Phylogenetic conservatism of plant-soil feedback contributes to plant relative abundance in the field

Background/Question/Methods

Plant interactions with macro-mutualists (e.g., seed dispersers, pollinators) and antagonists (e.g., herbivores and pathogens) often exhibit phylogenetic conservatism, but conservatism of interactions with soil microorganisms is understudied. We assembled one of the best available datasets to examine conservatism in plant-soil feedback, which includes a diversity of native and exotic plant species from a natural community, allows simultaneous examination of soil feedbacks from both whole soil communities and soil mycorrhizae, and links plant-soil feedback with plant occurrence data from the field. We measured plant-soil biota interactions for co-occurring native and exotic plant species using three common log response ratio metrics: (1) biomass of plants grown in soils with a history of conspecifics vs. a history of heterospecifics, “soil feedback”; (2) biomass of plants with and without inoculation with a common arbuscular mycorrhizal fungi species, “Glomus feedback”’; and (3) biomass of plants inoculated with AM fungi cultured by conspecifics vs. no inoculation, “AM fungi community feedback”. 

Results/Conclusions

We found phylogenetic conservatism in soil feedback and AM fungi community feedback, indicating plant relatives typically shared their responses to soil microbes. Moreover, conservatism was stronger among natives than exotics. Incorporating phylogenetic non-independence, we recovered a strong relationship between plant field abundance and soil feedback (adj. r² = 0.62). Our best model included all three soil feedback metrics, suggesting complementarity in the ways in which whole soils, a dominant AM fungi, and AM fungal communities contribute to plant performance in the field. The results combine to indicate that shared plant response to soil biota may influence the abundance and distribution of close plant relatives in nature.