American Journal of Botany最新文献

Plants are the homes and hosts of a vast diversity of microbiota. These microbes help plants access nutrients, mimic plant hormones to alter plant traits, synthesize new compounds that help plants defend against enemies, and so much more. Their pervasiveness and power means that they also likely alter many of the phenomena long studied by plant ecologists and evolutionary biologists from plant coexistence to speciation. Ignoring microbes means that we may be under- or overestimating the magnitude of or misidentifying the proximal causes of several common outcomes in plant ecology and evolution. Yet, accounting for these cryptic copilots also is not easy because not only the presence of microbes, but also their community composition and evolutionary histories determine their effects. Here we describe the outsized roles microbial communities may play in three fundamental areas of plant ecology and evolution: maternal effects, phenotypic plasticity, and natural selection. These three topic areas are not exhaustive, and microorganisms likely influence many more study areas in plant biology (e.g., plant coexistence [Bever et al., 1997], the expression of genetic variation [O'Brien et al., 2019], and perhaps even reproductive isolation and speciation as observed in insect systems [Tiffin et al., 2001]). However, our goal is to demonstrate some of the potential consequences of ignoring these microscopic millions and to convince plant ecologists and evolutionary biologists that considering microbial effects in our experiments may improve our understanding of how things actually work in a natural world that is dominated not by plants and plant genes but by the microbes associating with them.

Maternal effects in plants have been recognized for over a century (Roach and Wulff, 1987), and plants have been relying on maternally inherited microbial symbionts for plant defense, abiotic stress tolerance, and even the very basics of plant function (e.g., plant capture of microbial ancestors of chloroplasts) since their earliest origins (Sagan, 1967). Yet, we are only now beginning to investigate the roles that diverse soil and foliar microbial communities play in promoting adaptive maternal environmental effects.

Maternal environmental effects result when the maternal environment influences offspring phenotype. Moms often do this by altering resource provisioning to offspring (e.g., seed mass) or altering the chemical composition or epigenetic profile of seeds (e.g., transmission of mRNA or proteins or DNA methylation). Because soil and foliar microbes affect plant growth and can mimic and alter plant signaling pathways, they may also affect maternal resource availability and/or alter chemical signals to offspring (Figure 1a). In this way, microbial communities may function much like any other environmental factor. However, microbial communities may be even more likely to cause matern

Soil microorganisms play a critical role in shaping the biodiversity dynamics of plant communities. These microbial effects can arise through direct mediation of plant fitness by pathogens and mutualists, and over the past two decades, numerous studies have shined a spotlight on the role of dynamic feedbacks between plants and soil microorganisms as key determinants of plant species coexistence. Such feedbacks occur when plants modify the composition of the soil community, which in turn affects plant performance. Stimulated by a theoretical model developed in the 1990s, a bulk of the empirical evidence for microbial controls over plant coexistence comes from experiments that quantify plant growth in soil communities that were previously conditioned by conspecific or heterospecific plants. These studies have revealed that soil microbes can generate strong negative to positive frequency-dependent dynamics among plants. Even as soil microbes have become recognized as a key player in determining plant coexistence outcomes, the past few years have seen a renewed interest in expanding the conceptual foundations of this field. New results include re-interpretations of key metrics from classic two-species models, extensions of plant–soil feedback theory to multispecies communities, and frameworks to integrate plant–soil feedbacks with processes like intra- and interspecific competition. Here, I review the implications of theoretical developments for interpreting existing empirical results and highlight proposed analyses and designs for future experiments that can enable a more complete understanding of microbial regulation of plant community dynamics.