The Evolution of Weeds

I don't know about you but the way nature adapts to mankind never ceases to amaze me. Of course the general public can get a bit ratty about Squirrels on the feeder or a fox raiding the dustbin but you have to admire them, well I do.

For example the daisy like annual weed Crepis sancta has two types of seed, one is big and heavy and drops straight down and the other is light and floats on the wind. Apparently the weeds growing in patches of soil around trees in the French city of Montpellier have evolved over a period of just 12 years to produce more of the big seeds than the flighty far-reaching ones. Well that is according to research by Pierre-Olivier Cheptou from the CNRS.

M. Cheptou first noticed the trend in an urban environment. To find out whether it was due to a genetic change, instead of environmental factors, he took seeds from both rural and urban environments and grew them in a greenhouse. The two plant types were allowed to be pollinated only by similar plants, and once they flowered, the different types of seeds were collected and counted.

M Cheptou and his team found that the urban plants grew a higher percentage of heavy seeds. It also found that light seeds had less chance of floating to acceptable habitat in urban locales. However this adaption could cause problems, if the environment changes rapidly, locally well-adapted populations may go to local extinction and disappear. The plant may eventually lose the ability to spread itself.

Apparently similar trends have been seem with isolated ocean island plants where heavier seeds don't get blown out to sea.