Modeling the long-term effects of introduced herbivores on the spread of an invasive tree

Authors: ZHANG, BO - University Of Miami; DEANGELIS, DONALD - Us Geological Survey (USGS); Rayamajhi, Min; BOTKIN, DANIEL - University Of California

Submitted to: Landscape Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2017
Publication Date: 4/17/2017
Citation: Zhang, B., Deangelis, D., Rayamajhi, M.B., Botkin, D. 2017. Modeling the long-term effects of introduced herbivores on the spread of an invasive tree. Landscape Ecology. 32(6):1147–1161. http://dx.doi.org/10.1007/s10980-017-0519-6.
DOI: https://doi.org/10.1007/s10980-017-0519-6

Interpretive Summary: Melaleuca is an invasive tree of Australian origin that has spread over a vast area of the freshwater ecosystems of southern Florida. It has displaced native vegetation and threatened native biodiversity. Suppression of the populations of this invasive appeared to progress following the introduction of biological control insects (weevil and psyllid). However, the long-term effects of herbivory on melaleuca infestations remains unknown. We projected possible changes in the plant communities over the next few centuries by using the individual based modeling platform, JABOWA-II. By using this model we simulated successional processes occurring in two types of Everglades habitat occupied by native species and melaleuca, both in the absence and presence of the insect herbivores. Five native species; slash pine, pond cypress, dahoon holly, sweet bay and loblolly bay were included in the model. Computer simulations showed that melaleuca invasion leads to a decrease in the density and basal area of native species, but the expected level of herbivory would check further increase of melaleuca infestation and ultimately result in the recovery of native species. When herbivory was modeled on pure melaleuca stands, it was more effective in reducing density and basal area when applied to the melaleuca stands with initially larger individuals. Although the simulated herbivory did not predict an elimination of melaleuca, it indicated a dramatic density decrease in all cases, supporting the assumption of the long-term effectiveness of herbivory on melaleuca's invasion potential.

Technical Abstract: Melaleuca quinquenervia (Cav.) Blake (hereafter melaleuca) is an invasive tree from Australia that has spread over the freshwater ecosystems of southern Florida, displacing native vegetation such as slash pine (Pinus elliottii), pond cypress (Taxodium ascendens), and loblolly bay (Gordonia lasianthus), thus threatening native biodiversity. Suppression of melaleuca appears to be progressing through the introduction of insect species that feed on the melaleuca, including the melaleuca weevil Oxyops vitiosa Pascoe and the psyllid Boreioglycaspis melaleucae Moore. But the long-term effects of the herbivory remain unknown. Our objective is to improve our understanding of the possible effects of this herbivory 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 centuries using the individual based modeling platform, JABOWA-II, by simulating successional processes occurring in two types of Everglades habitat occupied by native species and melaleuca, both in the absence and presence of the insect herbivores. Five native species; slash pine, pond cypress, dahoon holly, sweet bay and loblolly bay, were included in the model. Computer simulations show melaleuca invasion leads to decreases in density and basal area of native species in the two swamps,. but that expected level of herbivory would effectively control melaleuca invasion, resulting in a recovery of native species. When herbivory was modeled on pure melaleuca stands, it was more effective in reducing density and basal area when applied to melaleuca stands with initially larger individuals. Although the simulated herbivory did not eliminate melaleuca, it decreased its presence dramatically in all cases, supporting the long-term effectiveness of herbivory by introduced insects on controlling melaleuca invasion.