The May 2013 issue of Annals of Botany is now free access

A flower of Paederia
A flower of Paederia, a pantropical genus of woody lianas, together with a map of its inferred dispersal from an origin in the Oligocene in tropical continental Asia. Long-distance dispersal such as this may be much more common than previously thought and may represent an important mechanism in the assembly of modern tropical floras. See Nie et al.

The May 2013 issue of Annals of Botany is now free access. The cover image for this month is a flower that looks quite different, depending on where in the tropics you look at it. Why isn’t there a smooth variation in form as you travel round the world? Nie et al propose that the answer is because Paederia didn’t spread slowly overland.