Photo: Kochia, southwest Montana. © 2020 Delena Norris-Tull
Evolutionary shifts: Their role in invasive plant success or failure
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020.
Uesugi and Kessler, 2013, conducted an experiment in an old field garden in New York, by planting tall goldenrod, Solidago altissima (native to North America and dominant in its native range; invasive in areas of Europe and Asia), in competition with Poa pratensis and with other Solidago altissima plants. They used insecticide on six of the 12 plots, to remove the natural herbivores that consume the goldenrod leaves.
Uesugi and Kessler, 2013, found that, after 15 years, the Solidago plants exhibited a greater increase in interspecific, than in intraspecific, competitive ability. In other words, an increased growth rate gave Solidago a greater competitive advantage against Poa pratensis than against other goldenrod plants. They also found that the Solidago had evolved increased production of polyacetylenes, which contain compounds that are allelopathic to Poa pratensis, but not against other Solidago plants. The results provided evidence that “release from herbivory alone can lead to an evolutionary increase in interspecific competitive ability,” and that the competition is “likely to be mediated by the increased production of allelopathic compounds.” Thus, the dominant [but in this case native] species promotes unstable coexistence, as it begins to dominate over other native species (refer to Chesson, 2000, in the section on Diversity for the conditions needed for stable coexistence).
While this study focused on a native species, Uesugi and Kessler’s study produced some support for BOTH the EICA hypotheses and the novel weapons hypothesis. Perhaps the reality is that plants that become dominant respond to their environment in a variety of manners, both as a result of the removal of natural predators, and by evolutionary pressures increasing both competitive ability and allelopathic compounds that repel predators. Uesugi and Kessler suspect that a similar evolutionary shift might occur in global locations where Solidago altissima is an introduced invader.
As does other research listed below, the research in this section provides examples of non-native plants evolving after they arrive in the introduced environment, and developing competitive advantages over native species over time. This points to the need for more research, not just on the various evolutionary pressures, but on the time factor. How long does it take for various species to evolve to the point of developing competitive advantages, and where in the sequence of stages in the Unified Framework of Blackburn, et al., 2011, does that evolution usually occur? Do different introduced species develop evolutionary advantages within different stages of the unified framework? Do a variety of barriers provide a variety of pressure points leading to evolutionary changes? And why do so many non-native species never become invasive in the introduced environment?
References:
Next Sections on research on the success of invasive species:
Evolutionary shifts: Their role in invasive plant success or failure
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020.
Uesugi and Kessler, 2013, conducted an experiment in an old field garden in New York, by planting tall goldenrod, Solidago altissima (native to North America and dominant in its native range; invasive in areas of Europe and Asia), in competition with Poa pratensis and with other Solidago altissima plants. They used insecticide on six of the 12 plots, to remove the natural herbivores that consume the goldenrod leaves.
Uesugi and Kessler, 2013, found that, after 15 years, the Solidago plants exhibited a greater increase in interspecific, than in intraspecific, competitive ability. In other words, an increased growth rate gave Solidago a greater competitive advantage against Poa pratensis than against other goldenrod plants. They also found that the Solidago had evolved increased production of polyacetylenes, which contain compounds that are allelopathic to Poa pratensis, but not against other Solidago plants. The results provided evidence that “release from herbivory alone can lead to an evolutionary increase in interspecific competitive ability,” and that the competition is “likely to be mediated by the increased production of allelopathic compounds.” Thus, the dominant [but in this case native] species promotes unstable coexistence, as it begins to dominate over other native species (refer to Chesson, 2000, in the section on Diversity for the conditions needed for stable coexistence).
While this study focused on a native species, Uesugi and Kessler’s study produced some support for BOTH the EICA hypotheses and the novel weapons hypothesis. Perhaps the reality is that plants that become dominant respond to their environment in a variety of manners, both as a result of the removal of natural predators, and by evolutionary pressures increasing both competitive ability and allelopathic compounds that repel predators. Uesugi and Kessler suspect that a similar evolutionary shift might occur in global locations where Solidago altissima is an introduced invader.
As does other research listed below, the research in this section provides examples of non-native plants evolving after they arrive in the introduced environment, and developing competitive advantages over native species over time. This points to the need for more research, not just on the various evolutionary pressures, but on the time factor. How long does it take for various species to evolve to the point of developing competitive advantages, and where in the sequence of stages in the Unified Framework of Blackburn, et al., 2011, does that evolution usually occur? Do different introduced species develop evolutionary advantages within different stages of the unified framework? Do a variety of barriers provide a variety of pressure points leading to evolutionary changes? And why do so many non-native species never become invasive in the introduced environment?
References:
- Blackburn, T.M., Pysek, P., Bacher, S., Carlton, J.T., Duncan, R.P., Jarosik, V., Wilson, J.R.U., & Richardson, D.M. (2011). A proposed unified framework for biological invasions. Trends in Ecology & Evolution, 26 (7), 333-339.
- Chesson, P. (2000). Mechanisms of maintenance of species diversity. Annual Review of Ecological Systems, 31, 343-366.
- Uesugi, A., & Kessler, A. (May, 2013). Herbivore exclusion drives the evolution of plant competitiveness via increased allelopathy. New Phytologist, 198 (3), 916-924.
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