Plant-soil feedbacks (PSFs) are important drivers of community diversity. While PSFs have been a fruitful framework for understanding interspecific community diversity, intraspecific variation has received little attention. Theory predicts that PSFs will be more negative as genetic similarity increases, which is predicted to lead to greater intraspecific diversity in the population. Intraspecific diversity is a diversity axis that a growing body of literature recognizes can have important implications for community dynamics. However, intraspecific PSFs have been rarely considered. Here, we investigate the effect of intraspecific diversity on PSF strength.
We measured interspecific and intraspecific PSFs following the standard PSF experimental approach. We used two geographically distant populations of two prairie species, Echinacea purpurea and Coreopsis lanceolata, to encompass both intra- and interspecific diversity. We trained soil microbial communities using pairs of plants that were either from the same population (low intraspecific diversity, low interspecific diversity), from different populations within the same species (high intraspecific diversity low interspecific diversity), or from different species (high interspecific diversity). We assessed the performance of plants grown in these differently trained soil microbial communities as biomass produced. We asked: What is the relative strength of intra- vs. interspecific PSFs?
Results/Conclusions
PSFs were more negative within species than among species (P < 0.05). Coreopsis and Echinacea both produced greater biomass when grown in microbial communities cultured by both species compared to microbial communities cultured only by their own species (P < 0.05 for both species). PSFs were also more negative within populations than among populations of a species (P < 0.01). Both Coreopsis populations produced greater biomass when grown in microbial communities cultured by two different Coreopsis populations compared to those cultured only by the same population (P < 0.05), but there was no difference for Echinacea (P = 0.23). PSFs were most negative when plants were grown in microbes trained by plants from their own population, and were least negative when were grown in soil microbes trained by both species. These results are consistent with the expectation that PSFs decrease with genetic similarity, and suggest that intraspecific genetic variation may be an important axis to consider when studying drivers of community diversity.