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In nature, plant species simultaneously interact with many different mutualistic partners. These mutualists may influence one another through direct interference or indirectly by competing for shared reward resources or through alteration of plant traits. Together, these mutualists also may combine to affect plant hosts in ways that may not be predictable based on pairwise interactions. Given that the outcome of mutualistic interactions often depends on environmental conditions, multi‐mutualist effects on one another, and their plant hosts may be affected by global changes. Here, we grew focal plants under simulated global warming conditions and manipulated the presence of partner mutualists to test how warming affects the outcome of interactions between focal plants and their partners (nitrogen‐fixing rhizobia, ant defenders, and pollinators) and interactions among these partner mutualists. We find that warming alters the fitness benefits plants receive from rhizobium resource mutualists but not ant mutualists and that warming altered plant investment in all mutualists. We also find that mutualist partners interact, often by altering the availability of plant‐produced rewards that facilitate interactions with other partners. Our work illustrates that global changes may affect some but not all mutualisms, often asymmetrically (e.g., affecting investment in the mutualist partner but not plant host benefits) and also highlights the ubiquity of interactions between the multiple mutualists associating with a shared host.

 

Microorganisms can help plants and animals contend with abiotic stressors, but why they provide such benefits remains unclear. Here we investigated byproduct benefits, which occur when traits that increase the fitness of one species provide incidental benefits to another species with no direct cost to the provider. In a greenhouse experiment, microbial traits predicted plant responses to soil moisture such that bacteria with self‐beneficial traits in drought increased plant early growth, size at reproduction, and chlorophyll concentration under drought, while bacteria with self‐beneficial traits in well‐watered environments increased these same plant traits in well‐watered soils. Thus, microbial traits that promote microbial success in different moisture environments also promote plant success in these same environments. Our results demonstrate that byproduct benefits, a concept developed to explain the evolution of cooperation in pairwise mutualisms, can also extend to interactions between plants and nonsymbiotic soil microbes.

 

Adaptation drives the diversity of form and function observed in nature and is key to population persistence. Yet, adaptation can be limited by a lack of genetic variation, trade-offs, small population size, and constraints imposed by coevolving interacting species. These limits may be particularly important to the colonizing populations in restored ecosystems, such as native prairies restored through seed sowing. Here, we discuss how constraints to adaptation are likely to play out in restored prairie ecosystems and how management decisions, such as seed mix composition, prescribed fire, and strategic site selection, might be used to overcome some of these constraints. Although data are still limited, recent work suggests that restored prairie populations likely face strong selection and that promoting the potential for adaptation in these systems may be necessary for restoring populations both now and in the face of further global change. 

Restoration in this era of climate change comes with a new challenge: anticipating how best to restore populations to persist under future climate conditions. Specifically, it remains unknown whether locally adapted or warm‐adapted seeds best promote native plant community restoration in the warmer conditions predicted in the future and whether local or warm‐adapted soil microbial communities could mitigate plant responses to warming. This may be especially relevant for biomes spanning large climatic gradients, such as the North American tallgrass prairie. Here, we used a short‐term mesocosm experiment to evaluate how seed provenances (Local Northern region, Non‐local Northern region, Non‐local Southern region) of 10 native tallgrass prairie plants (four forbs, two legumes, and four grasses) responded to warmer conditions predicted in the future and how soil microbial communities from those three regions influenced these responses. Warming and seed provenance affected plant community composition and warming decreased plant diversity for all three seed provenances. Plant species varied in their individual responses to warming, and across species, we detected no consistent differences among the three provenances in terms of biomass response to warming and few strong effects of soil provenance. Our work provides evidence that warming, in part, may reduce plant diversity and affect restored prairie composition. Because the southern provenance did not consistently outperform others under warming and we found little support for the “local is best” paradigm currently dominating restoration practice, identifying appropriate seed provenances to promote restoration success both now and in future warmer environments may be challenging. Due to the idiosyncratic responses across species, we recommend that land managers compare seeds from different regions for each species to determine which seed provenance performs best under warming and in restoration for tallgrass prairies.