An asymmetrical relationship between an arboreal ponerine ant and a trash-basket epiphyte (Araceae)

Abstract

The relationship between ants and Philodendron insigne, a trash-basket epiphyte abundant along streams, was studied in French Guiana. Only a few (3%) of the young plants sheltered ants, whereas 90% of the mature individuals did. The most frequent associate was Odontomachus hastatus (Fabricius), an arboreal ponerine ant, and its nests were almost entirely (94.4%) located in P. insigne root clusters. Experimental choice tests conducted on O. hastatus workers confirmed their preference for P. insigne. We propose that the interactions between P. insigne and ants may be intermediate between non-obligatory, reward-based interactions and obligatory, specific ant-myrmecophyte interactions because (1) almost all mature P. insigne individuals are associated with ants; (2) O. hastatus is the most frequent when diverse ants nest in its root clusters; (3) ants colonize mature P. insigne, but rarely young individuals; (4) ants, particularly O. hastatus, protect the foliage of their host; and (5) at least one ant species, O. hastatus, prefers P. insigne over other host plants. The latter relationship is asymmetrical because P. insigne is inhabited by diverse ants whereas O. hastatus nests almost exclusively in P. insigne. © 2007 The Linnean Society of London.