Kings Study Unveils Spatial Scales Role in Plant Invasions

Researchers from King's College London have uncovered why decades of ecological studies have produced conflicting evidence about species invasions.

Their findings, published in Ecology, show that the spatial scale of analysis fundamentally alters conclusions about how introduced plants interact with native communities.

The study, led by Dr Maria Perez-Navarro in the Department of Geography, tested two long-standing hypotheses - preadaptation and limiting similarity - using 33 years of data from Cedar Creek Ecosystem Science Reserve in Minnesota.

These hypotheses, rooted in Darwin's theory of natural selection, offer opposing predictions: invaders succeed either because they resemble native species (preadaptation) or because they differ enough to avoid competition (limiting similarity).

By analysing plant communities at two fine scales - 0.5 m² neighbourhood plots and 40 m² site transects - the team demonstrated that both hypotheses can be correct, but at different scales.

At the neighbourhood level, differences in physical features such as height and leaf structure drove success, supporting limiting similarity. At the site level, environmental filtering favoured species with traits similar to the community, consistent with preadaptation.

"The scale you choose changes the story," said Dr Perez-Navarro. "Processes like competition operate at very fine scales, while environmental filtering becomes more important as you zoom out."

The research also revealed that evolutionary closeness and physical plant traits often tell different stories. Introduced species closely related to natives were more abundant at both scales, even when trait-based analyses suggested otherwise.

"This shows why we need to look at both evolutionary relationships and functional traits," added Dr Jane Catford, co-author and Professor of Ecology at King's. "They capture different dimensions of how communities assemble."

The findings have practical implications for biodiversity management. "If we want to predict which species will become invasive, we need to consider scale and multiple measures of similarity," said Dr Perez-Navarro.

The work underscores King's commitment to advancing global understanding of biodiversity and invasive species management.

It was supported by the European Research Council and conducted in collaboration with the University of Graz and the Australian National University.