Prolific invasive plant will spread further as climate changes, warns a new global study

The EU Invasive Alien Species (IAS) Regulation aims to prevent and minimise the adverse impact of IAS. The European Commission’s first report on its implementation shows that Member States have taken effective measures. Nevertheless, the report also reveals that Member States have areas for improvement, including surveillance and control. 

To better gauge the level of threat and to inform risk management, decision-makers need to assess where IAS are likely to colonise, how easily they will spread and the factors that influence their colonisation and spread. 

This new study sheds light on the role of ‘climatic niches’ and evolutionary adaptation in the spread of species, and how these factors combine with the influence of human activities, such as trade. A climatic niche refers to the large-scale, climatic conditions that are necessary for a species to survive. It is described by levels of precipitation, temperature and altitude. 

Researchers can define the climatic niche for different species to help model the conditions that enable an invasive species to colonise and spread. 

The approach assumes that species are more likely to survive under conditions similar to their native range – a process known as niche conservatism. However, they can adapt to less favourable environments through natural selection or genetic changes – a process known as niche adaptation.

The researchers used a climatic niche model to predict the distribution of the globally invasive silverleaf nightshade (Solanum elaeagnifolium). They analysed whether the climatic niche had shifted during the plant’s global invasion and whether the spread was related to human drivers. 

Silverleaf nightshade is a herbaceous, woody perennial native to the Americas that is now widely distributed around the world. It thrives in a range of environmental conditions and across seasons. Its berries are toxic to livestock, and it hosts several pests, viruses, fungi and bacteria. It also competes with other crops for light, water and soil and affects the growth and biodiversity of native plants.

The model used occurrence data from research papers and online databases, such as the Global Biodiversity Information Facility. In total, 9 536 occurrence data were used in the modelling, including 7 860 from native ranges (North and South America) and 1 676 from invasive ranges (including Africa, Australia, China and Europe). 

The results showed that the global invasion of silverleaf nightshade was influenced substantially by both climatic changes and human activities, which included trade and transportation of goods. 

They also showed that some niche conservatism occurred because local conditions were conducive to growth of the species. 

However, the process of niche adaptation was more significant during invasion where silverleaf nightshade adapted to its environment through evolutionary processes. For example, silverleaf nightshade can now thrive in areas with a lower temperature and increased precipitation compared to its native range. This has happened in China and Europe. 

The opposite trend occurred in Africa and Australia where there was a niche shift towards higher temperature and decreased precipitation. The initial process during invasion was conservatism and this was followed by niche adaptation, as silverleaf nightshade had to move into more challenging areas. 

The study also showed that many highly suitable areas are yet to be invaded. This suggests that, if the climate changes, pro-active prevention and mitigation measures are needed to manage the spread of silverleaf nightshade. For example, the model found that silverleaf nightshade has already successfully adapted to local conditions in China and Africa whilst it has reached a stable population in Europe and Australia, which means it could potentially colonise these areas.

Source: 

Li, X., Chen, Y., Zhang, C., Wang, J., Song, X., Zhang, X., Zhu, Z. and Liu, G. (2024) Assessing the climatic niche changes and global invasion risk of Solanum elaeagnifolium in relation to human activities. Science of The Total Environment 954: 176723. 

To cite this article/service:

“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.