Pioneer plant protection against herbivory: Impact of different ant species (Hymenoptera : Formicidae) on a proliferation of the variegated locust

This study was conducted in order to determine the protective role of ants on Alchornea cordifolia (Mull. Arg.), a pioneer Euphorbiaceae with extraflo ral nectaries, during a proliferation of Zonocerus variegatus (L.) (Orthopt era; Pyrgomorphidae). The associated ant species recorded along river banks (typical habitat of A. cordifolia) and dirt roads (extension of the plant species area of distribution due to human activity) were basically the same , but the proportions between ant species varied. For example, ground-nesti ng, arboreal-foraging species were more frequent along dirt roads. The most efficacious ant species against attacks from the locust were those using t he supporting plant leaves to build their nests (i.e., Oecophylla longinoda [Latreille], Polyrhachis laboriosa [F. Smith], two large Formicinae, and T etramorium aculeatum [Mayr], a small, nocturnal Myrmicinae). Crematogaster striatula (Emery), another small myrmicine ant nesting at the bases of tree s, but foraging diurnally in their foliage, also protected the plant (signi ficant difference with the control lot where ants were excluded), while Cam ponotus brutus (Forel), a large nocturnal Formicinae, did not protect the p lant at all. These results are discussed according to the area of distribut ion of the plant in relation to the nesting behavior and the rhythm of acti vity of its associated ant species.