Protect and survive

摘要

The symbiosis between bullhorn acacias and Pseudomyrmex ferruginea, the bullhorn acacia ant, is the stuff of biological legend. The acacias provide the ants with food, in the form of protein, fat and sugar secreted for their delectation by special organs called Beltian bodies, and also with homes, in the hollow thorns which give the plant its name. The ants reciprocate by stinging anything-from other insects to cattle-that dares try to eat the acacia's leaves. The latest research, though, suggests that the ants do more than just drive away herbivores. They also act as a sort of immune system which protects acacias from infection. This discovery, reported in New Phyto-logist by Marcia Gonzalez-Teuber of La Serena University, in Chile, dates back to an observation made a decade ago that maca-ranga trees, which have similar symbiotic relations with ants, seem immune to a particular fungus when ants are present, but not when they aren't. Dr Gonzalez-Teuber wondered if something like this was true of acacias-and if it was, why.