In order to understand the spread of the invasive North American plant known as ragweed, researchers looked at its genes.
Exotic species are one of the world’s biggest environmental issues. However, scientists are often unable to explain why and how this species spread so quickly.
Michael D. Martin, Professor of Evolutionary Genomics at Norwegian University of Science and Technology (NTNU) University Museum.
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) has identified the five most serious threats to species diversity worldwide. Land use change takes the lead, followed by direct resource exploitation, climate change, and pollution.
But the fifth concern probably many people haven’t thought of: alien species moving to places where they don’t belong. However, scientists know they are a huge problem.
However, it is uncertain how and why the exotic species spread so quickly. As a result, an international research group composed of some of the world’s best genetics experts has addressed the issue of common ragweed (Ambrosia Artemisifolia). Their findings were recently published in the journal science progress.
Why do weeds spread?
Native to the temperate regions of North America, ragweed was accidentally introduced to Europe in the 19th century through imported seeds and contaminated horse feed. In recent years, it has spread throughout a large part of the continent. Today, contaminated bird feed is a major source of input, so if you feed birds outside with imported seed, you should sort out the ragweed seed first.
Fortunately, many exotic species die before they can do any damage because they are unable to establish and adapt to a new environment. So what makes ragweed able to thrive? Their genes are key.
“We examined genetic material in 655 samples of common ragweed, of which 308 were from historical plant groups in the herb. Some were up to 190 years old and are from the time the plant was first introduced to Europe,” says Vanessa C. Baker, an expert in evolutionary genetics at NTNU University Museum.
In this way, the researchers were able to follow how the common ragweed had evolved since the plant’s arrival in Europe. This information provided answers that helped them better understand what led to the massive proliferation today.
But first, a little bit of information about why exotics is something we have to worry about.
causing problems all over the world
Exotic species cause problems in large parts of the world. In Norway, invasive threats include the salmon parasite Girodactylus SalarisMink, Sitka spruce, garden lupine, American lobster, pondweed Elodea canadensisred king crab, Canada goose, and giant hogweed.
The impact of man on nature is often at the heart of the problem. The sane man The population will exceed eight billion this year. Over the past 50,000 years, spreading species to parts of the world they don’t belong has been one of the ways humans have changed the planet.
These exotic species can outgrow those already in an area. Sometimes they simply eat the local species. Other times they eat their own food. They take over the habitats of species that are unable to counter the invaders’ ability to reproduce or make use of the resources in the area.
Common ragweed grows quickly and becomes large and thus can outcompete native species.
rabbits and cats
A famous example is the rabbits of Australia, where Europeans released a few rabbits on their newly discovered continent to make them more friendly and possessive of something to hunt. But in Australia, rabbits had no natural enemies that could keep the population under control.
Half a billion bunnies and massive destruction of nature later, bunnies aren’t so much fun anymore. Even after widespread disease outbreaks and intense population control efforts, Australia still has a few hundred million rabbits, not to mention over a million wild camels, 200 million frogs, and a few million foxes and wild cats.
Cats are one of the biggest threats to birds and other animals around the world. In the United States they kill up to four billion birds and more than 20 billion mammals annually, while in Norway outdoor cats kill about seven million birds. If you really want to help the environment, you should keep your cat indoors – and neuter her, too.
Tougher plants in Europe
So, back to Europe and the common ragweed. The research group found answers that could explain why this plant was so successful.
“Invasive populations in Europe prefer to develop genes that contribute to their defense, such as genes against pathogens that cause disease,” says Vanessa C. Baker.
In Europe, ragweed may have evolved in such a way as to make the plant more resistant to local threats.
Natural selection means that hardy plants have a significant advantage and multiply more often than less hardy specimens. This extended to the offspring who carried the advantage forward. Today, the tougher plants are completely taken over.
Other species contributed to the spread
The common ragweed also received help from outsiders along the way. The common ragweed reproduces sexually and makes up for the lack of partners on a new continent by coming out of its kind.
“We discovered that the plant crossed in Europe with closely related species that were introduced around the same time,” says Michael Martin.
This behavior meant that the common ragweed did not need the common ragweed plant nearby for the plant to gain a foothold where pollen from close relatives could be used to produce seeds. This is particularly useful in the early stages of introduction when population sizes are small.
Spread all the way to Denmark
The plant may also have escaped its North American enemies by coming here. In its normal range, it was susceptible to bacterial pathogens attacking it.
In Europe, native bacteria did not co-evolve with common ragweed, and therefore did not pose an immediate threat. An invasive plant can use more energy to grow and reproduce than to defend, which in turn gives it an advantage over native plants.
Common ragweed is also a problem in parts of its native North America. Agriculture and settlers helped spread the plant to parts of America where the plant is not native. You can read more on this topic here.
Denmark is currently the northern limit for common ragweed, and it is now more established there. The plant is currently not a threat in Norway, possibly due to the country’s harsh climate.
That’s fine for now – and also for those with pollen allergies who might fear the season lasts until November. We’ll see what happens if climate change hits warmer winters. Enduring cold winters and a little freezing every now and then isn’t a bad thing after all.
Reference: “Unraveling the genetic basis of an unusual plant invasion” by Vanessa C. Baker, Paul Batlay, Bent Petersen, Shane Sun, Jonathan Wilson, Gail C. Brilli, François Brittanyol, Christine Norkowski, Chris Lee, Fatima Sanchez Barrero, Gregory Owens, Jacqueline Wai Lee, Fabian L Kellner, Lotte van Bohemann, Shyam Gopalakrishnan, Miriam Goodall, Heinz Muller Scherer, Suzanne Lomen, Gerhard Carrier, Bruno Scheufele, Yan Sun, Bojan Kostantinovich, Love Dalinay, Peter Lauren Risberg, M. Thomas B Gilbert, Katherine A. Hodgins and Michael D. Martin, 24 Aug 2022, Available here. science progress.
DOI: 10.1126 / sciadv.abo5115
#plant #United #States #invaded #Europe