Non-native species can remain dormant for decades or even centuries before spreading. Invasive plants can remain dormant for decades or even centuries after being introduced into the environment before spreading rapidly and wreaking ecological havoc, according to new research conducted by the University of California, Davis.

A study published in the journal Nature Ecology and Evolutionstudied more than 5,700 invasive plant species in nine regions around the world. This represents the most comprehensive analysis of plant invasions conducted to date, said senior author Mohsen Mesgaran, an associate professor of plant science at UC Davis.

“The longer it is inactive, the more likely we are to ignore it,” Mesgaran said. “This delay allows them to remain undetected and contributes to their emergence as a serious invasive threat. They are like invasive time bombs.”

Long rest periods

The international team found that almost a third of the invasive plants they analyzed showed an average lag time of 40 years between introduction and rapid spread. The longest dormant period of a plane tree in Great Britain was 320 years.

Consider an ordinary lawn grass Plantago lanceolataAccording to the report, plantain, also known as mountain ash or buckthorn, has the longest dormancy period in the United States. The plant, which harms livestock and native plants, was introduced to the United States in 1822 and is widely used there. Touted as a possible fiber crop, velvet leaf can remain dormant for 50 years before growing larger, threatening corn, soybeans and other crops as it absorbs water and nutrients.

Non-native species are generally introduced in two ways: accidentally or through deliberate importation for medicinal, ornamental, agricultural and other purposes. Approximately 65% ​​of invasive plants in California were intentionally introduced.

“This lag phase may have played a role,” Mesgaran said. “They didn’t know. With the development of trade, transportation and tourism, we will have more problems.”

global herbarium

Researchers compiled a list of invasive plants from Australia, Great Britain, Ireland, Japan, New Zealand, Madagascar, South Africa, Japan and the United States and obtained global data on where and when using herbarium records that were digitized and accessible online. when species are observed.

They then looked at trends to determine whether the species exhibited dormant stages and, if so, for how long. A time series analysis was applied to identify lag periods, followed by a second analysis comparing the climate in the recession phase and the expansion phase.

Some species that invaded different areas had different dormancy periods depending on location. Mesgaran said that in 90 percent of cases, climatic conditions differed during the distribution of the species, indicating that plants were waiting for suitable conditions or adapted to survive in a once unsuitable environment.

Future Planning

Knowing that problems may arise in the future is key to controlling pests and preventing widespread infestation and economic losses in the future. This means manufacturers, politicians and others need to take rest periods into account.

“The problem is that most of the risk assessment models we have to see whether species are going to be invasive and whether there will be a pest problem in the future, they don’t take into account that lag phase or dormancy phase,” Mesgaran said. said. “That doesn’t mean they won’t be a problem, it’s just the calm before the storm.”

The next step of the research will be to examine the local climate of the invasive species relative to conditions in these new locations.