I’ve written about my love of urban wildlife before, but this French weed is taking it to a whole new level. In the latest edition of PNAS, French scientists report that a humble sidewalk week has actually changed its reproductive strategy in just a few generations in order thrive amidst the vast concrete plains.
Crepis sancta is a weed with pretty yellow flowers that grows in little patches along roadsides and sidewalks. It has two types of seed: a fluffy one that can float far away, and a heavy one that stays right next to mommy. In the wild, Crepis would want to split its reproductive effort in order to both colonize new patches with the fluffy windblown seeds and to maintains its population with the heavy falling seeds.
But, of course, the wild has soil every which way, and the city does not. Fluffy seeds that land on concrete are dead. In fact, the French scientists found that fluffy seeds in the city have success rates 50% lower than fluffy seeds in the wild.
What’s a savvy urban plant to do? Make more heavy seeds, of course. Urban Crepis do indeed have significantly more heavy seeds than rural Crepis – and it’s managed to evolve this change in only 5-12 generations. In evolutionary time, that’s a New York minute. Next thing you know, Crepis will be ordering takeout and dancing till the sun comes up.
(Note that it’s my very first time officially Blogging on Peer Reviewed Research! Go to Research Blogging for more researchy goodness.)
Cheptou, P., Carrue, O., Rouifed, S., Cantarel, A. (2008). Rapid evolution of seed dispersal in an urban environment in the weed Crepis sancta. Proceedings of the National Academy of Sciences, 105(10), 3796-3799. DOI: 10.1073/pnas.0708446105