I spent the end of last year writing my first book chapter with Jane Catford. Our chapter was on competition between native and alien plants. In it we provide an overview of some of the key concepts in competition theory and community ecology we think are relevant to understanding some important concepts in alien plant invasions, then discuss factors that influence competition between native and alien plant species.
Writing a book chapter was a fun experience: great to practice writing in a slightly less formal way than for journal articles, and to dig back into the literature on some topics that I spend a lot of time thinking about. I'm grateful to Anna Traveset and David Richardson for the opportunity to contribute.
A lot of the ideas we discuss in the chapter link to the grant Jane and Richard Duncan hired me under as a postdoc at the University of Canberra. Check out Wandrag et al. 2019 and O'Reilly-Nugent et al. 2020 for some of the other we work did.
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!).