Magazine article Geographical

Darwin's Puddle: Blue and Yellow Fish Living in a Small Lake in Tanzania Are Helping Scientists Understand Basic Mechanics of Evolution

Magazine article Geographical

Darwin's Puddle: Blue and Yellow Fish Living in a Small Lake in Tanzania Are Helping Scientists Understand Basic Mechanics of Evolution

Article excerpt

Speciation is the slow break of a single species into two. Geographical barriers are thought to be the main drive of these splits, when rivers, seas and mountain ranges prevent the genes from intermixing any further than they already have. Take the Asiatic and American black bear for instance--though they share a common ancestor, the two species have become genetically distinct on their respective continents.

But what happens when the geographical location is entirely contained? In a small volcanic lake in Tanzania, what was once a single species of cichlid fish is slowly becoming two, a process known as sympatric speciation. While similar phenomena have been noticed in Lake Malawi--dubbed 'Darwin's Pond'--where more than 875 cichlid species have evolved from just a handful of ancestors, it is the far smaller Lake Masoko--nicknamed 'Darwin's Puddle' - that the secrets of sympatric speciation are beginning to be realised. At just 700 metres wide, it is a mystery how the pond's fish can possibly separate their gene pools. Yet that is precisely what is happening.

"The two cichlids now have different features,' says George Turner, a biologist at the University of Bangor who has been studying their genetics. 'They have different colours, habitat preferences, behaviour, diet and morphology. …

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