When the forest around them is cleared for agriculture, Amazonian trees like Dinizia excelsa are no longer within easy reach of vital pollinating insects. Effectively isolated from others of their species, these sex-starved giants live long, but reproductively empty, lives - or so it was assumed.
Christopher Dick of Harvard University closely studied the insect visitors to these so-called ‘living dead’ trees, and tracked pollen exchanges using DNA techniques. He found that, rather than being dangerously genetically isolated, trees in cleared areas spread their pollen further than those in undisturbed forest. African ‘killer’ bees, introduced in the 1970s and normally considered a harmful alien species, are responsible. Foraging over great distances, they bridge the gaps between trees that native pollinators cannot cross.