Effects of pre-existing submersed vegetation and propagule pressure on the invasion success of Hydrilla verticillata
Article first published online: 9 OCT 2007
© 2007 The Authors. Journal compilation © 2008 British Ecological Society
Journal of Applied Ecology
Volume 45, Issue 2, pages 515–523, April 2008
How to Cite
Chadwell, T. B. and Engelhardt, K. A. M. (2008), Effects of pre-existing submersed vegetation and propagule pressure on the invasion success of Hydrilla verticillata. Journal of Applied Ecology, 45: 515–523. doi: 10.1111/j.1365-2664.2007.01384.x
- Issue published online: 9 OCT 2007
- Article first published online: 9 OCT 2007
- Received 29 January 2007; accepted 28 June 2007Handling Editor: Phil Hulme
- invasive species;
- priority effect;
- submersed macrophyte;
- Vallisneria americana
- 1With biological invasions causing widespread problems in ecosystems, methods to curb the colonization success of invasive species are needed. The effective management of invasive species will require an integrated approach that restores community structure and ecosystem processes while controlling propagule pressure of non-native species.
- 2We tested the hypotheses that restoring native vegetation and minimizing propagule pressure of invasive species slows the establishment of an invader. In field and greenhouse experiments, we evaluated (i) the effects of a native submersed aquatic plant species, Vallisneria americana, on the colonization success of a non-native species, Hydrilla verticillata; and (ii) the effects of H. verticillata propagule density on its colonization success.
- 3Results from the greenhouse experiment showed that V. americana decreased H. verticillata colonization through nutrient draw-down in the water column of closed mesocosms, although data from the field experiment, located in a tidal freshwater region of Chesapeake Bay that is open to nutrient fluxes, suggested that V. americana did not negatively impact H. verticillata colonization. However, H. verticillata colonization was greater in a treatment of plastic V. americana look-alikes, suggesting that the canopy of V. americana can physically capture H. verticillata fragments. Thus pre-emption effects may be less clear in the field experiment because of complex interactions between competitive and facilitative effects in combination with continuous nutrient inputs from tides and rivers that do not allow nutrient draw-down to levels experienced in the greenhouse.
- 4Greenhouse and field tests differed in the timing, duration and density of propagule inputs. However, irrespective of these differences, propagule pressure of the invader affected colonization success except in situations when the native species could draw-down nutrients in closed greenhouse mesocosms. In that case, no propagules were able to colonize.
- 5Synthesis and applications. We have shown that reducing propagule pressure through targeted management should be considered to slow the spread of invasive species. This, in combination with restoration of native species, may be the best defence against non-native species invasion. Thus a combined strategy of targeted control and promotion of native plant growth is likely to be the most sustainable and cost-effective form of invasive species management.