Native congeners provide biotic resistance to invasive Potentilla through soil biota

Abstract

Abstract. Soil biota can facilitate exotic plant invasions and these effects can be influenced by specific phylogenetic relationships among plant taxa. We measured the effects of sterilizing soils from different native plant monocultures on the growth of Potentilla recta, an exotic invasive forb in North America, and conducted plant-soil feedback experiments with P. recta, two native congeners, a close confamilial, and Festuca idahoensis, a native grass species. We also reanalyzed data comparing the ability of P. recta to invade experimentally constructed congeneric monocultures vs. monocultures of a broad suite of non-congeners. We found that monocultures as a group, other than those of the native P. arguta, were highly invasible by P. recta. In contrast, this was not the case for monocultures of P. arguta. In our first experiment, the biomass of P. recta was 50% greater when grown in soil from F. idahoensis monocultures compared to when it was grown in soils from P. arguta or P. recta monocultures. Sterilizing soil from F. idahoensis rhizospheres had no effect on the biomass of P. recta, but sterilizing soil from P. arguta and P. recta rhizospheres increased the biomass of P. recta by 108% and 90%, respectively. In a second experiment, soil trained by F. idahoensis resulted in a positive feedback for P. recta. In contrast, soils trained independently by each of the two native Potentilla species, or the closely related Dasiphora (formerly Potentilla) resulted in decreases in the total biomass of the invasive P. recta indicating strong negative feedbacks. Soil trained by P. recta also resulted in intraspecific negative feedbacks. Our results demonstrate substantial negative feedbacks for an invader in its nonnative range under certain conditions, and that native congeners can mount strong biotic resistance to an invader through the accumulation of deleterious soil biota.

Toward more robust plant‐soil feedback research

“…Even microbes occurring near a single plant would presumably be distributed to 20 conspecific glasshouse pots and ≥150 NAS mixture pots (Appendix S1: Fig. Other studies following similar methods suffer similar inconclusiveness (e.g., van der Putten et al 1993, Callaway et al 2013, Valliere and Allen 2016. Particular microbes could occur near a few plants just by chance, not because particular plant species caused the microbes to be present, so the Teste et al data do not confirm the first step of a PSF (Bever 1994).…”

Relatedness is a poor predictor of negative plant–soil feedbacks

“…Finally, it has been suggested that the effect of phylogeny may be dominant between close relatives, such that relatedness might predict plant–soil feedbacks between species interacting within taxonomic divisions such as genera or tribes within plant families (e.g. Burns & Strauss, 2011; Callaway et al ., 2013). However, we analysed plant–soil feedbacks from species interacting across a range of phylogenetic distances within two major plant families represented in our dataset (33 interactions within Asteraceae and 65 within Poaceae), and found the relationship between phylogenetic distance and plant–soil feedback interactions within these families was no different from that observed in the aggregate dataset (Poaceae: 0.0010; 95% CI: lower = −0.0079, upper = 0.0100, n  =   65; Asteraceae: 0.0058; 95% CI: lower = −0.0524, upper = 0.0640, n  =   27; Figs 2b-c).…”

“…Two widely proposed mechanisms by which negative plant–soil feedbacks operate are through accumulation of host-specific soil borne pathogens and nutrient resource depletion (Kulmatiski et al ., 2008; Mangan et al ., 2010; Burns & Strauss, 2011; Flory & Clay, 2013; Van der Putten et al ., 2013). Evidence that closely related plant species are more likely to share natural enemies or resources (Darwin, 1859; Webb et al ., 2006; Gilbert & Webb, 2007) has led to a belief that plants will perform less well on soils cultured by more closely related species (Brandt et al ., 2009; Burns & Strauss, 2011; Liu et al ., 2012; Callaway et al ., 2013; Sedio & Ostling, 2013) (Fig. 1).…”

Plant performance was greater in the soils of more distantly related plants for an herbaceous understory species

“…For example, Mehrabi and Tuck (2015) studied soil conditioning at the level of plant families, and found no correlation between phylogenetic distance and the strength of PSFs. Alternatively, Liu et al ’s (2012) comparison included congeners and confamilials, as have other studies finding that congeners similarly influence one another through the soil (Diez et al 2010; Burns and Strauss 2011; Callaway et al 2013). Because our study includes two confamilials, but no congeners, it is intermediate in phylogenetic scale, relative to other studies.…”