Genetic estimates of dispersal ability in the leucaena psyllid predatorCurinus coeruleus(Coleoptera: Coccinellidae): implications for biological control

The leucaena psyllid,Heteropsylla cubanaCrawford, can devastate plantings ofLeucaena leucocephala(Leguminosae), an economically important tree species in the Pacific Islands, Southeast Asia, Australia, India, Africa, and elsewhere. The predatory beetle,Curinus coeruleusMulsant (Coleoptera: Coccinellidae), has been introduced into many of these areas from Hawaii for biological control of the psyllid. In this study, collections ofC. coeruleuswere made from 11 populations on four islands in the Hawaiian archipelago to determine population structure and estimate levels of gene flow. Over all populations, a measure of population subdivision, θ was 0.095, and the estimate ofNem, the average migration rate, was 2.4. θ values for the individual islands were 0.02, 0.12, 0.24 and 0.05 for Kauai, Hawaii, Maui, and Oahu, respectively. Estimated levels of gene flow between populations were not correlated with geographic distance, therefore isolation by distance does not appear to be an important process structuringC. coeruleuspopulations. Gene flow estimates can be used to characterize dispersal capabilities in insects or other organisms released for biological control. In this case, the inferior dispersal ability ofC. coeruleuslikely limits its rapid widespread establishment during release programmes.