Plant responses to diversity‐driven selection and associated rhizosphere microbial communities

Abstract

Plant diversity loss can alter plant–plant and plant–rhizosphere microbiome interactions. These altered interactions, in turn, may exert diversity‐driven selection pressure to which plants respond with phenotypic changes. Diverse plant communities may favour the survival and fitness of individuals with traits that avoid competition. Conversely, monocultures may accumulate species‐specific pests favouring greater investment in defence traits. Yet, it is unknown how altered plant rhizosphere interactions influence the plant diversity‐driven selection for altered plant phenotypes. We tested for plant diversity‐driven selection on plant above‐ground traits and how these traits are modified by their rhizosphere microbial communities after 11 years in experimental plant monocultures and mixtures. Plants propagated from monocultures or mixtures were grown in combination with their ‘home’ versus ‘away’ arbuscular mycorrhizal fungi (AMF) or non‐AMF microbes in two separate experiments using five and eight plant species, respectively. We hypothesized that plants in monocultures may be selected for better defence and better performance in association with rhizosphere microbial communities compared with plants in mixtures. Monoculture and mixture plants significantly differed in their above‐ground phenotypes. As predicted, plant traits related to defence (greater leaf mass per area and leaf dry matter content, reduced leaf damage) were more pronounced in monoculture plants in both experiments. Effects of the rhizosphere microbial communities, which generally enhanced plant growth, tended to be species‐specific. Significant three‐way interactions between diversity‐driven selection, AMF treatment and plant species showed that home versus away effects could be positive or negative, depending on plant species. We conclude that long‐term differences in plant diversity lead to selection for altered plant phenotypes. Such differences may be further modified in association with the AMF microbial communities derived from the different plant diversity treatments, but often outcomes are species‐specific. This suggests that plant species differ in their capacity to respond to diversity loss and associated changes in rhizosphere microbial communities, making it complicated to predict community‐level responses to such loss. A free Plain Language Summary can be found within the Supporting Information of this article.

How plant–soil feedbacks influence the next generation of plants

“…This is likely due to the generalist anti‐fungal qualities of the pyrrolizidine alkaloids produced by J. vulgaris (which have been found to stimulate J. vulgaris ‐specific pathogenic fungi) (Hol & Van Veen, 2002) and also higher concentrations of K in the soils conditioned by J. vulgaris . Taken collectively, our results suggest that intergenerational effects generated by PSFs could play a role in shaping grassland plant communities (Hahl et al, 2020; Zuppinger‐Dingley, Flynn, De Deyn, Petermann, & Schmid, 2016).…”

Effects of plant community history, soil legacy and plant diversity on soil microbial communities

“…In contrast to the strong effects of soil legacy on soil microbial communities, effects of plant community history were much weaker. This was unexpected because those same plant community history treatments led to significant plant evolutionary responses, including changes in plant–plant interactions (Zuppinger-Dingley et al, 2014; van Moorsel et al, 2018 and 2020) and even altered plant–soil feedbacks (Hahl et al, 2020; Zuppinger-Dingley et al, 2016). These evolutionary changes in the plant communities may have been too small to become influential on the diversity and composition of soil microbial communities that may need more time to develop or are too subtle to detect.…”

Co‐occurrence history increases ecosystem stability and resilience in experimental plant communities

“…In one of these experiments, the Jena Experiment in Germany (Weisser et al 2017), it was shown that divergent evolutionary changes of plant species in monocultures vs. mixtures during the first 8 yr contributed to this strengthening of the biodiversity–functioning relationship (Zuppinger‐Dingley et al 2014, van Moorsel et al 2018, 2019). Feedbacks between plants and soil organisms, however, had less explanatory power (van Moorsel et al 2018, Schmid et al 2019, Hahl et al 2020).…”