Steamy and wet they may be, but tropical hotspots of biodiversity are not the hottest as far as evolution is concerned. It turns out that new species emerge more frequently in temperate regions than in the tropics.
Tropical zones do host a greater species diversity, but that鈥檚 because fewer species have gone extinct there, say Jason Weir and Dolph Schluter at the University of British Columbia in Vancouver. They looked at pairs of 鈥渟ister鈥� species 鈥� pairs that evolved from an immediate common ancestor 鈥� and estimated how long ago the sisters diverged from each other.
Near the equator, sister species split on average about 3.4 million years ago, whereas those in temperate regions split roughly 1.7 million years ago. In very high latitudes 鈥� above the Arctic Circle 鈥� the sister species split even more recently, with none of those reviewed separating more than a million years ago (Science, DOI: 10.1126/science.1135590).
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Dramatic climatic changes in temperate regions over the past hundreds of thousands of years may have driven evolution harder, Weir suggests.
