The effects of increased ant attendance and reduced herbivory on the hooded pitcher plant Sarracenia minor

Pitcher plants (Family Sarraceniaceae) are important members of wetland communities, and are unusual in that they function as both producers and consumers.  Understanding the ecology of pitcher plants is particularly important because many of the North American species in this family are threatened or endangered in at least part of their range.  In this study we used a factorial field experiment to increase ant attendance and reduce herbivory by the pitcher plant mining moth, Exyra semicrocea, on a population of the hooded pitcher plant, Sarracenia minor, in Florida.  Ant attendance was increased by installing PVC pipes (which were used as nest sites) adjacent to half of the plants and herbivory was reduced by caging half of the plants.  Reduction of herbivory through caging significantly increased the size, number, and quality of pitcher plants.  Increased ant attendance resulted in direct positive effects on pitcher plants by increasing capture rates by pitchers, but also a positive indirect effect through defense of the plants from the moth E. semicrocea.  The results of this study show that herbivory can have significant negative effects on the hooded pitcher plant, and that ants provide a double benefit by acting directly as a food source and indirectly by reducing herbivory.