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Goal: Sustain Our Nation’s Forests and Grasslands On the move: Patterns of plant invasions

Global patterns of biodiversity, such as north-south patterns of species richness, have long been an important topic in ecology and evolutionary biology. While most studies focus on native species, little effort has been devoted to global patterns of plant invasions. In a recent study, Forest Service scientists found substantial north-south variations in plant invasions on a global scale—with important implications for management and conservation.

Kudzu covering a landscape
Like many other invasive plant species in the southeastern United States, Kudzu (Pueraria montana) is an example of a poleward (in this case, northward) spreading invasive species. USDA Forest Service photo.

Southern Research Station scientists and colleagues studied nonnative plant invasions across the globe and found striking patterns. Although the number of invasive species generally declined as the latitude increased, the highest numbers of nonnative species occurred at the same latitude in both hemispheres, around 40 degrees. On continents, researchers observed a humped pattern of increase-then-decline across latitudes.

Overall, islands showed significantly higher invasion levels in continental regions. The same pattern of decreasing invasion levels towards higher latitudes was also found on islands. Islands showed more variability in invasion levels at low latitudes, nearer the equator. In continental regions, only the mid-latitudes had high variability with both low and high invasion levels.

In addition to latitude, people are a dominant factor explaining the observed patterns in plant invasion levels. Species pool size, climate warming, and biotic resistance are also likely to play a role.

The scientists identified latitudes with invasion hotspots where management is urgently needed, as well as areas where preventing future invasions is critical. These include latitudes with many areas of low invasions but high conservation potential. Future work is needed to closely monitor species invasions across latitudes and major geographic regions, with a focus on links from local to regional and global scales.

Principal Investigators
Qinfeng Guo, Research Ecologist
4854 - Eastern Forest Environmental Threat Assessment Center
Strategic Program Area
Invasive Species
Latitudinal patterns of alien plant invasions
External Partners
U.S. Geological Survey
Czech Academy of Sciences
Durham University, United Kingdom
University Vienna, Austria
University of Goettingen, Germany
University of Konstanz, Germany
German Centre for Integrative Biodiversity Research (iDiv)
Charles University, Czech Republic