Can we predict if a plant species will become exotic?

Newswise — Plant species become exotic when humans unintentionally or intentionally transport them to new regions outside their native range. In these new areas, these plants establish self-sustaining populations that rapidly reproduce and spread. This intricate process is influenced by various factors, such as the characteristics and genetics of the plants, making it challenging to establish universal guidelines for predicting or managing plant invasions. To address this, scientists from Spanish and Australian institutions have introduced a novel framework to identify predictors of invasiveness. Their study focuses on species that have either succeeded or failed to establish themselves in foreign regions despite following similar historical introduction routes.

Dr. Javier Galán Díaz from the University of Seville, Spain; Dr. Enrique G. de la Riva from the University of León, Spain; Dr. Irene Martín-Forés from The University of Adelaide, Australia; and Dr. Montserrat Vilà from Doñana Biological Station (EBD-CSIC), Spain, have presented their findings in a new paper published in the open-access journal NeoBiota.

In the past, little attention was given to the impact of translocating species to new regions, even though current policies now exercise strict control over the import and export of living organisms, including pests, between countries. This lack of consideration resulted in many species being transported to new regions without regard for their potential consequences," explains Dr. Javier Galán Díaz.

An illustrative example of this phenomenon is the extensive plant exchange that occurred among Mediterranean-type regions due to European colonialism. During this period, crops, cattle, tools, and materials were exported, potentially introducing the seeds of numerous plant species along the way.

Up until now, most research on plant invasions has sought to understand the success of exotic species by comparing their traits to those of native plant communities in the areas they invade or by comparing the traits of different plant species with varying levels of invasion within the same region. However, Dr. Galán Díaz points out that if we consider that the common plant species in European agricultural landscapes have likely been in contact with humans, they might have been inadvertently transported to other Mediterranean regions. Therefore, only those species that have actually succeeded in invading other regions possess unique characteristics that allowed them to establish and spread abroad.

Taking this perspective, the scientists discovered that when examining plant species transported from the Mediterranean Basin to other Mediterranean-climate regions like California, Central Chile, the Cape Region of South Africa, and Southwestern and South Australia, they found specific predictors of invasiveness. The species that became exotic were those with large distribution ranges, occupying diverse habitats in their native regions. Additionally, species with multiple dispersal vectors—such as seeds dispersed by animals, water, or wind—long bloom periods, and resource-efficient strategies for utilizing both above- and belowground resources, were more likely to become exotic. Crucially, most of this plant information is easily accessible from free and open-access repositories.

The researchers highlight the significance of understanding the factors that pre-adapt plant species to establish and thrive beyond their native ranges. This approach holds tremendous potential for management efforts. By using this framework, prediction models and management practices can be improved to mitigate the detrimental impacts of invasive species on local ecosystems.

Dr. Galán Díaz concludes by emphasizing the utility of existing information in identifying key species for monitoring purposes. Leveraging the wealth of data available, including observations from citizen science applications, strengthens screening systems, particularly in the era of Big Data. This collaborative approach enhances our ability to address and respond to the challenges posed by invasive plant species.