The reason behind the 'Colour of Fruit' - Seeker's Thoughts

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Thursday, 4 October 2018

The reason behind the 'Colour of Fruit'

The Question- Why fruits are colorful?

This question has puzzled scientists for many years and now a team of researchers from Germany, Canada and Madagascar have a simple answer — to attract animals. 


The Connection between Color and Local seed dispersing animals
The colour of the fruit depends primarily on the visual capacity of the local seed dispersing animals. This was shown by a study published in Biology Letters that looked at the colors of fruits and the animals that disperse their seeds, in Uganda and Madagascar. 
More specifically, they did not just look at color alone, but rather at the difference between the color of fruit and leaves. In Uganda, monkeys, apes and birds are the primary seed dispersers. While Old-World monkeys and apes have a color vision similar to that of humans, birds are one step higher and can see even more colors than us.  The researchers found that fruits in Uganda take advantage of this color vision of animals, and color fruits in shades that make them stick out in the eyes of animals which can distinguish between red and green.
But in Madagascar, the main seed-dispersing animals are lemurs amongst whom most or all the animals are unfortunately red-green color blind. So, fruits and leaves have acquired shades that make them stick out to colorblind animals.
Other driving forces
To fully understand the forces driving fruit color, the authors conducted another study, which was published this week in Scientific Reports. They tested whether closely related species tend to be similar, whether abiotic factors such as solar radiation can affect fruit color and the color of the fruits dispersed by different animals. While ancestors and closely related species did not affect fruit color, abiotic factors did play a role. Though fruit and leaf color did not correlate in the visible light spectrum, they did show similarities at the UV light part of the spectrum. The fruit and the leaf reflected UV light in a similar way. This could be due to some defense system. Ultraviolet light can be harmful to both fruits and leaves, so species that defend their leaves by reflecting UV light do the same in the fruits.
The researchers also found that in both Uganda and Madagascar, fruit species that rely on bird seed dispersal tend to be redder while those which specialize on primate seed dispersal are greener. 
This may be explained by the fact that primates possess an excellent sense of smell and their heavier reliance on fruit scent means that, on an average, fruits need to invest less in visual signals.