Wednesday, August 8, 2007 - 10:30 AM

COS 69-8: Effects of florivory on insect herbivors: A case study of leafminers of the blue iris

H. George Wang and Susan Mopper. University of Louisiana at Lafayette

Multi-trophic interactions are potentially important in shaping community structure. Vertebrate florivory can eliminate entire inflorescences and above-ground plant parts, which could affect the abundance and diversity of insect populations. We examined the impact of florivory on the performance of insect herbivores of the native Louisiana iris, Iris hexagona. This species reproduces sexually through seeds and clonally through rhizomes. A previous study demonstrated that vertebrate florivory increased clonal growth, with potentially positive effects on productivity and aboveground biomass. Leaves of I. hexagona are often attacked and destroyed by the leafminer Cerodontha iridiphora. We conducted a common garden experiment to test if florivory indirectly affected leafminer fitness, which would indicate a tri-trophic (florivore, plant, leafminer) interaction. We assigned irises to one of four levels of florivory (0, 1, 2, or 3 flowers removed), and recorded the subsequent density and mass of leafminer pupae. Results indicate that the highest level of florivory significantly decreased the number of leafminers. Florivory had no effect on leafminer mass. Our results suggest that despite the negative effects of florivory on iris sexual reproduction, it can benefit its overall fitness by increasing clonal growth, and reducing the density of an important natural enemy.