Assembly of nonnative floras along elevational gradients explained by directional ecological filtering

Area of Science:

• Ecology
• Invasive Species Biology
• Biogeography

Background:

• Nonnative species richness typically decreases along environmental gradients like elevation.
• This pattern is often attributed to invaders lacking adaptations for extreme conditions.

Purpose of the Study:

• To investigate the traits of nonnative plants at high elevations.
• To understand the mechanisms driving nonnative species richness gradients.

Main Methods:

• Analyzed nonnative plant species at high elevations globally.
• Compared traits of nonnative species with native species.
• Examined the role of introduction pathways and climatic tolerance.

Main Results:

• Nonnative plants at high elevations exhibit broad climatic tolerances, unlike specialized native species.
• Species with narrow elevational ranges drop out, a process termed directional ecological filtering.
• Climatic generalists are more successful in colonizing extreme high-elevation environments.

Conclusions:

• Invasion resistance is influenced by introduction pathways, not solely by extreme site conditions.
• Directional ecological filtering explains nonnative species richness gradients and native flora assembly.
• Future introductions of specialized nonnative species may increase invasion risk in mountain ecosystems.