Effects of the density of the invasive macrophyte Hydrilla verticillata and root competition on growth of one native macrophyte in different sediment fertilities
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The occurrence of non-native species at high densities may generate competition for resources and possibly exclude native species in various environments. We evaluated the effects of increased densities of the non-native invasive macrophyte Hydrilla verticillata on the growth of the native species Egeria najas in different sediment types and with only root interactions or root + shoot interactions. We tested the hypothesis that the effect of the invasive on the native species is density dependent and that it is greater when competition for light and nutrients occurs (root + shoot interactions). The results of these experiments demonstrated that increased density of the invasive species H. verticillata significantly decreased the growth of the native species independent of sediment type (sand or mud sediments). When plants competed for water and sediment resources (root + shoot interactions), the native species was more impacted by the invasive than when they competed only for water resources (only shoots interacting). Our results show that E. najas is probably unable to colonize sites highly colonized by hydrilla, and this applies to both sand and mud sediments. This outcome suggests that H. verticillata is a threat for E. najas and likely other native submerged species in South America.
KeywordsSubmerged macrophytes Exotic species Non-native species Invasions
We acknowledge with appreciation the comments provided by two reviewers and the handling editor, which improved the quality of our manuscript. We also acknowledge the “Parque Tecnológico da Itaipu” (PDTA/FPTI-BR) for providing a scholarship to MJ Silviera. SM Thomaz is especially thankful to the National Council for Scientific and Technological Development (CNPq) for providing continuous funding through a Research Productivity Grant. Finally, we thank Roberta Becker Rodrigues for helping in laboratory analyses. This research was partially funded by Itaipu Binacional.
- Barko JW, Adms MS, Clesceri NL (1986) Environmental-factors and their consideration in the management of submersed aquatic vegetation —a review. J Aquat Plant Manag 24:1–10Google Scholar
- Bremner JM (1965) Inorganic forms of nitrogen. In: Black CA (ed) Methods of soil analysis. American Society of Agronomy, MadisonGoogle Scholar
- Carmouze JP (1994) Metabolismo dos ecossistemas aquáticos: fundamentos teóricos, métodos de estudo e análises químicas. Ed: Edgard Blücher: FAPESPGoogle Scholar
- Madsen JD, Smith DH (1999) Vegetative spread of dioecious Hydrilla colonies in experimental ponds. J Aquat Plant Manag 37:25–29Google Scholar
- Madsen JD, Sutherland JW, Bloomfield JA, Eichler LW, Boylen CW (1991) The decline of native vegetation under dense eurasian watermilfoil canopies. J Aquat Plant Manag 29:94–99Google Scholar
- Pinheiro J, Bates D, DebRoy S, Sarkar D, R Core Team (2016) nlme: Linear and nonlinear mixed effects models. R package version 3.1-125. http://CRAN.R-project.org/package=nlme
- R Core Team (2016) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/
- Tassin J, Thiébaut G, Dutartre A (2011) Toward an objective perception of biological invasions. Rev Ecol Terre Vie 66:195–198Google Scholar
- Wang H, Wang Q, Bowler PA, Xiong W (2016) Invasive aquatic plants in China. Aquat Invasions 607:113–122Google Scholar