Past Winner
2008 NSERC Doctoral Prize

Jason Weir

Zoology

The University of British Columbia

Conventional wisdom has always held that the tropics are home to a very diverse array of species because evolution takes place faster there, and because there are fewer pressures to drive species extinct. Well that's only half true, according to doctoral research done by Jason Weir at the University of British Columbia. His work has shed new light on the pressures that drive evolution, earning him an NSERC Doctoral Prize.

Dr. Weir studied a phenomenon called the "latitudinal diversity gradient," which basically means that each degree of latitude away from the equator reduces the number of species inhabiting a particular area. The phenomenon applies to virtually all organisms, from the smallest to the largest, and is more pronounced in the Americas than anywhere else in the world.

His research revealed the fact that not only does diversity shrink as you move towards the poles, but species also get younger along the way. Dramatically younger, in fact – Arctic species averaged less than a million years old, while tropical species had normally been around three to four million years old.

When two populations of a species are separated by a geographical barrier, each group experiences its own set of genetic changes. Dr. Weir looked at DNA from mitochondria – sub-cellular structures whose DNA mutates a predictable amount with each generation – in order to determine how long ago an organism began to deviate from its cousins.

The surprising results suggest that the harsher conditions and more dramatic climatic cycles away from the tropics actually speed up the process by which new species evolve. Not only do species form faster, but each stage in the evolutionary process appears to take less time. The catch is that those same harsh conditions also cause more extinctions, keeping the overall number of species low.

Dr. Weir's research challenges the existing explanations for the latitudinal diversity gradient, which include the idea that the tropics are more diverse simply because they have supported life for a longer time, or because the tropics have greater resources and can therefore support more species than high latitude regions with fewer resources.

Unfortunately, those who are trying to preserve biodiversity can draw little comfort from Dr. Weir's conclusions. Since even a fast rate of evolution is measured in tens of thousands of years, many species are unlikely to adapt quickly enough to cope with rapid changes in climate such as those observed in the Arctic in recent years.