1. How organisms locate their hosts is of fundamental importance in a variety of basic and applied ecological fields, including population dynamics, invasive species management and biological control. However, tracking movement of small organisms, such as insects, poses significant logistical challenges. 2. Mass-release and individualmarkrecapture techniques were combined in an individually markmass releaseresight (IMMRR) approach to track the movement of over 2000 adult insects in an economically important plantherbivore system. Despite its widespread use for the biological control of the invasive thistle Carduus nutans, the host-finding behaviour of the thistle head weevil Rhinocyllus conicus has not previously been studied. Insects were released at different distances from a mosaic of artificially created host patches with different areas and number of plants to assess the ecological determinants of patch finding. 3. The study was able to characterize the within-season dispersal abilities and between-patch movement patterns of R. conicus. Weevils found host plant patches over 900 m away. Large patches, with tall plants, situated close to the nearest release point had the highest first R. conicus resights. Patch area and plant density had no effect on the number of weevils resighted per plant; however, R. conicus individuals were more likely to disperse out of small patches and into large patches. 4. By understanding how R. conicus locates host patches of C. nutans, management activities for the control of this invasive thistle can be better informed. A deeper mechanistic understanding of host location will also improve prediction of coupled plantherbivore spatial dynamics in general.
MIDAS Coordination Center
University of Pittsburgh
A737 Public Health
130 DeSoto Street
Pittsburgh PA 15261