A Habitat Suitability Model for the Biocontrol Agent Mecinus Janthiniformis in Idaho

Abstract

Since the introduction of Dalmatian toadflax (Linaria dalmatica (L.) Miller) to North America in the late 1800s, it has become a costly invasive species throughout the western United States. To manage the ecological as well as economic impacts from Dalmatian toadflax invasion, a biological control program was initiated. An important biological control agent for Dalmatian toadflax, the stem-mining weevil Mecinus janthiniformis Tosevski & Caldara, was released in Canada in 1991 and the U.S. in 1996. To determine the effectiveness of biological control agents like M. janthiniformis, the Idaho State Department of Agriculture created a standardized impact monitoring protocol (SIMP). The SIMP allows land managers to take a more active role in monitoring the progress of M. janthiniformis. Therefore, I used the SIMP data collected from land managers to determine the effectiveness of M. janthiniformis at 31 sites throughout Idaho.All but one of the sites had reductions in Dalmatian toadflax, 24 of which had statistically significant reductions (P > 0.05). Sites that had effective reductions in Dalmatian toadflax densities were deemed suitable habitats for M. janthiniformis. I used environmental conditions(elevation, temperature, and aspect) at sites with suitable habitats and data from literature reviews to create a habitat suitability model for Idaho. The habitat suitability model can be used to measure the effectiveness of the biological control program in Idaho. I overlaid biological control release sites on the habitat suitability model to determine the habitat quality at the release sites. A total of 206 releases of M. janthiniformis were found, and from the results of the habitat suitability model, I deemed that 70 releases were in areas where the weevil is unlikely to establish. Many of these releases were clumped together, indicating multiple failed establishments. These results show that the creation of habitat suitability models can be an effective means to measure the effectiveness of biological control programs and provide information for implementing future programs.