Priority effects and competition by a native species inhibit an invasive species and may assist restoration

Abstract

Selecting native species for restoration is often done without proper ecological background, particularly with regard to how native and invasive species interact. Here, we provide insights suggesting that such information may greatly enhance restoration success. The performance of the native vine, Pueraria lobata, and that of the invasive bitter vine, Mikania micrantha, were investigated in South China to test how priority effects (timing and rate of germination and seedling growth) and competition (phytochemical effects and competitive ability) impact invasive plant performance. We found that, in the absence of competition, the germination rate of M. micrantha, but not of P. lobata, was significantly affected by light availability. P. lobata seedlings also performed better than those of M. micrantha during early growth phases. Under competition, negative phytochemical effects of P. lobata on M. micrantha were strong and we found M. micrantha to have lower performance when grown with P. lobata compared to when grown by itself. Relative interaction indexes indicated that, under interspecific competition, P. lobata negatively affected (i.e., inhibited) M. micrantha, whereas M. micrantha positively affected (i.e., facilitated) P. lobata. Higher photosynthetic efficiency and soil nutrient utilization put P. lobata at a further advantage over M. micrantha. Field trails corroborated these experimental findings, showing little recruitment of M. micrantha in previously invaded and cleared field plots that were sown with P. lobata. Thus, P. lobata is a promising candidate for ecological restoration and for reducing impacts of M. micrantha in China. This research illustrates that careful species selection may improve restoration outcomes, a finding that may also apply to other invaded ecosystems and species.

Keywords: Mikania micrantha; Pueraria lobata; biotic interactions; competitive exclusion; ecological restoration; priority effect.

FIGURE 1

Changes in seedling growth of Mikania and Pueraria over time (average ± SD, n = 5). P – Pueraria seedlings; sP – Pueraria seedlings geminated from sulfuric acid‐treated seeds; M – Mikania seedlings. Red dotted lines indicate the equivalent level of the performance between Mikania and Pueraria seedling

FIGURE 2

Changes in phenotypic characteristics under interspecific competition (average ± SD, n = 15). 4M – four Mikania seedlings planted by itself; 3M1P – three Mikania seedlings planted with one Pueraria seedling; 2M2P – two Mikania seedlings planted with two Pueraria seedlings; 1M3P – one Mikania seedling planted with three Pueraria seedlings; 4P – four Pueraria seedlings planted by itself

FIGURE 3

Changes in Mikania biomass under interspecific competition (average ± SD, n = 5). 4M – four Mikania seedlings planted by itself; 3M1P – three Mikania seedlings planted with one Pueraria seedling; 2M2P – two Mikania seedlings planted with two Pueraria seedlings; 1M3P – one Mikania seedling planted with three Pueraria seedlings; 4P – four Pueraria seedlings planted by itself. Different letters above the error bars indicate significant difference at p < .05 (Duncan test)

FIGURE 4

Changes in Pueraria biomass under interspecific competition (average ± SD, n = 5). 4M – four Mikania seedlings planted by itself; 3M1P – three Mikania seedlings planted with one Pueraria seedling; 2M2P – two Mikania seedlings planted with two Pueraria seedlings; 1M3P – one Mikania seedling planted with three Pueraria seedlings; 4P – four Pueraria seedlings planted by itself. Different letters above the error bars indicate significant difference at p < .05 (Duncan test)

FIGURE 5

Comparison of relative interaction index (RII) between Pueraria and Mikania grown for 120 days. 3M1P – three Mikania seedlings planted with one Pueraria seedling; 2M2P – two Mikania seedlings planted with two Pueraria seedlings; 1M3P – one Mikania seedling planted with three Pueraria seedlings; 3P1M – three Pueraria seedlings planted with one Mikania seedling; 2P2M – two Pueraria seedlings planted with two Mikania seedlings; 1P3M – one Pueraria seedling planted with three Mikania seedlings

FIGURE 6

Changes in net photosynthetic rate (Pn) and water use efficiency (WUE) under interspecific competition (average ± SD, n = 9). 4M – four Mikania seedlings planted by itself; 3M1P – three Mikania seedlings planted with one Pueraria seedling; 2M2P – two Mikania seedlings planted with two Pueraria seedlings; 1M3P – one Mikania seedling planted with three Pueraria seedlings; 4P – four Pueraria seedlings planted by itself. Different letters above the error bars indicate significant difference at p < .05 (Duncan test)

FIGURE 7

Mikania regeneration and Pueraria performance after sowing Pueraria seeds in the field plots (average ± SD, n = 3). Lowercase letters above the black columns indicate significant difference in Mikania biomass, and capital letters above the gray columns indicate significant difference in Pueraria biomass at p < .05 (Duncan test)