Critical evolutionary leaps in plants or animals are of particular interest to scientists. The association of plants with beneficial partners, particularly insects, is one that allows for significant plant diversification. Because nectar glands evolved independently over many plant families throughout history, there has been ample opportunity to study the genetics of this trait. For example, sugary food from nectar glands attracts ants that then defend the plant and their food source from plant predators. Plant survival is increased and the energy the plant formerly spent on defense can then be directed to other traits allowing for diversification. If you have never noticed how many plants provide food for insects from sugary nectar glands, you might start looking and prepare to be fascinated.
Proceedings of the National Academy of Sciences, 2014, 111 (46)