Effects of Ants and An Ant‐Tended Herbivore on Seed Production Of a Neotropical Herb

This study examined a complex interaction among species, focused on (1) a neotropical perennial plant, Calathea ovandensis (Marantaceae), that produces extrafloral nectar, (2) ants that visit the nectaries, (3) an ant—tended specialist herbivore, Eurybia elvina (Lepidoptera: Riodiniadae), that feeds on buds, flowers, and fruits, and (4) other herbivores of reproductive tissues. We experimentally investigated: (1) to what extent seed production was influenced by ants and herbivores, and (2) whether spatial variation in seed production was influenced by spatial variation in the ant community. The lowest seed production (x = 6) was for inflorescences with Eurybia but without ants. Highest seed production (x = 21) was for inflorescences with ants, but without Eurybia. In the presence of ants, Eurybia lowered mean seed production by 33%. In the absence of ants, Eurybia lowered mean seed production by 66%. The eight ant species differed greatly in the magnitude of their beneficial effects on seed production. Ants were not equally distributed over sites, and spatial hetrogeneity in seed production by Calathea reflected differences in ant communities among sites. We concluded that variation and interdependence of various components of plant—animal interactions are likely to result in variation in the magnitude of their beneficial or detrimental impact on plants. Such variation should be incorporated into plant demograpic models as spatially varying alternate life history paths to yield insight into the evolutionary impact of plant—animal interactions.