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Predicting Invaders and Impacts Can it be done? Lindsay Berk Papers Ricciardi, A. Predicting the impacts of an introduced species from its invasion history: an empirical approach applied to zebra mussel invasions. Freshwater Biology 48: 972-981. Byers et al. Directing research to reduce the impacts of nonindigenous species. Conservation Biology 16: 630-640. Dreissena polymorpha-case study During the past 200 years, D. polymorpha spread across Europe through canals and by boats In mid-1980s, D. polymorpha was introduced to the Great Lakes region from Europe, as larvae released with ship ballast water Since that time, zebra mussels have had negative effects on native mussels, boats, and water pipes, seriously restricting the flow of water Ricciardi 2003 http://nas.er.usgs.gov/zebra.mussel/ http://nas.er.usgs.gov/zebra.mussel/ http://www.nationalatlas.gov/zmussels1.html Can you predict the impacts of invaders? Predictions developed empirically through data synthesis If the invasion history is known, Ricciardi suggests to compare the impacts in different ecosystems where the invasion has been documented If the invasion history is not known or it is a new introduction, Ricciardi suggests predicting the invasion by comparison with functionally similar species Impacts Increase in D. polymorpha increase in density of macroinvertebrates, 2-10x Increase in D. polymorpha increase in density of amphipod crustacean, Gammarus fasciatus, a food source for several benthic fishes. Fig. 1Changes in the density of macroinvertebrates (excluding Dreissena) before and after Dreissena colonization. Points above the 1 : 1 line indicate a positive change. Strong negative impact on US native freshwater mussels of the Unionidae family, by fouling and competition Fig. 5 Proportion of freshly killed unionids as a function of the Dreissena-unionid mass ratio Questions Ricciardi asserts that even a crude model will help in invasive management and allocation of limited resources-do you agree? Could a crude model be misleading and/or worse than no model at all? “A predictive understanding of the impacts of a known invader might be attainable if the impacts are a function of quantifiable interactions between the invader and its new environment”(972) –is this really the case or the exception? Can you predict impacts by comparison with functionally similar species? Would this work for already established organisms? Could this be used as a decision tool for exotics that have not been introduced yet? What about invaders magnifying the consequences of subsequent invaders? Is the occurrence and timing of individual invasions as “unpredictable as earthquakes”? If so, can you effectively model invasives? Is it again a case by case problem? Next Steps Where do we go from here? Directing Research Byers et al. Some Directions: Prioritize what is research is needed with limited resources available Impact-which invasive will have large impact, and what controls variation of impact? Ecosystem engineers: alter ecosystem function, through which mechanisms? Better understanding of “lag phases” What population level should invasives be held at? Approaches: Experimental analyses of known invasive impacts, derive generalizations and predictions Examine invasion history, behavior is often similar for multiple invasions Ecological modelling Remote Sensing GIS Action: Biocontrol, manual eradication, herbicides, and risk assessment (costs of options) Questions What is most needed at this moment? Pick the top research question from Table 1 or ask a new one Is the future dim for native species? Should we modify our research goals to fit practical needs? Remote Sensing of Invaders Underwood, E., S. Ustin, and D. DiPietro, 2003. Mapping nonnative plants using hyperspectral imagery. Remote Sensing of Environment 86: 150-161 Used data from airborne visible/infrared imaging spectrometer (AVIRIS) to map the abundance of ice plant (Carpobrotus edulis) and jubata grass (Cortaderia jubata) on the central coast of California. Study site http://www.nps.gov/goga/parklabs/library/plantguide http://ucce.ucdavis.edu/ Study site depicted in this color infrared image. Vegetation is shown as red yet it is impossible to differentiate invasives. Study site depicted using AVIRIS imagery to detect invasive species Loose Ends? Enemy Release Hypothesis Landscape ecology of invasive spread-fragmentation Invasibility of communities-biotic resistance Allee effect Invasive traits Exotic invasives and diversity Ecosystem function Invasion genetics Biocontrol