🌿 Plant collections, witnesses of genetic evolution over several centuries

According to a study from McGill University, plants collected centuries ago and preserved, flattened, in herbaria around the world could become valuable allies for monitoring genetic changes and extinction risks of plant species.

"In fact, by analyzing more than 51 million digitized herbarium sheets, the research team found that these collections could be used to reconstruct over 16,000 plant populations encompassing 41,000 species and spanning more than 250 years. This finding suggests that herbaria are valuable resources that allow scientists to monitor genetic diversity across a large part of the planet and gather information that has long been lacking: useful baseline data for conservation purposes.


"The countless plant specimens of humanity are a veritable goldmine of information about population genetic changes over time," explains Isaac Eckert, a doctoral student in the Department of Biology and lead author of the study. "Extracting and sequencing the genetic data contained in these collections would allow us to find and understand the causes of genetic changes much more easily."

As the research team points out, there is growing consensus on the importance of monitoring genetic changes for conservation purposes, because a loss of genetic diversity can reduce a species' ability to adapt and thereby increase the risk of extinction. Yet the population genetic data needed to track these changes remains scarce for most plant species, and this is even truer for long-term data.

To determine the usefulness of herbaria in this regard, the research team developed a method to group specimens into historical plant populations using information such as location, collection date, and life cycle traits of the species. The results show that it is possible to reconstruct hundreds of thousands of such populations using existing digitized collections. Sequencing them would allow researchers to estimate various genetic indicators for tens of thousands of species across 86% of the world's botanical regions.

"Surprisingly, our article shows that this is entirely possible," says the doctoral student, adding that these specimens "can be used to quantify genetic parameters for tens of thousands of species."

The study also highlights the potential benefits of digitizing other specimens. The authors estimate that digitizing all herbaria in the world would enable researchers to quantify the genetic diversity of more than half of all known plant species.

The results of this study show just how valuable herbaria are, notes the research team. In Canada alone, nearly 10 million plant specimens are preserved in more than 80 institutions: these are educational, cultural, and scientific resources. Yet many of these institutions today face budget constraints and staff shortages, and see the specter of closure looming.

"Herbaria often serve as absolutely essential bridges between science, policymakers, and the public," says Isaac Eckert. "A bit like a time capsule, they invite us on a journey through time, allowing us to go back decades or even hundreds of years to better understand how things have evolved and how to protect species, communities, and ecosystems for tomorrow."