Elevated nitrogen deposition and co-evolutionary history shape
competition between an invasive plant and its competitors during range
expansion
Abstract
During the range expansion of invasive plants, competitors shared
different co-evolutionary history with invasive plants, as well as
population differentiation, would have different effects on the response
of invaders to global change factors such as increased nitrogen
deposition. Disregard the community responses and potential adaptations
of invaders during the range expansion might bring misleading answers.
To address these challenges, we conducted a greenhouse experiment to
explore the synergistic effects between population differentiation
during range expansion and competitors on the invasion of
Galinsoga quadriradiata in response to increased nitrogen
deposition. Competitors (new or old that shared short or long
co-evolutionary history with the invader, respectively) were set to
compete with the invasive central and edge populations under different
nitrogen addition treatments. Galinsoga quadriradiata from the
central population (i.e., with longer residence time since invasion)
showed significantly higher total mass, reproduction, interspecific
competitiveness when compared to the individuals from the edge
population, and the magnitude of response to nitrogen addition
treatments was larger in the central population when planted in
isolation (single-culture). Nitrogen addition promoted growth and
reproductive performance of G. quadriradiata in single-culture,
in the presence of competitors this effect was weakened. The old
competitors acted more effectively than new competitors in inhibiting
the invader performance, mainly for the central population. Our results
indicate that population differentiation on growth and competitiveness
occurred during the range expansion of G. quadriradiata, with the
central population displaying higher invasiveness than the edge
population. The co-evolutionary history between invasive species and its
competitors has been suggested to be probably not in favor of invasive
plants, especially for central populations. Our results highlight the
synergistic and non-additive role of population differentiation and
shared co-evolution history between invasive species and its competitors
in the range expansion of invaders in the context of global change
factors.