The pollinator crisis: What's best for bees

Pollinating insects are in crisis. Understanding bees' relationships with introduced species could help.
Harmon-Threatt is one of a growing group of scientists studying the evolving relationships between native bees and introduced plants. Their work is critical in a world where human actions have dramatically shifted the distributions of plants and are forcing a pollinator crisis. Most flowering plants need animal pollinators in order to reproduce, and bees serve that role for many important crops — including fruits, pulses, some vegetables and alfalfa — many of which were themselves introduced to the United States.

http://www.nature.com/news/2011/111109/full/479164a.html