Ecosystems

New Modelling Reveals Opportunities to Blunt Plant Invasions Before They Reach a Tipping Point

An examination of herbarium records has helped track the dynamics of plant invasions.
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A new study of herbarium records by Ming Ni (倪明) shows that the spread of invasive plant species is not at a steady rate. The findings, published in Plants People Planet, will help ecologists plan strategies for combatting plant invasions more efffectively.

Ni used herbarium collections and literature reports to track how quickly invasive plants spread in their new habitats. After plotting the data, he tried different models to see what gave the best mathematical fit. This way Ni could uncover if invasive species spread at a constant rate, or in fits and starts.

Art produced by Midjourney from the prompt Kudzu invading grasslands in the style of Roy Lichtenstein. Broad sweeps of yellow and green dominate the image, possibly indicating hills or clouds. At the bottom something that might be kudzu sits over rather yellow looking grass or hair.
‘Kudzu invading grasslands in the style of Roy Lichtenstein’. Image: Midjourney.

“The two models incorporating three phases, that is, segmented linear model and sigmoid model, provided better fits than did the three remaining models only incorporating one or two phases. Both segmented linear and sigmoid models suggest slow spreading at the beginning of invasions (lag phase), followed by rapid spreading after a threshold was attained (accelerating phase) and, finally, reaching maximum extent without expanding any further (stable phase),” writes Ni.

The three-phase models highlight the importance of controlling plant invasions while they are at an early stage, and so spreading slowly. Ni argues that preventing plant invasions from reaching the accelerating phase will more effectively reduce the environmental damage from the invaders.

Five graphs of scattered points with lines passing through them. The models are Simple linear model, Quadratic model, Michaelis-Menten model, Sigmoid model and Segmented linear model.
Five models fitting the relationship between minimum residence time and invasion ranges across all species. Source: Ni 2022.

Ni found that the early lag phase, where plants spread slowly as they gain a foothold in a new location, was similar to many studies, but longer than some recent studies. Ni suggests that not everyone has included early literature reports in their research, leading to an underestimate of the length of this lag phase.

Ni comments on the importance of reliable records. He writes, “This research also highlights the importance of natural history collections (here, herbarium records) in helping us to understand invasion dynamics. Digging more deeply into these historical records can extend our knowledge in terms of understanding invasion dynamics as well as our ability in invasion management.”

READ THE ARTICLE

Ni, M. 2022. ‘Herbarium records reveal multiple phases in the relationship between minimum residence time and invasion ranges of alien plant species’, Plants People Planet. https://doi.org/10.1002/ppp3.10327

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