Photo: Pronghorn Antelopes in Sagebrush habitat, northern Wyoming. © 2017 Delena Norris-Tull
Competition-based coexistence mechanisms: Their role in maintaining plant diversity
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020.
Yuan and Chesson, 2015, used a mathematical model to examine the relative importance of temporal storage effect and relative nolinearity of competition in maintaining stable species coexistence. Finding that previous research tended to focus on the role of temporal storage effect in maintaining coexistence, they developed a model to examine the contributions of both types of competition-based coexistence mechanisms simultaneously. They stated that, “The mechanism relative nolinearity is named from the requirement that different species have different nonlinear responses to competition. If competition fluctuates over time, Jensen’s inequality means that the long-term growth rates, which are time averages of short-term growth rates, will be affected differently for different species. Relative nolinearity promotes coexistence when species drive fluctuations in competition in directions that favor their competitors. The coexistence mechanism thus involves both the relatively nonlinear growth rates and differences between species in their contributions to fluctuations in competition.”
Yuan and Chesson, 2015, discovered a variety of different ecosystems wherein both relative nolinearity and temporal storage effect contribute to species coexistence. They concluded that in some ecosystems storage effect is more important, in some ecosystems relative nolinearity is more important to stabilization, and in some ecosystems relative nolinearity can be destabilizing. The different effects of the two mechanisms seemed to be related to the amount of species variation in the length of life-span and the species’ variable sensitivities to environmental fluctuations. Thus, researchers need to consider both relative nolinearity and temporal storage effect when examining mechanisms of species coexistence.
As did Yuan and Chesson, 2015, Letten, et al., 2018, also found that researchers seemed to consider relative nonlinearity of competition much less important to species coexistence (or they ignored it all together) than the temporal storage effect. Letten, et al., 2018, conducted experiments on yeasts that indicated that both types of fluctuating effects work together and both are essential to stable coexistence.
References:
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Competition-based coexistence mechanisms: Their role in maintaining plant diversity
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020.
Yuan and Chesson, 2015, used a mathematical model to examine the relative importance of temporal storage effect and relative nolinearity of competition in maintaining stable species coexistence. Finding that previous research tended to focus on the role of temporal storage effect in maintaining coexistence, they developed a model to examine the contributions of both types of competition-based coexistence mechanisms simultaneously. They stated that, “The mechanism relative nolinearity is named from the requirement that different species have different nonlinear responses to competition. If competition fluctuates over time, Jensen’s inequality means that the long-term growth rates, which are time averages of short-term growth rates, will be affected differently for different species. Relative nolinearity promotes coexistence when species drive fluctuations in competition in directions that favor their competitors. The coexistence mechanism thus involves both the relatively nonlinear growth rates and differences between species in their contributions to fluctuations in competition.”
Yuan and Chesson, 2015, discovered a variety of different ecosystems wherein both relative nolinearity and temporal storage effect contribute to species coexistence. They concluded that in some ecosystems storage effect is more important, in some ecosystems relative nolinearity is more important to stabilization, and in some ecosystems relative nolinearity can be destabilizing. The different effects of the two mechanisms seemed to be related to the amount of species variation in the length of life-span and the species’ variable sensitivities to environmental fluctuations. Thus, researchers need to consider both relative nolinearity and temporal storage effect when examining mechanisms of species coexistence.
As did Yuan and Chesson, 2015, Letten, et al., 2018, also found that researchers seemed to consider relative nonlinearity of competition much less important to species coexistence (or they ignored it all together) than the temporal storage effect. Letten, et al., 2018, conducted experiments on yeasts that indicated that both types of fluctuating effects work together and both are essential to stable coexistence.
References:
- Letten, A.D., Dhami, M.K, Ke, P, & Fukami, T. (July 26, 2018). Species coexistence through simultaneous fluctuation-dependent mechanisms. Proceedings of the National Academy of Sciences of the United States of America (PNAS), 115 (26), 6745-6750.
- Yuan, C., & Chesson, P. (2015). The relative importance of relative nonlinearity and the storage effect in the lottery model. Theoretical Population Biology, 105, 39-52.
Next Sections on the role of diversity:
Next Sections on research on the success of invasive species: