Shift in competitive ability mediated by soil biota in an invasive plant

Abstract

Understanding the shifts in competitive ability and its driving forces is key to predict the future of plant invasion. Changes in the competition environment and soil biota are two selective forces that impose remarkable influences on competitive ability. By far, evidence of the interactive effects of competition environment and soil biota on competitive ability of invasive species is rare. Here, we investigated their interactive effects using an invasive perennial vine, Mikania micrantha. The competitive performance of seven M. micrantha populations varying in their conspecific and heterospecific abundance were monitored in a greenhouse experiment, by manipulating soil biota (live and sterilized) and competition conditions (competition-free, intraspecific, and interspecific competition). Our results showed that with increasing conspecific abundance and decreasing heterospecific abundance, (1) M. micrantha increased intraspecific competition tolerance and intra-vs. interspecific competitive ability but decreased interspecific competition tolerance; (2) M. micrantha increased tolerance of the negative soil biota effect; and (3) interspecific competition tolerance of M. micrantha was increasingly suppressed by the presence of soil biota, but intraspecific competition tolerance was less affected. These results highlight the importance of the soil biota effect on the evolution of competitive ability during the invasion process. To better control M. micrantha invasion, our results imply that introduction of competition-tolerant native plants that align with conservation priorities may be effective where M. micrantha populations are long-established and inferior in inter-vs. intraspecific competitive ability, whereas eradication may be effective where populations are newly invaded and fast-growing.

Opposing effects of soil biota on a native plant shoot and root growth in the presence of a invasive competitor

“…However, soil effect on total or shoot mass did not signi cantly vary between the two species that grown in conspeci c and heterospeci c soils, contrary to a previous study (Wang et al 2021). The reason may be that southern and northern populations of each species responded differently to our experimental treatments (the impact of population as a random factor was signi cant), which is consistent with other studies (Allen et al 2018;Huang et al 2021). Moreover, soil effect on root mass was negative and neutral for the native and invasive plants that grown in heterospeci c soils under intraspeci c competition respectively, but their difference was insigni cant (Fig.…”

“…All soils were immediately stored in plastic bags and were kept at 4°C. Moreover, varying populations/genotypes of a speci c native or alien species can also interact differently with the same soil biota mainly due to the intraspeci c variation in plant population (Allen et al 2018;Huang et al 2021), so we collected stems for each species at GD and SD sites respectively (hereafter southern and northern populations). The collection of soils and plants was nished within two weeks In our lab, all soil samples of each site and rhizosphere species combination were mixed and passed through a 2.5-mm sieve to homogenize soil and remove plant tissue.…”

Stand biomass decreases towards the edge of a range expanding invasive plant, Mikania micrantha, but only on thick soil layers

“…Possibly, when grown in monoculture, core plants absorbed more soil resources and had a higher photosynthetic rate, or they generated less negative feedback with soil biota. A recent study found that populations of M. micrantha with higher conspecific cover had a higher tolerance of the negative soil biota effect (Huang et al 2021). Another possibility is that core plants may have reduced allocation to allelopathic substances (Lankau et al 2009), and thus they allocated more resources to growth.…”

Responses to nutrient addition, shading and clipping in a range expanding invasive plant, Mikania micrantha

“…Because stolons of M. micrantha often grow horizontally and intertwine with each other, it is hard to separate individual plants. Therefore, following previous studies (Huang et al, 2021(Huang et al, , 2022, we used average percent cover with five 2 m 2 quadrats as a surrogate for density. It must be admitted that percent cover of M. micrantha is dynamic, and because stolons ramify and elongate rapidly, the cover of range edge populations may be high, but at a larger scale plants of M. micrantha in edge populations may be infrequent and empty and suitable sites are plentiful for M. micrantha to occupy.…”

“…There are several possible reasons why plants of M. micrantha from different density and frequency populations grew similarly in each treatment. First, the spread distance and residence time of M. micrantha on Hainan island are short compared to those in other studies(Huang & Peng, 2016;Kilkenny & Galloway, 2013;Tabassum & Leishman, 2020), and plants cannot evolve to perform differently within such short spread distance and residence time.Second, disturbance and potential negative feedback with soil may cause M. micrantha density to change with time(Huang et al, 2021). Also, when M. micrantha density and frequency of occurrence are low, strong interspecific invaders such as Bidens pilosa and Sphagneticola trilobata may prevent M. micrantha from acquiring abundant resources.…”