PROTECTION AGAINST HERBIVORES OF THE MYRMECOPHYTE LEONARDOXA-AFRICANA(BAILL.) AUBREV. T3 BY ITS PRINCIPAL ANT INHABITANT APHOMOMYRMEX AFEREMERY

Leonardoxa africana T3 is a myrmecophyte, a plant with specialized str uctures (domatia) that shelter ants. Adult trees are essentially all o ccupied by the ant Aphomomymex afer. One tree possesses one ant colony . Ants tend homopterans inside the domatia. The plant provides ants wi th nest sites and food via production of extrafloral nectar and via ho neydew produced by homopterans. Workers patrol the young leaves, altho ugh their nectaries are not yet functional. This study was conducted t o investigate the nature of the relationship between the plant and its ants. In order to determine whether ants protect the plant against he rbivorous insects, we placed microlepidopteran larvae on young leaves of several trees, and measured the time until discovery of the larvae by the workers. We then studied the responses of workers as a function of insect size. We showed that workers patrolled the young leaves of the majority of trees. There was, however, inter-colony variability in intensify of patrolling. Workers attacked every larva they found, kil ling and eating the smaller ones, and chasing larger ones off the youn g leaf. Most of the phytophagous insects attacking young leaves of L. africana T3 were inventoried in this study. We showed that the larvae of microlepidopterans, one of the most important herbivores of this sp ecies, form parr of the diet of A. afer. The function of the stereotyp ed behaviour of ant patrolling on young leaves may be in part to obtai n insect protein to complement carbohydrate-rich nectar and honeydew, and in part to protect the host and thus increase its production of re sources for ants. Our study hows that ants protect the tree against he rbivores, and that even if this protection is less pronounced and more variable than that demonstrated for their sister species L. africana sensu stricto and Petalomyrmex phylax, the association between L. afri cana T3 and A. afer is a mutualism. ((C) Academie des sciences / Elsev ier, Paris.).