Plant soil feedback strength in relation to large‐scale plant rarity and phylogenetic relatedness

Abstract

Understanding why some species are rare while others are common remains a central and fascinating question in ecology. Recently, interactions with soil organisms have been shown to affect local abundances of plant species within communities, however, it is not known whether they might also drive patterns of rarity at large scales. Further, little is known about the specificity of soil-feedback effects, and whether closely related plants share more soil pathogens than more distantly related plants. In a multi-species soil-feedback experiment (using 19 species) we tested whether regionally and locally rare species differed in their response to soil biota. Regional rarity was measured using range size or IUCN status and local rarity by typical abundance within an area. All species were grown on soils trained by a variety of regionally and locally rare and common species, which also varied in their degree of relatedness to the target. We found that, in general, regionally rare species suffered more than twice as much from soil biota than regionally common species. Soil cultured by regionally rare species also had a more negative effect on subsequent plant growth, suggesting they may have also accumulated more pathogens. Local rarity did not predict feedback strength. Further, soil trained by closely related plants had a more negative effect on growth than soil trained by distant relatives, which indicates a phylogenetic signal in the host range of soil biota. We conclude that soil biota may well contribute to plant rarity at large spatial scales, which offers a novel explanation for plant rarity and commonness. Moreover, our results show that phylogenetic relatedness between plants was a good predictor of the likelihood that two plant species interacted negatively via soil biota, which might mean that soil pathogens could prevent the coexistence of closely related plants and could drive patterns of phylogenetic overdispersion. Our results suggest that soil pathogens could restrict the ability of rare species to shift their ranges and might need to be considered by conservation biologists seeking to protect populations of rare plants.

When and where plant‐soil feedback may promote plant coexistence: a meta‐analysis

“…Distantly related plants had stronger negative PSF than closely related plants, consistent with closely related plants sharing pathogens (Gilbert & Webb ; Gilbert et al ; Parker et al ; Gilbert & Parker ). Our results are consistent with evidence that plants perform worse in soil cultured by closely related species than distantly related species (Liu et al ; Sweet & Burns ; Kempel et al ). Many plant communities are composed of species that are less related than expected by chance (Webb et al ; Cavender‐Bares et al ), and competition – decreasing as a function of phylogenetic distance – has been widely considered this pattern’s main driver (Cavender‐Bares et al , but see Mayfield & Levine ).…”

Plant geographic origin and phylogeny as potential drivers of community structure in root‐inhabiting fungi

“…The effect of plant–microbe interactions, a potential driver of plant community composition (Anacker et al, ; Bennett & Cahill, ; Kempel, Rindisbacher, Fischer, & Allan, ; Klironomos, ; Mangan et al, ; Teste et al, ), is determined by the net result of negative and positive effects by pathogens and mutualists (e.g. AM fungi), respectively (Reinhart & Callaway, ).…”

Winning and losing with microbes: how microbially mediated fitness differences influence plant diversity

“…; Kempel et al . , but see Maron et al . ), suggesting a link between the strength of these interactions and plant abundance.…”