Evolutionary processes affect all living organisms, and their impact also affects agricultural practices. Understanding evolutionary outcomes and harnessing such processes may be particularly beneficial to improving existing practices and developing new strategies in a rapidly changing world.
Agricultural Evolution. Image Credit: Scharfsinn/Shutterstock.com
Evolutionary processes integrated within agriculture
Evolution can be defined as the process of gradual changes in heritable characteristics over time. These characteristics involve genetic and phenotypic changes in the traits of species. Accordingly, evolutionary changes involve physiological, morphological, and other fitness-related traits. Such changes in crop or livestock species directly affect agricultural practices as the productivity, resilience, and sustainability of species can be modified through trait changes.
Many processes are integrated within evolution, including mechanisms of natural selection, genetic drift, gene mutation, assortative mating, and stochastic effects, which contribute to the evolutionary history of all living species including agricultural value.
For instance, a review published in May 2020 discussed the origin, evolutionary, and agricultural importance of amphicarpy, which describes how certain plants produce seeds both above and below ground. Amphicarpy occurs in 13 genera of flowering plants and is associated with a high degree of plasticity in seed characteristics as well as reproduction and has evolved as a means for plants to reproduce in variable and stressful environmental conditions.
Importantly, the review presented how the strategic use of growing amphicarpic legumes in regions experiencing unstable food production, such as the tropics, may be economically valuable. Amphicarpic species can provide high yield supplies as well as improve pastures, prevent soil erosion and improve soil fertility to bolster additional crop production. Harnessing traits such as amphicarpy could therefore contribute towards greater food security.
Evolutionary mechanisms are integrated within agriculture practices to maximize productivity. However, anthropogenic modifications in farmed species also alter evolutionary processes as practices such as crop manipulation, artificial selection during breeding, and growth supplements can change life-history traits, population dynamics, and the genetic makeup of species.
Evolution in practice within agriculture
The concept of evolutionary history plays a key role as it shapes the viability of species considered in agriculture. Specifically, the origin, geographic range, and genetic diversity of species can affect the long-term sustainability and yield of crops and livestock.
This was demonstrated in a study from 2018 in the journal Genome Biology and Evolution by a team of international researchers. Using the genomic datasets of 7 different domesticated species, researchers found a significantly reduced genetic variation and an increased proportion of nonsynonymous amino acid changes in every domestic species considered aside from one.
This deterioration was hypothesized to be attributed to population bottlenecks resulting in changes in the genetic makeup of species. This accumulation of deleterious variants can lead to a reduction in the individual fitness of the crops considered. The evolutionary implications of gene dynamics are therefore key to identify and predict potentially harmful changes on a species level, which is of significance as contemporary agriculture relies on a limited number of crop types.
The effect of agricultural practices on evolution
The characteristics of evolutionary mechanisms themselves can be changed in agriculture. For instance, processes of artificial selection across species may be accelerated as cross-hybridization of crops as well as the breeding of livestock will generate speciation barriers in otherwise distantly related species.
However, the nature of changes imposed by agriculture remains contested. A key example is how domestication and farming of species may increase the speed of evolutionary changes (i.e., evolutionary rates). This was believed to occur across domesticated species as humans selectively breed individuals based on phenotypic variants, ultimately changing the morphology, physiology, or genomic composition, of a species much faster than in the wild.
Contrary to popular belief, this concept of increasing evolutionary rates under domestication was disproven in a 2018 study comparing evolutionary rates between natural and domesticated breeds of dogs and pigs, revealing that populations had similar rates of changes in skull shape despite the interference of artificial selection in domesticated populations.
Agriculture can also disrupt evolutionary processes with unpredictable impacts. This was demonstrated in recent work studying the disruption of plant–microbial symbiosis due to evolutionary trade-offs, genetic costs, and relaxed selection in domesticated crops. Published in May 2020, American researchers reviewed existing literature on the extent to which domestication can modify symbiotic relationships and developed predictive evolutionary models to determine the significance of various hypotheses.
From the model and the collection of existing studies, the plant traits regulating the symbiosis were found to be disrupted firstly due to the alteration of the trait by artificial selection, secondly due to the accumulation of deleterious mutations generated by breeding, and thirdly due to the neutral selection of the trait of interest in agricultural conditions. Such effects have wide-ranging repercussions for crops, which often are characterized by a variety of symbiotic associations.
Harnessing evolutionary mechanisms for agricultural purposes
Evolutionary processes play key roles in shaping agricultural practices. Understanding such processes also provides key insight into improving existing practices as well as developing new ones.
A recent example examining elements of regional gene flow and genetic drift of cattle breeds revealed varying phylogenetic relationships between 6 populations of cattle, identifying areas of migration edges and source populations. Such information characterizing the longevity, genetic composition, and history of cattle can then be used to inform policies and bolster the effectiveness of farming practices.
Harnessing evolutionary mechanisms through molecular techniques has proved particularly beneficial and of increasing interest. Specifically, the popularity and success of gene editing techniques have pushed evolutionary dynamics to the forefront of food and agricultural science, with recent developments in the inheritance of CRISPR-based changes demonstrating the significance of evolutionary mechanisms in progressing agricultural science.
- Geiger, M., & Sánchez-Villagra, M. R. (2018). Similar rates of morphological evolution in domesticated and wild pigs and dogs. Frontiers in Zoology, 15(1), 1. doi:10.1186/s12983-018-0265-x
- Lehocká, K. (2020). Assessment of genetic drift and migration in six cattle breeds. Acta Fytotechnica et Zootechnica, 23(Monothematic Issue), 46–51. doi:10.15414/afz.2020.23.mi-fpap.46-51
- Li, Q., & Yan, J. (2020). Sustainable agriculture in the era of omics: knowledge-driven crop breeding. Genome Biology, 21(1), 1. doi:10.1186/s13059-020-02073-5
- Makino, T., Rubin, C.-J., Carneiro, M., Axelsson, E., Andersson, L., & Webster, M. T. (2018). Elevated Proportions of Deleterious Genetic Variation in Domestic Animals and Plants. Genome Biology and Evolution, 10(1), 276–290. doi:10.1093/gbe/evy004
- Porter, S. S., & Sachs, J. L. (2020). Agriculture and the Disruption of Plant–Microbial Symbiosis. Trends in Ecology & Evolution, 35(5), 426–439. doi:10.1016/j.tree.2020.01.006
- Zhang, K., Baskin, J. M., Baskin, C. C., Cheplick, G. P., Yang, X., & Huang, Z. (2020). Amphicarpic plants: definition, ecology, geographic distribution, systematics, life history, evolution and use in agriculture. Biological Reviews, 95(5), 1442–1466. doi:10.1111/brv.12623