Clonal functional traits favor the invasive success of alien plants into native communities

Functional traits are frequently proposed to determine the invasiveness of
alien species. However, few empirical studies have directly manipulated
functional traits and tested their importance in the invasion success of
alien species into native plant communities, particularly under global
change. We manipulated clonal integration (a key clonal functional trait)
of four alien clonal plants by severing inter-ramet connections or keeping
them intact, and simulated their invasion into native plant communities
with two levels of species diversity, population density and nutrient
availability. High community diversity and density impeded the invasion
success of the alien clonal plants. Clonal integration of the alien plants
promoted their invasion success, particularly in the low-density
communities associated with low species diversity or nutrient addition,
which resulted in a negative correlation between performance of alien
plants and native communities, as expected under global change. Thus,
clonal integration can favor the invasion success of alien clonal plants
into degraded resident communities with a high degree of disturbance and
eutrophication. Our findings confirm the role of clonal functional traits
in facilitating alien plant invasions into native plant communities, and
suggest that clonal functional traits should be considered to efficiently
restore degraded communities heavily invaded by alien clonal plants.