Melaleuca quinquenervia (Cav.) Blake, an invasive tree from Australia that has spread over the freshwater ecosystems of southern Florida, is displacing native vegetation such as slash pine (Pinuselliottii), pond cypress (Taxodiumascendens), and loblolly bay (Gordonialasianthus), thus threatening native biodiversity. Suppression of melaleuca appears to be progressing through the introduction of insect species. But the long-term effects of the biocontrol remain unknown. Our objective is to understand the effect of biocontrol on the dynamics of the Melaleuca in native southern Florida plant communities. We projected likely future changes in the plant communities over the next few decades using the individual based modeling platform, JABOWA, by simulating successional processes occurring in areas of Everglades occupied by native species and melaleuca, both in the absence and presence of the biocontrol agents. JABOWA simulated plant succession in a 0.1 hectare plot, given the characteristics of a number of plants and a set of environmental conditions. Five native species; slash pine, pond cypress, dahoon holly, sweet bay and loblolly bay, were included in the model. To the best of our knowledge, no study has applied an individual-based model to simulate the effect of biocontrol on an invasive species and subsequent dynamic succession of the plant community previously affected by an invasive exotic plant.
We simulated the impact on mixed communities with melaleuca and native species in cypress- and bay-swamps. We found that it took longer for melaleuca to invade cypress swamp than bay swamp and melaleuca’s invasion led to obvious decreases of density and basal area of native species in the two swamps. Biocontrol had an effective impact on controlling melaleuca’s invasion and resulted in a recovery of native species. Biocontrol was also modeled on pure melaleuca stands and we found that it was more effective in reducing density and basal area if it was applied to melaleuca stands with larger individuals. This study supports the long-term effectiveness of biocontrol on controlling melaleuca’s invasion and suggests that JABOWA model can be applied to project effects of biocontrol, and perhaps other control methods, on other invasive species.