Summary 1.While an appreciation of plant-soil feedbacks (PSF) continues to expand for community and ecosystem ecology, the eco-evolutionary mechanisms and consequences of such feedbacks remain largely unknown or untested. 2. Determining the cause and effect of plant phenotypes is central for understanding these ecoevolutionary dynamics since phenotypes respond to soil selective gradients that are, in turn, modified by plant traits. Genetic variation in plant phenotypes can change soil processes and biotic communities; oppositely, soil gradients and microbial communities can influence the expression and evolution of plant phenotypes. 3. Although these processes represent the two halves of genetic based PSF, research in these areas has developed independently from one another. Greater connectivity between research on ecosystem consequences of plant genetic variation and soil selective gradients that drive plant phenotypic evolution will create novel and important opportunities to link ecology and evolution in natural systems. 4. Papers in this special feature build on the inherent ecological and evolutionary processes involved in PSF, outlining many ways to identify and test mechanisms that connect ecosystem ecology and evolution.

Past research on plant-soil feedbacks (PSF), largely undertaken in highly controlled greenhouse conditions, has established that plant species differentially alter abiotic and biotic soil conditions that in turn affect growth of other conspecific and heterospecific individuals in that soil. Yet, whether feedbacks under controlled greenhouse conditions reflect feedbacks in natural environments where plants are exposed to a range of abiotic and biotic pressures is still unresolved. To address how environmental context affects PSF, we conducted a meta-analysis of previously published studies that examined plant growth responses to multiple forms of competition, stress, and disturbance across various PSF methodology. We asked the following questions: (1) Can competition, stress, and disturbance alter the direction and/or strength of PSF? (2) Do particular types of competition, stress, or disturbance affect the direction and/or strength of PSF more than others? and (3) Do methods of conducting PSF research (i.e., greenhouse vs. field experiments and whether the source of soil inoculum conditioning is from the field vs. greenhouse) affect plant growth responses to PSF or competition, stress, and disturbance, or their interactions? We discovered four patterns that may be predictive of what future PSF studies conducted under more realistic conditions might reveal. First, relatively little is known about how PSF responds to environmental stress and disturbance compared to plant-plant competition. Second, specific types of competition enhanced negative effects of soil microbes on plant growth, and specific environmental stressors enhanced positive effects of soil microbes on plant growth. Third, whether PSF experiments are conducted in the field or greenhouse can change plant growth responses. And, fourth, how the soil conditioning phase is conducted can change plant growth responses. With more detail than previously shown, these results confirm that environmental context writ large can change plant growth responses in PSF Beals et al. PSF Differs With Competition, Stress experiments. These data should aid theory and predictions for conservation and restoration applications by showing the relative importance of competition, stress, and disturbance in PSF studies over time. Lastly, these data demonstrate how variation in experimental methods can alter interpretation and conclusions of PSF studies.

We examined the hypothesis that climate‐driven evolution of plant traits will influence associated soil microbiomes and ecosystem function across the landscape. Using a foundation tree species, Populus angustifolia, observational and common garden approaches, and a base population genetic collection that spans 17 river systems in the western United States, from AZ to MT, we show that (a) as mean annual temperature (MAT) increases, genetic and phenotypic variation for bud break phenology decline; (b) soil microbiomes, soil nitrogen (N), and soil carbon (C) vary in response to MAT and conditioning by trees; and (c) with losses of genetic variation due to warming, population‐level regulation of community and ecosystem functions strengthen. These results demonstrate a relationship between the potential evolutionary response of populations and subsequent shifts in ecosystem function along a large temperature gradient.

Summary 1.Predicting the response of communities and ecosystems to range shifts as a consequence of global climate change is a critical challenge confronting modern evolutionary ecologists. 2. Indirect genetic effects (IGEs) occur when the expression of genes in a conspecific neighbouring species affects the phenotype of a focal species, and the same concept applies for interspecific indirect genetic effects (IIGEs) except that the neighbouring species is then required to be heterospecific. 3. Theory and empirical data indicate that indirect genetic effects and interspecific indirect genetic effects have fundamental roles in understanding the consequences of genotypic diversity, evolutionary feedbacks, the co-evolutionary process and coadaptation and are a primary mechanism for the broad ecological and evolutionary dynamics that are likely to be a consequence of climate change. 4. When indirect genetic effects and interspecific indirect genetic effects occur along environmental gradients, both positive and negative feedbacks can evolve, resulting in regions of strong local adaptation and competition as well as regions of complementarity and facilitation. Such evolutionary dynamics have direct consequences for how individuals interact and evolve in mixture and drive the services ecosystems provide. 5. Integrating indirect genetic effects and interspecific indirect genetic effects, feedbacks and diversity effects along environmental gradients represents a major conceptual, theoretical and empirical frontier that must be considered to understand the whole-system consequences of climate change on biodiversity and the services ecosystems provide.