Geographic distribution and dispersal rate of Oxyops vitiosa (Coleoptera: Curculionidae), a biological control agent of the invasive tree Melaleuca quinquenervia in south Florida

Abstract

We assess the geographic distribution and rate of spread of Oxyops vitiosa (Pascoe), a classical biological control agent of the invasive Australian tree Melaleuca quinquenervia (Cav.) S.T. Blake. This weevil has been released at 135 locations in south Florida, where it now occurs in 9 of 19 infested counties. When averaging dispersal distances among four representative sites, O. vitiosa spread at a rate of 0.99 (±0.28) km/yr, ranging from 0.10 to 2.78 km/yr. The rate of spread by O. vitiosa across melaleuca-dominated habitats was influenced by both ecological- and human-mediated parameters, including M. quinquenervia stand fragmentation (spatial separation among host plants), the number of weevils released, and time since release. The rate of spread was positively correlated with stand fragmentation level: high = 2.04, medium = 1.07, and low = 0.30 km/yr. By incorporating the dispersal rate from the highest fragmentation level into a simulation model we predicted that 138 months (June 2008) would be required for 50% of the habitat currently invaded by melaleuca to become infested at an economic weevil density (0.5 individuals per branch tip). At medium and low fragmentations, the model predicts 182 (February 2012) and 191 (November 2012) months, respectively. After examining the output from this basic model, we identified 16 possible redistribution sites that may accelerate the spread of the weevil.