When is a Species not a Species?

Superficially, it's an easy question. Lions, horses, hammerhead sharks, giant tortoises, pine trees are different species.
But what REALLY divides one species from another?

In Galapagos, the giant tortoises living on different islands have at times been considered one species, and at other times, 13 (or so) different species.  

In that change of status lies the crux of the matter. Who decides? On what basis? Read the article that appeared in The Economist last week to learn more - and be prepared to ask tough questions of your naturalist guide in Galapagos.  

To read the article, click here.  
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