Ant–plant interactions: the importance of extrafloral nectaries versus hemipteran honeydew on plant defense against herbivores

Abstract

The two most important ant–plant attractions are extrafloral nectaries (EFNs) and hemipteran honeydew. In both cases, ants may offer an effective protection against natural enemies of plants, in exchange for its sugar-rich exudates. The aim of this paper was to compare the efficiency of ant protection between plants with EFNs and with hemipteran honeydew. The study was carried out in the Amazonian Rain Forest Reserve at km 41 (02º 24′S, 59º 44′W), located 80 km from Manaus. We recorded 24 ant species in 25 plants species in the forest understory along two line transects of 5 km. The efficiency of ants in protecting plants was measured by an experiment of prey removal using isopteran workers. It was found that ants are more effective and faster in attacking termites when using honeydew rather than EFNs, probably due to the larger resource monopolization. This study further underlines the importance of experimental studies to elucidate the ecological and evolutionary importance of EFNs and honeydew in ant–plant defense against herbivores.