Does relatedness of natives used for soil conditioning influence plant-soil feedback of exotics?

Abstract

The naturalisation hypothesis has been gaining attention recently as a possible mechanism to explain variations in invasion success. It predicts that exotic genera with native representatives should be less successful because of an overlap in resource use and of the existence of common specialised enemies.In this study, we tested whether native congenerics have more negative impact on exotic species than heterogenerics by increasing the effects of soil pathogens. We sampled soil in populations of three exotic species (Epilobium ciliatum, Impatiens parviflora and Stenactis annua) at sites with and without respective congeneric species. This soil was used as an inoculum for cultivating the first plant cohort, which included exotics, as well as native congenerics and heterogenerics. The conditioned soil was subsequently used for cultivating the second cohort of plants (exotics only). We found no consistent impact of relatedness of conditioning species on exotic growth. Although soil conditioned by congeneric E. hirsutum had the largest reduction on the performance of E. ciliatum, the final biomass of S. annua was lowest when grown in soil conditioned by itself. There was no effect of stimulating species on the biomass of I. parviflora. In both experimental phases, performance of exotics was improved when cultivated with sterilised inoculua, indicating the dominance of soil generalist pathogens. However, the biomass of S. annua was increased most by congeneric-stimulated inoculum from congeneric sites, suggesting a possible role for specialised symbionts. Our results suggest that variations in invasion success of at least some exotics may be affected by speciesspecific interactions mediated by the soil biota.

Soil fungi of three native tree species inhibit biomass production and shift biomass allocation of invasive Mikania micrantha Kunth

“…Similarly, biomass production of the alien species Impatiens parviflora following cultivation in conspecific soil was consistent with biomass production in native species soil [11]. However, the invasive species Stenactis annua was found inhibited by soil microbes characteristic of its two sympatric native species, Erigeron acer and Geum urbanum [11]. Data from the current and previous studies, therefore, indicate differences in how certain invasive species respond to the presence of soil microbes.…”

“…These data suggested the absence of a species-specific pathogen that specifically inhibited MM biomass production in the three native tree soils. Similarly, biomass production of the alien species Impatiens parviflora following cultivation in conspecific soil was consistent with biomass production in native species soil [11]. However, the invasive species Stenactis annua was found inhibited by soil microbes characteristic of its two sympatric native species, Erigeron acer and Geum urbanum [11].…”

“…Soil microbes have frequently been identified as integral in native species successful resistance against invasion; native species Erigeron acer and Geum urbanum reduced biomass production in the invasive Stenactis annua via the interaction with soil microbial flora [11]. Among soil microbial organisms, fungi have been shown to play a key role in resisting invasive plants.…”

Native congeners provide biotic resistance to invasive Potentilla through soil biota

“…For example, Ska´lova´and Pyšek (2009) found that a suite of Impatiens species easily recruited into plots dominated by native Impatiens species; however, plots dominated by the invasive I. glandulifera resisted encroachment by all other congeners. Dosta´l and Palečkova´(2010) found that soil conditioned by the native Epilobium hirsutum reduced the performance of the invasive E. ciliatum more than that of other genera, but found no consistent effect of soil conditioning by two different congeneric pairs of natives and exotics. Agrawal et al (2005) compared pathogen attack on 15 pairs of native and exotic (not all were invasive) congeners and found that native congeners experienced far more negative soil feedbacks than exotic congeners, indicating that even closely related exotic taxa might escape consumer regulation.…”

Independent variations of plant and soil mixtures reveal soil feedback effects on plant community overyielding

“…In this feedback phase, plants were harvested 6 weeks after planting, which is a short duration, but not uncommon in plant–soil feedback studies (Bonanomi, Giannino & Mazzoleni ; Dostál & Palečková ; van de Voorde, van der Putten & Martijn Bezemer ). The rationale for this short duration, however, was the need for disentangling the individual plants below‐ground.…”