Photo: Wild Lettuce, southwest Montana. © 2020 Delena Norris-Tull
Second-genomes: Their role in biological invasions
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020.
“Both the initial absence and subsequent accumulation of symbiotic microbes, comprising myriad fungi, oomycetes, bacteria and viruses, can be a key determinant of invasiveness. The phenotype of an organism is not determined solely by the interaction of the genotype and the environment and its epigenome but also by the combined genomes of closely physiologically associated symbionts [‘second-genomes’]… Second-genomes comprised of closely associated symbionts can be a critical and semi-heritable (transmitted by the parents but also environmentally determined) determinant of plant adaptive traits” (Zenni, et al., 2017).
“When plant species are introduced to a new range, their second-genome may be accidentally or intentionally co-introduced…, leading to co-invasion… Alternatively, introduced plants can form ‘novel associations’ with native symbionts or co-xenic novel associations [meaning that both the plant species and the symbiont are non-native, and are not from the same region] can be formed between symbionts from different regions…. [which] can have serious fitness consequences…. The rates of association and the benefits from mycorrhizal associations may differ between native and invasive trees, providing a competitive advantage to invasive trees” (Zenni, et al., 2017).
“Pathogens can also co-invade, potentially hampering plant invasion success… {However], co-invading pathogens and native pathogens on invasive trees can transfer to native plants…, also contributing to tree invasions” (Zenni, et al., 2017).
“A lack of compatible mutualists may also be a factor in invasion failures… Some plant symbionts are capable of transmission directly from mother plant to seed, and hence spread along with the plant. However, most do not and must therefore spread independently from the plant host… Very little is known about second-genomes, particularly in the context of invasion” (Zenni, et al., 2017).
In relationship to epigenetics, Zenni, et al., 2017, proposed, “that co-evolved symbionts, both beneficial and harmful, which are closely physiologically associated with invasive species, contain critical genetic traits that affect the evolutionary dynamics of biological invasions.”
Zenni, et al., 2017, concluded that “integrating genetics with population dynamics is critical to better understanding the probability of either niche conservatism or niche evolution of an invader species in time. This is especially important since species niches are considered to be under constant natural selection pressures, and thus a lack of adaptive traits in the novel environment might not be as generalizable as previously thought.”
Reference:
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Second-genomes: Their role in biological invasions
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020.
“Both the initial absence and subsequent accumulation of symbiotic microbes, comprising myriad fungi, oomycetes, bacteria and viruses, can be a key determinant of invasiveness. The phenotype of an organism is not determined solely by the interaction of the genotype and the environment and its epigenome but also by the combined genomes of closely physiologically associated symbionts [‘second-genomes’]… Second-genomes comprised of closely associated symbionts can be a critical and semi-heritable (transmitted by the parents but also environmentally determined) determinant of plant adaptive traits” (Zenni, et al., 2017).
“When plant species are introduced to a new range, their second-genome may be accidentally or intentionally co-introduced…, leading to co-invasion… Alternatively, introduced plants can form ‘novel associations’ with native symbionts or co-xenic novel associations [meaning that both the plant species and the symbiont are non-native, and are not from the same region] can be formed between symbionts from different regions…. [which] can have serious fitness consequences…. The rates of association and the benefits from mycorrhizal associations may differ between native and invasive trees, providing a competitive advantage to invasive trees” (Zenni, et al., 2017).
“Pathogens can also co-invade, potentially hampering plant invasion success… {However], co-invading pathogens and native pathogens on invasive trees can transfer to native plants…, also contributing to tree invasions” (Zenni, et al., 2017).
“A lack of compatible mutualists may also be a factor in invasion failures… Some plant symbionts are capable of transmission directly from mother plant to seed, and hence spread along with the plant. However, most do not and must therefore spread independently from the plant host… Very little is known about second-genomes, particularly in the context of invasion” (Zenni, et al., 2017).
In relationship to epigenetics, Zenni, et al., 2017, proposed, “that co-evolved symbionts, both beneficial and harmful, which are closely physiologically associated with invasive species, contain critical genetic traits that affect the evolutionary dynamics of biological invasions.”
Zenni, et al., 2017, concluded that “integrating genetics with population dynamics is critical to better understanding the probability of either niche conservatism or niche evolution of an invader species in time. This is especially important since species niches are considered to be under constant natural selection pressures, and thus a lack of adaptive traits in the novel environment might not be as generalizable as previously thought.”
Reference:
- Zenni, R.D., Dickie, I.A., Wingfield, M.J., Hirsch, H., Crous, C.J., Meyerson, L.A., Burgess, T.I., Zimmermann, T.G., Klock, M.M., Siemann, E., Erfmeier, A., Aragon, R., Montti, L, & LeRoux, J.J. (Jan., 2017). Evolutionary dynamics of tree invasions: Complementing the unified framework for biological invasions. AoB Plants, 9 (1), 1-14 [plw085; 10.1093/aobpla/plw085].
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