INVASIVE SILENE LATIFOLIA MAY BENEFIT FROM A NATIVE POLLINATING SEED PREDATOR, HADENA ECTYPA, IN NORTH AMERICA

The acquisition of new mutualists and escape from enemies are often essential for the establishment of invasive species. With its introduction to North America, Silene latifolia successfully escaped a number of generalist and specialist enemies, including the seed predator/specialist pollinator Hadena bicruris, but information regarding the acquisition of new mutualists in a community context has not been examined. We used field observations of mixed species arrays and laboratory feeding trials and compared floral scent and plant/pollinator morphological match to explore the interaction in North America of the invasive S. latifolia with the native pollinating seed predator, Hadena ectypa, in order to understand mechanisms of enemy release and mutualist facilitation underlying the successful invasion of S. latifolia. In mixed arrays, H. ectypa visited S. latifolia at a low frequency similar to the combined visitation of other non-Hadena nocturnal moth species. Differences in the floral scent profiles of S. latifolia and Silene stellata, a native coflowering congener and natural host of H. ectypa, combined with the lack of morphological match between H. ectypa and S. latifolia, likely contribute to these results. In the field study, only one H. ectypa egg was oviposited on S. latifolia, and this did not result in a successful fruit attack. Larvae feeding trials in the lab showed no initial feeding preference for pistils of either Silene species. Therefore, our study suggests that S. latifolia has escaped the cost of seed predation typically associated with visitation and oviposition by Hadena pollinators, a potential natural enemy, while taking advantage of pollination services provided by both H. ectypa and other native North American nocturnal moth pollinators.