We are—depending on who you ask—either on the brink of or in the thralls of Earth’s sixth mass species extinction. What is not in doubt is that just one species deserves most of the blame: Homo sapiens—aka us.
Human activity is warming our climate and many species are failing to adapt; experts predict that as a result, by the end of the century as many as one in six species will be in danger of extinction.
Mammals are going extinct at rates faster than ever, as are other vertebrates. While invertebrates like coral are being hit even harder. Overall, rates of species extinction are accelerating to the point where they may soon rival those during the mass extinction event that killed almost all of the dinosaurs (Birds, which are descendants of dinosaurs, are one of the few remaining species from the Mesozoic era).
Many in the scientific community are studying the effects of climate change on organisms in an attempt to see what, if anything, can be done to stave off this extinction crisis. One avenue that has produced interesting results: what we’ve learned from studying epigenetic changes in different species that may be due to the changing climate.
In January 2016, researchers at the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany reported that they had observed epigenetic changes in guinea pigs in response to changing temperatures. The sample size was small, just five wild male guinea pigs, but it was the first time epigenetic changes, methylation in this case, were observed in mammals in response to artificially raised temperatures. Changes in the amount of methylation, which is the addition of a small molecule to DNA which reduces or shuts off the activity of a gene, was found on at least 10 genes known to be involved with temperature regulation in the animals.
The researchers don’t believe these observed epigenetic changes were permanent to the guinea pigs or any species for that matter. Nor do they think that epigenetic changes alone will save the species from extinction. The fact that they found no transmission of these changes to the next generation supports the idea that epigenetics is not rewriting evolutionary theory. But they do theorize that if some species can respond to changing climates via epigenetic modifications on temperature regulation genes, it may allow them to stall extinction long enough to allow for the much slower process of evolution to occur.
The loss of our coral reefs has been the focus of a great deal of conservation efforts; coral, made up of thousands of tiny animals called polyps, are quite possibly the most vulnerable organisms on the planet to climate change. Reefs support a tremendous amount of life and biodiversity and are of tremendous economic value; unfortunately some models predict that left unchecked, climate change could wipe out the coral, which build the valuable reefs, by the end of this century. This has led scientists to focus on both the genetics and epigenetics of the tiny intervebrates in an “all hands on deck” approach to saving them.
Coral have surprised researchers by exhibiting more heat-tolerance than initially anticipated, and they do so in a variety of unexpected ways, including recruiting heat tolerant algae.
“The corals from warmer locations have babies with higher heat tolerance,” said Line Bay from the Australian Institute of Marine Science in Townsville, Queensland. Bay’s work has also uncovered that mother’s appear to pass on genes for heat resilience more efficiently than fathers. This has led to the identification of a number of genes that are involved in heat tolerance; many unexpectedly are mitochondrial genes.
An individual coral’s temperature sensitivity (i.e. the range of temperatures it can survive in) appears to be determined almost entirely by genetics. But some like, researchers Yi Jin Liew and Manuel Aranda from the King Abdullah University of Science and Technology in Saudi Arabia, believe that this sensitivity can be “stretched” beyond their genes through making epigenetic changes to those genes involved with temperature sensitivity. In a lab setting, coral exposed to an environmental stressor (eg. excessive heat) early in life better tolerate it later in life through changes in methylation on genes associated with heat tolerance. They explained how this knowledge could be used in a conservation strategy:
The ability to generate pre-adapted coral colonies and larvae via epigenetic conditioning will allow the creation of seeding populations that repopulate the reefs naturally, without the potential reduction of genetic diversity caused by artificially selecting corals, or the monumental effort required to restore the reef through continuous transplantation of single colonies.
There has been considerable research exploring epigenetic effects in plants. In particular several labs are attempting to direct epigenetic changes on significant genes to engineer crops that could withstand climate change or other extreme weather effects like droughts.
In Norway, scientists studying spruce trees have found evidence that epigenetic modifications on certain genes may play a role in how these trees respond to drastic changes in temperature. During, winter, spruce trees become incredibly hardy and are able to withstand temperatures of up to 200° C below zero. But during the spring, the spruce have almost no tolerance for the cold. Scientists have observed that changes in epigenetic factors on certain genes in the spruce between the seasons may play a roll in the temperature window that these plants can withstand. Similar to coral, plants exposed to more stress early in life better tolerate environmental stress over time—a process that could involve epigenetic modifications on specific genes that vary in their activity from season to season.
A 2013 study published in Nature found evidence to support the idea that epigenetic modifications on heat tolerance genes may allow a common mustard seed, Arabidopsis thaliana, time to evolve tolerance—similar to what the guinea pig researchers hypothesized.
Will understanding epigenetics save any species?
Epigenetics is a very controversial field, and there is still a lot to be learned. One thing that is highly debated is how transient epigenetic factors are—meaning what Liew and Aranda propose for engineering temperature resilient coral may be a fruitless if the coral simply lose the marks once they are seeded back into the wild. John Greally of the Albert Einstein College of Medicine also cautions that variations in epigenetic changes seen between individuals of the same species may actually be explained by individual genetic variation or that epigenetic modifications may be artifacts of other events and not consequential to overall physiology.
This puts in doubt how valuable studying these changes in organisms will have on saving them and other endangered ones. Even with the possibility we could control or artificially drive epigenetic changes (the goal of a lot of cancer drug research), it’s still more likely that other factors matter more in gene behavior like transcription factors, interactions with other genes, and regulatory sequences.
But that doesn’t mean what we are learning about epigenetics can’t play a role in conservation efforts. Monitoring changes may prove an invaluable way to identify which species are coping best with rising temperatures and which ones need extra attention. Studying gene behavior and epigenetics may also play significant roles in researching what genes are important for adaption to temperature changes. Knowing what genes are most important for this could help determine conservation efforts such as selective breeding programs or even genetic engineering to push evolution in the right direction. In these ways studying epigenetics could play a vital role in species conservation—it just probably won’t be the savior of any species.
Nicholas Staropoli is the associate director of GLP and director of the Epigenetics Literacy Project. He has an M.A. in biology from DePaul University and a B.S. in biomedical sciences from Marist College. Follow him on twitter @NickfrmBoston.