Abstract
BackgroundFunctional group composition may affect invasion in two ways the effect of abundance, i.e. dominance of functional group; and the effect of traits, i.e. identity of functional groups. However, few studies have focused on the role of abundance of functional group on invasion resistance. Moreover, how resource availability influences the role of the dominant functional group in invasion resistance is even less understood.Methodology/Principal FindingsIn this experiment, we established experimental pots using four different functional groups (annual grass, perennial grass, deciduous shrub or arbor and evergreen shrub or arbor), and the dominant functional group was manipulated. These experimental pots were respectively constructed at different soil nitrogen levels (control and fertilized). After one year of growth, we added seeds of 20 different species (five species per functional group) to the experimental pots. Fertilization significantly increased the overall invasion success, while dominant functional group had little effect on overall invasion success. When invaders were grouped into functional groups, invaders generally had lower success in pots dominated by the same functional group in the control pots. However, individual invaders of the same functional group exhibited different invasion patterns. Fertilization generally increased success of invaders in pots dominated by the same than by another functional group. However, fertilization led to great differences for individual invaders.Conclusions/SignificanceThe results showed that the dominant functional group, independent of functional group identity, had a significant effect on the composition of invaders. We suggest that the limiting similarity hypothesis may be applicable at the functional group level, and limiting similarity may have a limited role for individual invaders as shown by the inconsistent effects of dominant functional group and fertilization.
Highlights
Determining the factors that control the invasion of exotic species is important in invasion biology [1,2]
We suggest that the limiting similarity hypothesis may be applicable at the functional group level, and limiting similarity may have a limited role for individual invaders as shown by the inconsistent effects of dominant functional group and fertilization
Invaders had more coverage and seedling numbers in pots dominated by annual grass (AG) and perennial grass (PG) than those dominated by D and E in 2011
Summary
Determining the factors that control the invasion of exotic species is important in invasion biology [1,2]. Evidence in support of limiting similarity is mainly from artificially established not natural communities [28] Abiotic factors, such as variations in nutrient availability, disturbance and propagule pressure, which were controlled in these artificially established communities, were postulated as the reason for the mixed results [28]. Found increased resource availability tended to reduce competition intensity between resident species and invaders Consistent with their result, many prior studies showed that high nutrient availability promoted community invasibility [29,30,31]. We postulate that competitive exclusion of invaders by functionally similar resident species may be affected by resource availability. We tested whether the effects of the dominant functional group on invaders changed with resource availability and what mechanisms led to such change
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