The species-specific effects of plant species on themselves and other plant species via their influence on soil microbial composition and abiotic soil properties are known as plant-soil feedbacks. Because feedbacks between plants and soil biota can differentially alter species performance and competitive ability (Bever, 2003), plant–soil feedbacks are thought to influence whether or not plant species can co-exist in multi-species communities, and the invasion success of exotic plant species (Bonanomi et al., 2005; Bell et al., 2006; van der Putten et al., 2007).
Positive plant-soil feedbacks (plant species experience enhanced performance from the soil microbial communities associated with conspecifics) are thought to increase coexistence while negative plant-soil feedbacks (plant species experience reduced performance from the soil microbial communities associated with conspecifics) are thought to promote invasion. However, a framework to predict which alien species will experience positive plant-soil feedbacks, and under what condition, is lacking.
In work published today in New Phytologist (Wandrag et al. 2020, colleagues and I* investigated whether phylogenetic relatedness could be used to predict the strength and direction of plant-soil feedbacks. We demonstrated that: 1) plant-soil feedbacks become increasingly unpredictable with increasing phylogenetic distance; 2) this unpredictability goes in both directions, with both more extreme positive and more extreme negative plant-soil feedbacks experienced by distance relatives; and 3) this pattern was driven by a few plant families that appear strongly responsive to soil microbial communities.
These results highlight an important role of co-evolution between some plant families and soil microbes, and further emphasize the need to examine the role of context dependence in driving the outcome pf PSF for plant species.
* Some of these ideas formed part of my successful Marie Curie Independent Fellowship research proposal (PSF-2-PREDICT; interrupted by COVID-19 but not forgotten!).