Invasive Plants Can Hide in Plain Sight for up to 320 Years Before Expanding Rapidly

Invasive plants are widely recognized as one of the major threats to biodiversity and ecosystem functioning worldwide.

However, a new study reveals that these plants can also pose a hidden danger that is often overlooked by researchers and managers: they can stay dormant for decades or even centuries before rapidly expanding and causing ecological damage.

Dormancy: A Deceptive Strategy

The study, published in Nature Ecology and Evolution, was led by researchers from the University of California, Davis, who analyzed data from over 5,700 species of invasive plants across nine global regions.

They found that these plants, once introduced into new environments, have the uncanny ability to remain undetected for extended periods before suddenly springing to life and spreading.

This phenomenon, known as dormancy, is a strategy that allows plants to survive unfavorable conditions, such as drought, cold, or herbivory, by reducing their metabolic activity and entering a state of suspended animation.

Dormant plants can persist in the soil as seeds or vegetative structures, such as bulbs, tubers, or rhizomes, waiting for the right trigger to germinate or sprout.

Dormancy is not unique to invasive plants, but it is especially advantageous for them, as it enables them to evade detection and eradication efforts, as well as to adapt to novel environments and exploit opportunities for invasion.

According to the study, dormancy can range from a few months to several centuries, depending on the species and the environmental factors.

Some examples of invasive plants that exhibit long dormancy periods are:

Sycamore maples

(Acer pseudoplatanus), which were introduced to the United Kingdom in the 17th century as ornamental trees, but remained dormant for 320 years before expanding and displacing native oak and ash trees.

Ribwort plantain

(Plantago lanceolata), which was introduced to the United States in 1822 as a medicinal herb, but stayed dormant for 177 years before spreading and becoming a noxious weed to livestock and native plants.

Velvetleaf

(Abutilon theophrasti), which was introduced to the United States in the 18th century as a possible fiber crop, but lay dormant for 50 years before expanding and threatening corn, soybean and other crops as it sucks up water and nutrients.

Implications for Management and Conservation

The discovery of dormancy in invasive plants has profound implications for the management and conservation of ecosystems worldwide. It means that invasive plants are not only an immediate threat, but also a long-term challenge that requires innovative solutions.

The study's lead author, Mohsen Mesgaran, an assistant professor in the Department of Plant Sciences at UC Davis, highlighted the need for revised strategies in dealing with invasive plants.

He said that the traditional focus on immediate threats must expand to include long-term monitoring and management practices aimed at identifying and mitigating risks posed by dormant invasive plants.

He also suggested that more research is needed to understand the mechanisms and triggers of dormancy in invasive plants, as well as to develop methods to detect and eliminate them before they become a serious problem. He said that this could involve using molecular tools, remote sensing, or citizen science.

Mesgaran concluded that dormancy is a deceptive and dangerous trait that amplifies the threat level of invasive plants. He warned that ecosystems worldwide are sitting on a ticking time bomb, and that we need to act fast and smart to defuse it.