EFFECTS OF FLORIVORY ON THE POLLINATION OF FLOWERS: AN EXPERIMENTAL FIELD STUDY WITH A PERENNIAL PLANT

Plants experience damage to both their vegetative and their reproductive parts. Loss of leaf area can affect subsequent photosynthesis and resources available for growth and reproduction; damage to flowers can result in loss of ovules and seeds by consumption, but herbivory may also disfigure flowers, interfering with their functions of attracting and rewarding pollinators. We examined natural populations of the butterfly pea, Centrosema virginianum, in pine rockland habitat in Everglades National Park (intact habitat) and a pine rockland fragment in suburban Miami-Dade County to answer the following questions: (1) What is the breeding system of C. virginianum? (2) What are the pollinators of this species in southern Florida pine rocklands? And (3) how are flower herbivores affecting pollinator visitation and subsequent fruit set? Controlled hand-pollination experiments revealed this species to be self-compatible but requiring visitation/pollination for fruit set. Cross-pollinated flowers and open-pollinated flowers set substantially more seed per fruit than did self-pollinated flowers. Flowers are visited by a variety of bees (Bombus pensylvanicus, Xylocopa micans, Megachile spp., and Melissodes spp.), which serve as pollinators. Flowers were produced abundantly in areas that had experienced recent fires, and roughly half of the flowers were damaged by one of two florivore guilds (blister beetles that ate the flowers and petal-sucking flies in the family Agromyzidae). Damaged flowers were visited much less frequently by pollinators than were undamaged flowers, and, consequently, they set many fewer fruit and much less seed. We conclude that florivory is a major impediment to successful pollination and plant sexual reproduction of C. virginianum in areas where the species naturally occurs.