In the understory of pristine Guianese forests, the myrmecophyte Hirtella physophora almost exclusively shelters colonies of the plant-ant Allomerus decemarticulatus in its leaf pouches. We experimentally tested three nonmutually exclusive hypotheses concerning phenomena that can determine the species specificity of this association throughout the foundation stage of the colonies: (1) interspecific competition results in the overwhelming presence of A. decemarticulatus queens or incipient colonies; (2) exclusion filters prevent other ant species from entering the leaf pouches; and (3) host-recognition influences the choice of founding queens, especially A. decemarticulatus. Neither interspecific competition, nor the purported exclusion filters that we examined play a major role in maintaining the specificity of this association. Unexpectedly, the plant trichomes lining the domatia appear to serve as construction material during claustral foundation rather than as a filter. Finally, A. decemarticulatus queens are able to identify their host plant from a distance through chemical and/or visual cues, which is rarely demonstrated in studies on obligatory ant-plant associations. We discuss the possibility that this specific host-recognition ability could participate in shaping a compartmentalized plant-ant community where direct competition between ant symbionts is limited.

Cordia nodosa Lamark (Boraginaceae) is a myrmecophyte (i.e., plants housing ants in hollow structures) that provisions associated ants with food bodies (FBs) produced 24 h a day. Distributed over all the young parts of the plants, they induce ants to forage continually and so to protect the plants. Metabolites are stored in the inner cells of C. nodosa FBs as they form. In addition the peripheral cells have an extrafloral nectary-like function and secrete a substance that covers the FBs. The amalgam of these two functions, distinct in other known cases, is discussed taking into account the origin of FBs and extrafloral nectaries.

Resume.-Cecropia obtusa Trecul est un myrmecophyte associe dans une relation stricte avec les fourmis Azteca (A. alfari Emery et A. traili Emery). Ces dernieres occupent les entre-nceuds de l'arbre et se nourrissent des corps nourriciers ou corps de Muller, corpuscules pluricellulaires produits a Ia base du petiole de chaque feuille fonctionnelle a partir d'un tissu particulier, le trichilium. L'activite de production des corps mulleriens est liee a celle des fourmis et se situe dans les trois heures precedant Ia fin du jour. Une chenille Phycitinae peut egalement occuper le Cecropia et consommer exclusivement les corps nourriciers landis qu'un champignon Fusarium moniliforme parasite le trichilium en !'absence des fourmis. La distribution de Cecropia obtusa, espece pionniere, est homogene dans l'espace et dans le temps, mais sa dynamique de croissance est sous controle des facteurs topographiques, edaphiques et climatiques. La comparaison entre les individus occupes par les fourmis et ceux qui ne le son! pas montre que ces derniers se developpent moins vile et produisent moins de corps nourriciers. Le comportement des Cecropia cultives en serre rejoin! celui des individus inoccupes du milieu naturel avec cependant une production plus elevee de corps nourriciers. Lorsque les chenilles occupent Ia plante, le nombre des corps nourriciers produits est plus grand que celui des individus inoccupes. Le role des fourmis et des chenilles dans Ia dynamique de developpement et Ia production des corps nourriciers est discute. L'analyse chimique partielle du corps nourricier montre une nette dominance du glycogene auquel s'ajoutent des sucres simples, des lipides, des proteines et Ia presence des vitamines C et E. Les differences constatees entre Ia composition des corps mulleriens du milieu naturel et celle des corps nourriciers produits en serre sont discutees. L'examen histologique et cytologique du corps de Muller a permis de mettre en evidence son ontogenese et l'origine des principales substances synthetisees ayant un role trophique pour les fourmis et les chenilles. SummmJ 1 .-Cecropia obtusaTrecul is a myrmecophytic plant associated in a strict relation with the ants Azteca (A. alfari Emery and A. traili Emery). The ants inhabit the internodes of the tree and feed on nutritive bodies or mullerian bodies. These multicellular corpuscles are produced on the abaxial face of the base of the petiole. This region is covered with a velutinous mat of multicellular but uniseried trichomes called trichilium. The production activity of mullerian 290 bodies and the activity of the ants are synchronous: three hours before the sundown. A Phycitinae caterpillar may occupy the Cecropia internodes and consumes mullerian bodies exclusively. A fungus, Fusarium moniliforme, grows on the trichilium in the absence of ants. The distribution of Cecropia obtusa is homogeneous in space and time but its growth is under control of topographic, edaphic and climatic factors. The comparison between trees occupied by ants and inoccupied ones shows ...