Humans, and most animals we know, reproduce sexually—our offspring contain a genetic code that is a mix of both parents, allowing for greater genetic variability. This has been shown to confer adaptability to our ever-changing environment, because the diversity provided by the genetic mixing has the potential to generate favorable traits for future generations. Asexual species, on the other hand, do not have genetic variability like we do—each of their offspring has the exact same genetic makeup as their parent. How, then, do these species adapt to environmental changes? Surely, a toxin that affects one of them could potentially wipe out their entire population. New research from Wellesley College found out that one such asexual species, the weevil, has a surprising survival technique: they can pass down epigenetic changes to future generations.
Epigenetic changes are modifications to the DNA that tell the cell which part of the DNA to “read” in order to produce proteins, and which part to ignore. They do not change the actual DNA code, but they can dramatically change the amount and variety of proteins the cells make using the instructions of the DNA. Because epigenetic changes do not alter the actual DNA, it is often thought that they cannot be passed to offspring. However, this new study shows that these changes are indeed passed down through generations in the weevils.
The weevils are an asexual all-female species. Collecting the weevils from three different locations in the United States, the research team discovered that, despite being purchased from the same commercial source and having an identical genetic makeup, the weevils in different parts of the country produce different proteins and can digest different types of plants. This suggests that the weevils have somehow adapted to their environment without any changes to their DNA. When they looked into these weevils’ gene regulation, they found that the genes controlling plant detection, plant detoxification, and immune defense were very differentially “read” and expressed. In order to further test this, they fed lab weevils with different plants than they were used to. Similar epigenetic changes were seen as with the weevils that already eat those plants, and these adaptations were also passed onto the next generation.
This discovery has important implications for our understanding of asexual species and how they adapt to environmental changes. Specifically, many asexual species are pests or invaders, and learning how these species can adapt using epigenetic changes may help mitigate their negative impacts on plants or crops. Furthermore, this study also shows that genetic variation via sexual reproduction or mutation is not the only form of heritable variation a species can use to adapt to environmental changes, contrary to what we have always believed. Epigenetics, and other possible variations not encoded within our DNA, may be more important to our evolution than we think.
The first author of the study, Ava Mackay-Smith, is currently a Research Associate/Lab Manager in the Reilly lab at the Yale School of Medicine’s Department of Genetics.
Managing Correspondent: Wei Li
Press Article: The Fight To Adapt as an Asexual Invasive Species, Technology Networks.
Without Evolutionary Genetic Variation, Asexual Invasive Species Find New Methods of Adapting to Their Environment, SciTech Daily.
Original Article:Host-specific gene expression as a tool for introduction success in Naupactus parthenogenetic weevils, PLoS One.