? What are the main predators? Is there variation in coloration in areas that have more of a certain kind of predator?
Are the pigments that create blue difficult to evolve or metabolically costly to make?

Hypothesis Number One: Blue is the anti-red/orange. Meaning it functions as the opposite of a warning color.

You may be well aware that many species use the bright red/orange coloration to advertise themselves as poisonous, venomous or foully flavored. It's literally a bold move, but for many, many organisms it's a great way to avoid getting eaten.

So, why on earth would you do the opposite of that warning coloration and essentially advertise that you're edible? It seems suicidal, but there may be strategy in it yet. First, consider some other animals that do something sort of similar:

False Eye Spots (so a predator goes toward the end that you're best at getting away from and that is the least vital to survival):

False head Tails:

I've even seen video where this guy (or perhaps a similar species) will move their wings up and down to create a motion with the false antennae that is picture perfect of the real deal.

How we could test to see what the purpose of the tail really is:

Paint the tails other colors such as red or the normal color of the skinks body and observe

Differentiation of mating success
Differentiation of death by predation

Find out predator distribution and abundance in areas that have color variations such as red or pink.
Test the break-ability of the tail during predator attacks to see if attracting predators toward tail and away from body/head is actually effective or not.
Count the number of broken/attacked tails in a normal population in comparison to comparable lizard species to in comparison to skinks with variant tail colorations to determine if the tails does in fact serve as a escape mechanism.

Second hypothesis: Blue is the anti-red/orange for mating displays. Blue is dangerous since it is the opposite of a warning coloration and therefore red would more likely be used first, but once red/orange is taken subsequent species will want to contrast themselves to avoid inbreeding and watering down their evolved adaptations.

Is it just coincidence that blue footed boobies and the red decorated frigate bird nest on the same islands?

How we could test it:

See if there areas that have blue species but no red species
Count and establish the coloration break down as percentages
In areas that there is variation or even reversal of coloration establish population sizes of both contrast species as well as the significance of predation.
Genetically trace the age of species and see if blue species or red species split first from a common ancestor.

Their hypothesis: Blue is the anti-red/orange for displays in flowers.

Same as above.

Hypothesis Meltdowns?

Images are from here, here, here, here, here, here, here, here, here, here, here, here, here, here and here.

It's hard not to make the comparison to high school. Cliques most definitely have ways of 'being different just like everyone else' - goth, prep, grunge, rock, American Eagle, hip hop, gangsta, etc. Organisms do this, too, and the how and why I find intriguing.

Have you ever looked in a bird identification book (maybe that's asking too much) and thought, sheesh there sure are a lot of not just species but different looking birds? Reds, yellows, greens, browns, blacks, whites, oranges, plumes, streaks, spots, dots, crests, ridges...The shapes and shades are endless. Why? Well, one reason you're probably familiar with - males like to strut their stuff. You got to look good if you want to get the date. Dress to impress.

But, there's more. Say you have a bird's brain, i.e. you're a bird brain, how do you easily tell one species from another to know if you can/should mate with them? Like in the jungle of a high school cafeteria, animals need to know where they fit in.

What's at stake if you make a mistake and mate with another species? Well, let's take one classic example - the Darwin finches of the Galapagos islands. Different islands have different foods. Different beaks are good at different foods. Therefore, different islands evolve birds with different beaks, each optimized for its diet, be it seeds, insects or cacti. Spear like is great for insects, plier like is great for cacti and nut cracker like, unsurprisingly, is good for nuts.

Important: each beak is relatively optimized and any deviation from that is a disadvantage (usually speaking). So, any hybrid cross breading would only take the evolution of that bird down a blind alley that would hurt and not benefit the long term prospects of that species.

So, how to guard against that?

Species have evolved ways to prevent unevolution. Make yourself different. Special. Unique. Outstanding. Cliquish. Mark your kind as different from others.

In the case of Darwin finches, sound different. Below is a graph from this article that shows the different species unique vocalizations.

Next example: cichlids.

These cute little African fishies come in a kaleidescope of hues. Experiments have been done to demonstrate this rainbow of colors isn't just for the pet trade, but is an ingrained programing and color coding system to keep it within the family so to speak (conspecific mating). Why? Remember, to hold on to advantageous adaptations and not have them watered down.

Don't think this is limited to visual cues. Olfaction is a big player for insects (like butterflies that can often be similarly colored - especially in mimicry where non-poisonous species try to look like poisonous species like the Monarch and Viceroy butterflies) and cave dwelling fish (even some cichlids!) and the visually easy to confuse Coral and Milk snakes (also mimicry).

There is another side of the coin. It's common knowledge that inbreeding can fix diseases and mutations in a population. It, like everything, needs to be a balance. Too much of a good thing gets nasty.

Example 1 of this: humans! Social taboos keep us from mating with our siblings and relatives. It's also been shown that we tend to not find the smells of close relatives sexually attractive.

Example 2: petunias (click on for article).

These cute, common garden plants have molecular markers (antigens) attached their their pollen that make it possible to distinguish their own pollen from that of another petunias. Because they want genetically diverse offspring they have evolved ways to give preferential treatment and position the foreign pollen to the front of the fertilization line.

It's an interesting thought to think about how these two forces play an evolutionary tug-of-war within species. Species both want to maintain their identity and specific adaptations as well as maintain genetic diversity to avoid genetic stagnation and inbreeding.

Maybe this is why some birds continue to acquire new displays. Maybe elaborate displays like plumage aren't just the handicap principle. Maybe it's females constantly trying to make sure their little youngins have fresh genes. Take for example the Mandarin duck, the craziest duck you've ever seen (Please take your time examining the detail in the plumage. Truly an evolutionary marvel). They don't just have one really spectacular feature. They have dozens. Each display being maintained to distinguish from other species, but added to in order to show genetic diversity to potential mates.

You might think of it like a bullseye. The female is the center of the bullseye and doesn't want to mate with males also in the center, i.e. very close to here genetically, nor males hardly related to her at all. It's the in between sweet spot that evolution seems to shoot for (unintended pun).