Spatial dynamics of dalmatian toadflax (Linaria dalmatica) and attack by the stem-mining weevil Mecinus janthinus

Changes in the number, distribution and size of plant stands generate a dynamic spatial pattern with important implications for the spatial and temporal dynamics of specialist herbivores using these plants as a host. For example, the spatial arrangement and quality of plant hosts largely affects host finding behavior and population persistence of many herbivorous insects. The stem-mining weevil Mecinus janthinus Germar was introduced into North America in the mid 1990s as a biological control agent of the herbaceous perennial Dalmatian toadflax (Linaria dalmatica (L.) P. Mill.). Studies have mainly focused on evaluating impact of M. janthinus on Dalmatian toadflax stem density and reproduction with less emphasis placed on assessing how the spatial structure of Dalmatian toadflax affects weevil attack and population persistence. It is possible that the spatial patterning of patches may be one explanation for variable population growth and impact by M. janthinus across the Pacific Northwest. This study was initiated to evaluate local spatio-temporal dynamics of Dalmatian toadflax and its affect on attack by M. janthinus at four sites across the northwestern US (ID, WA, and OR). This presentation will summarize two years of observations describing how variation in local spatial structure of Dalmatian toadflax affects weevil attack and population persistence.