13 July 2011

Darwin's orchid and moth and the fascinating world of evolution

Darwin's theory of evolution has always intrigued me. I remember when I first read it in high-school, it looked so intuitive and obvious that I questioned the need of even spelling it out. Little did I know then of the prodigious implications of that simple hypothesis.

Recently while watching a TED video, I came across this fascinating story of Darwin's orchid and the moth which presents a intriguing insight into how nature has uniquely evolved over the years.

So the picture on the left is of Angraecum sesquipedale, commonly known as the Darwin's orchid. When Darwin first saw this flower, he was surprised by one defining characteristic of this species - the astonishing length of the whip-like green spur containing the nectar in each flower.

From his observations, Darwin surmised in 1862 that in order for this flower to pollinate and survive, there must be a pollinator insect with a proboscis (tubular nectar sucking organ of insects) long enough to reach the nectar at the end of the spur.


Obviously the the notion of a pollinator with a 35 cm long proboscis was ridiculed and generally not believed to exist for the longest time. Though all of this was about to change 41 years later.

In 1903, such a moth was indeed discovered in Madagascar - just like Darwin had predicted. Named Xanthopan morganii praedicta (The subspecific epithet "praedicta" was given in honor of the fact that Darwin predicted its existence), this moth had a long proboscis which it kept rolled up and unrolled to reach the end of the orchid's spur. The fact that Darwin was able to apply his simple theory to predict an actual species 41 years ago since it was first seen is the reason why evolution remains to be one of the most profound science theories of all time.

Don't take my word for it? Watch it here for yourself in this short BBC documentary.


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