The spread of species beyond their native habitat is a human-made environmental change on a global scale. Among vascular plants, over 16,000 species have now permanently settled in foreign countries. The majority of these "naturalizations" has taken place since the 1950s and predominantly in regions with considerable human influence.
Naturalized alien plants, also known as neophytes, can have major impacts on the affected regions' ecosystems. This is particularly evident in the case of invasive plants, which are spreading rapidly in new regions and outcompete the native flora. But what makes these plants so successful? Is it because they are exploiting an "ecological gap" in the foreign ecosystem, allowing them to thrive so easily? Or are they simply "naturally" good at expanding their range? In other words: Do plant species that are on the rise in their native habitats also become globally widespread as naturalized aliens?
Led by the University of Konstanz, an international research team found clear evidence supporting this theory. Their study compared the spread of 3,920 native plant species in ten European countries with how widely these species are naturalized globally. Europe is one of the world's "main exporters" of naturalized plants. "Our results show that many of the European plant species that successfully naturalize in foreign ecosystems are species that have expanded rapidly in their European home regions as well", explains Konstanz biologist Mark van Kleunen, who led the study. "Plants that are declining in their natural range, on the other hand, rarely succeed in settling in foreign areas".
The results of the study indicate that it could be the same characteristics that make plants successful both in their homelands and in foreign regions. The researchers identified common characteristics of these species: "In general, they are tall, ecologically versatile generalists that are highly competitive and prefer nutrient-rich habitats," summarizes Rashmi Paudel, first author of the study.
"If the plant species that are widespread and on the rise within their native habitats are essentially the same as those that spread successfully – and sometimes become invasive – in other regions of the world, then it stands to reason that both processes are at least based on similar biological mechanisms", concludes Paudel. "This could reflect that the selective pressures that have made certain species common in their native regions also have preadapted them for success as invaders. This could also reflect that such common species were more likely to be picked up, transported and introduced elsewhere." Observing the dynamics of the spread of native plants at home can thus provide valuable indications for assessing the likelihood of their establishment in new territories.
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