Suppression of the invasive plant Salvinia molesta by the salvinia weevil is an iconic example of successful biological control. However, in the billabongs (oxbow lakes) of Kakadu National Park, Australia, control is fitful and incomplete. By fitting a process-based nonlinear model to thirteen-year data sets from four billabongs, here we show that incomplete control can be explained by alternative stable states1,2,3,4—one state in which salvinia is suppressed and the other in which salvinia escapes weevil control. The shifts between states are associated with annual flooding events. In some years, high water flow reduces weevil populations, allowing the shift from a controlled to an uncontrolled state; in other years, benign conditions for weevils promote the return shift to the controlled state. In most described ecological examples, transitions between alternative stable states are relatively rare, facilitated by slow-moving environmental changes, such as accumulated nutrient loading or climate change5,6. The billabongs of Kakadu give a different manifestation of alternative stable states that generate complex and seemingly unpredictable dynamics. Because shifts between alternative stable states are stochastic, they present a potential management strategy to maximize effective biological control: when the domain of attraction to the state of salvinia control is approached, augmentation of the weevil population or reduction of the salvinia biomass may allow the lower state to trap the system.
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Scheffer, M., Carpenter, S., Foley, J. A., Folke, C. & Walker, B. Catastrophic shifts in ecosystems. Nature 413, 591–596 (2001)
Holling, C. S. Resilience and stability of ecological systems. Annu. Rev. Ecol. Syst. 4, 1–23 (1973)
May, R. M. Thresholds and breakpoints in ecosystems with a multiplicity of stable states. Nature 269, 471–477 (1977)
Sutherland, J. P. Multiple stable points in natural communities. Am. Nat. 108, 859–873 (1974)
Folke, C. et al. Regime shifts, resilience, and biodiversity in ecosystem management. Annu. Rev. Ecol. Evol. Syst. 35, 557–581 (2004)
Van Geest, G. J., Coops, H., Scheffer, M. & van Nes, E. H. Long transients near the ghost of a stable state in eutrophic shallow lakes with fluctuating water levels. Ecosystems 10, 36–46 (2007)
Scheffer, M. & Carpenter, S. R. Catastrophic regime shifts in ecosystems: linking theory to observation. Trends Ecol. Evol. 18, 648–656 (2003)
Scheffer, M. Critical Transitions in Nature and Society (Princeton Univ. Press, 2009)
Schröder, A., Persson, L. & De Roos, A. M. Direct experimental evidence for alternative stable states: a review. Oikos 110, 3–19 (2005)
Scheffer, M. et al. Early-warning signals for critical transitions. Nature 461, 53–59 (2009)
Carpenter, S. R., Brock, W. A., Cole, J. J., Kitchell, J. F. & Pace, M. L. Leading indicators of trophic cascades. Ecol. Lett. 11, 128–138 (2008)
Suding, K. N., Gross, K. L. & Houseman, G. R. Alternative states and positive feedbacks in restoration ecology. Trends Ecol. Evol. 19, 46–53 (2004)
Beisner, B. E., Haydon, D. T. & Cuddington, K. Alternative stable states in ecology. Front. Ecol. Environ 1, 376–382 (2003)
Room, P. M. Ecology of a simple plant-herbivore system: biological control of Salvinia . Trends Ecol. Evol. 5, 74–79 (1990)
Room, P. M. & Thomas, P. A. Population growth of the floating weed Salvinia molesta: field observations and a global model based on temperature and nitrogen. J. Appl. Ecol. 23, 1013–1028 (1986)
Finlayson, C. M. Growth rates of Salvinia molesta in Lake Moondarra, Mount Isa, Australia. Aquat. Bot. 18, 257–262 (1984)
Julien, M. H., Hill, M. P. & Tipping, P. W. in Biological Control of Weeds (eds Muniappan, R., Reddy, G. V. P. & Raman, A. ) 378–407 (Cambridge Univ. Press, 2009)
Storrs, M. J. & Julien, M. H. in Northern Landscapes Occasional Papers Vol. 1 (Australian Nature Conservation Agency, 1996)
Room, P. M. & Thomas, P. A. Nitrogen, phosphorus and potassium in Salvinia molesta Mitchell in the field: effects of weather, insect damage, fertilizers and age. Aquat. Biol. 24, 213–232 (1986)
Scheffer, M., van Nes, E. H., Holmgren, M. & Hughes, T. Pulse-driven loss of top-down control: the critical-rate hypothesis. Ecosystems 11, 226–237 (2008)
Knowlton, N. Thresholds and multiple stable states in coral-reef community dynamics. Am. Zool. 32, 674–682 (1992)
Schmitz, O. J., Kalies, E. L. & Booth, M. G. Alternative dynamic regimes and trophic control of plant succession. Ecosystems 9, 659–672 (2006)
Hastings, A. Transients: the key to long-term ecological understanding? Trends Ecol. Evol. 19, 39–45 (2004)
Strogatz, S. H. Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering (Perseus, 1994)
Holmgren, M. & Scheffer, M. El Niño as a window of opportunity for the restoration of degraded arid ecosystems. Ecosystems 4, 151–159 (2001)
Holmgren, M. et al. Extreme climatic events shape arid and semiarid ecosystems. Front. Ecol. Environ 4, 87–95 (2006)
Firn, J., House, A. P. N. & Buckley, Y. M. Alternative states models provide an effective framework for invasive species control and restoration of native communities. J. Appl. Ecol. 47, 96–105 (2010)
Harvey, A. C. Forecasting, Structural Time Series Models and the Kalman Filter (Cambridge Univ. Press, 1989)
We thank S. Winderlich (Kakadu National Park) for facilitating data processing, and S. Cruickshank and G. Willis of the Northern Territory Department of Natural Resources, Environment, the Arts and Sport for providing gauging station data. M. Storrs, C. Murakami, F. Hunter, M. Hatt and F. Baird provided field assistance. A. Bourne assisted with data interpretation, and P. Milewski provided value insight into the mathematical analyses. S.S.S. received funding from the Australian Department of Agriculture, Fisheries and Forestry and A.R.I. received funding from a CSIRO McMaster’s Fellowship and United States National Science Foundation funds through the North Temperate Lakes Long Term Ecological Research Network and individual grants. S. R. Carpenter, Y. Buckley, and R. van Klinken provided comments on earlier versions of this manuscript.
The authors declare no competing financial interests.
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Schooler, S., Salau, B., Julien, M. et al. Alternative stable states explain unpredictable biological control of Salvinia molesta in Kakadu. Nature 470, 86–89 (2011). https://doi.org/10.1038/nature09735
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