I have broad interest in understanding the population ecology of invasive, non-native aquatic and wetland plants, and of the biological control insects used to manage them. Past research focused on describing the population dynamics of the floating aquatic weed Pistia stratiotes (waterlettuce). In the course of that investigation, we refuted the misconception that this weed did not produce seed in the U.S. and described the biology of previously unknown immature stages of the moth Petrophila drumalis. Successful establishment in Florida of the South American weevil Neohydronomus affinis resulted in dramatic reductions in waterlettuce abundances at several field sites. Laboratory studies indicated that the Asian hydrilla fly (Hydrellia pakistanae) accepts the monoecious and dioecious strains of this aquatic weed equally well, but the monoecious form suffered more severe damage. This may be because leaves were smaller on monoecious than dioecious plants. Surveys of waterhyacinth (Eichhornia crassipes) populations throughout Florida demonstrated that plant biomass is lower at sites untreated with herbicides, but harboring biological control agents, than at times prior to introduction of the biological control insects. Plants at such sites, where weevil intensities were much higher, suffered high levels of stress and showed low growth potential. Experimental manipulations showed that augmentation of existing biocontrol agent populations can be effective at preventing waterhyacinth colony expansion, but site responses are affected by other biotic and abiotic factors as well. Also, contemporaneous biocontrol agent abundances may not be indicative of their overall impacts on plant populations because biocontrol-induced stresses accumulate over time and effects linger even after agent populations have declined. Current research investigates the ecological genetics of the invasive Australian tree Melaleuca quinquenervia and examines the potential influence of genetic variation among melaleuca populations (as measured by leaf chemistry, isozymes, and RAPDs) on Australian insects imported to control melaleuca in Florida.