Invasion of American native lily populations by an alien beetle

The lily leaf beetle (Lilioceris lilii), indigenous to Eurasia, was first detected in North America on the island of Montréal, Québec, Canada in 1943. Populations remained limited to the original site of introduction but since 1978 the distribution of this species has expanded in all directions. To date L. lilii has only been recorded feeding on cultivated lilies in urban and rural areas. But as the beetle spreads its geographic range it could encounter native lily species. The objectives of this study were to determine the suitability of two indigenous North American lily species (Lilium canadense and L. philadelphicum) as host for L. lilii, and to assess the degree of infestation of wild lily populations. Measurement of fitness parameters under laboratory conditions (survival, development time, size) indicated that L. lilii has the capacity to develop on both species of native lilies. In the provinces of Québec and Ontario eight of the 20 wild populations of L. canadense sampled were infested. In contrast, L. philadelphicum was not attacked by the alien beetle. A number of native lilies are already endangered in North America, so there is an urgent necessity to address the ecological impact of L. lilii in natural ecosystems.