Tropical Colors: Brightness & Possible Reasons

[Bartholomew]

The colors of things in tropical areas tend to be bright compared to colors in the rest of the world. Consider pineapples, avocados, kiwis, fish, and coral reefs. Why is this? Possible reasons?

 

[matthyaouw]

It is a bit of a generalisation to say that tropical = colourful, but I see your point.

What springs to mind is natural selection and predation. As a general rule, a bright coloured animal will be more easily spotted by predators and have a much greater chance of being killed before it can pass on its genetic information, meaning the genes coding for its bright colour die with it. If the creature has few natural predators, it can be less camoflaged and still posess a reasonable chance of surviving to mate, so the population that has brighter colours is able to increase.

Another factor is sexual selection- A number of bird species are known to pick mates by the quality and colour of their plumage (which could reflect good health in a mate), for example the peacock. A brighter coloured male would stand a better chance of mating and passing on its genes, despite the increased risk of predation.

Some species are said to be brightly coloured as a warning, and bright colours are often found on poisonous animals (like the coral snake, some poisonous frogs, or wasps) and predators learn from experience that these particular colour schemes are to be avoided. Some none poisonous animals take advantage of this too, for example there is a snake that looks extremely similar to the deadly coral snake (I'm not sure but it may be the corn snake, or the milk snake), and its colour scheme is believed to be an adaption to make it seem like a venomous snake so predators avoid it.

In terms of plants (fruits, flowers), colours can be a means for reproduction. Plants that have colourful flowers often attract insects, which pollenate the flowers as they move from one to another. Some plants have colourful fruits to make them more attractive so that they are eaten, meaning that animals spread the seeds far away from the parent plant, decreasing competition for space, light and nutrients when the seed begins to grow.

 

[DocToxyn]

I'm sitting here in the middle of a very gray and dreary, upstate NY day and even though many examples come to mind to refute Bartholomew's statement, I'm inclined to agree with that generalization today. Here are a few of my thoughts.
Species diversity in general increases as one goes from the poles to the equator, so in order to stand out in terms of species recognition and finding a mate perhaps more color variation is required in places with many different species.
On a similar idea, but going the other way, if plant diversity is lowered and the most common plant colors are browns and greens then animals associated with those plants and trying to hide from predators should replicate those colors in themselves thus the plants drive the adoption of typical camouflage colors.
Finally in marine fish and corals, sunlight gets filtered significantly as one goes down the water column so colors need to be very saturated and contrasty to be useful.
matthyaouw-the most commonly associated coral snake mimic is the scarlet kingsnake, but several other species also display some mimicry of this venomous species.
Also check out this article on aposematism and diet specialization in poison dart frogs. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=240697