Led by the accomplished Marianthi Karageorgi, her Institute for New Economic Thinking team of researchers have had an extraordinary first year. Now they’re figuring out the genetic dominance dynamics. A new research study behind a recent article in Nature Ecology & Evolution on September 15 provides the first empirical support for the theory of “dominance reversal.” Such a mechanism would facilitate populations’ long-term ability to adapt to and cope with changing environments. This discovery pushes against the long-held concept of dominant versus recessive gene interactions found in evolutionary biology.
Their inquiry was guided both by experimental evolution methods and an outdoor orchard used specifically for T. podocarpi evolution to unfold. Their goal was to get at the idea of dominance reversal. In doing so, they spectator large populations of fruit flies evolving under nearly-natural conditions. The study took place in an outdoor pen with one fruit-bearing peach tree. Researchers tracked the populations from early summer until late fall.
To explore the effects of environmental pressures, the researchers employed two sets of cages: one exposed to a pesticide pulse and another left untreated. They took a representative sample of the flies from each cage at two generations intervals. This generated unprecedented power to monitor pesticide resistance and the genome-wide frequencies of gene variants in real time. Their findings showed that dominance reversal was highly important to this evolutionary response of the populations.
Insights from the Study
These results showed that the combined use of imidacloprid and methomyl shifted allele frequencies at the resistance locus. It additionally affected loci across the whole chromosome. Karageorgi noted, “When we applied pesticides, we didn’t just change [allele] frequencies at the resistance locus—we affected loci all across the chromosome, which danced to the pesticide pulse, increasing and then decreasing in frequency.”
These observations were the first time dominance reversal was documented in response to sudden environmental changes. This discovery backfills the hypothesis that this mechanism has surely been in action out in nature for millions and millions of years. Petrov commented on the broader implications of their findings, stating, “The effects of this reversal are global and very short-lived.” This indicates how quickly populations are potentially able to adapt to sudden changes, like the application of a new class of pesticides.
It was those observations which sparked the interest of these researchers, who sought to provide a mathematical framework to support their findings. Dominance reversal was present in their study. What this modeling showed us was that genetic interactions with varying environmental effects tend to be very dynamic. It implies that organisms somehow possess a hidden, magical talent to change in high speed.
Implications for Environmental Adaptation
The consequences of this research go far beyond drosophila. Understanding the idea of dominance reversal could help us make better predictions about how species will react with changing environment around them. Karageorgi emphasized that “this mechanism could have been operating in nature for millions of years—helping insects maintain resistance to chemical defenses that vary seasonally with host plant availability.” In the midst of this crucial moment, this understanding is sorely needed. Agricultural practices have therefore turned increasingly towards synthetically developed insecticides which usually duplicate natural plant chemical defenses.
Petrov added further context by comparing the phenomenon to an earthquake: “It’s a little bit like an earthquake—as if buildings fell in Chicago and we feel the shaking here, and then suddenly in both places it’s calm again.” This analogy goes a great distance to show the ephemeral but forceful genetic responses environmental stressors can suddenly pack.
Moreover, Petrov pointed out the potential for rapid adaptation: “Let’s say you haven’t used pesticides for 20 years. The moment you add pesticides again, they’ll rapidly respond and resist them.” This phenomenal adaptability to a changing world further highlights the need to account for population genetic diversity as our populations confront relentless changes in our environment.
Future Directions
The research team’s work paves the way for these and other efforts to study in real-time how genetic mechanisms drive evolution. Understanding these dynamics will not only enhance scientific knowledge but may inform future agricultural practices and pest management strategies.
As Petrov stated, “This field is trying to understand what forces are involved in evolution, how you measure them, and how much of an effect they have. Often these forces are hidden from us.” The intricate dynamics of these interactions requires continued exploration into evolutionary mechanisms. This is all the more critical as ecosystems face unprecedented, rapid changes from anthropogenic forces.