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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. 

Forbs comprise most of the plant diversity in North American tallgrass prairie and provide vital ecosystem services, but their abundance in prairie restorations is highly variable. Restoration practitioners typically sow C₄grasses in high abundances because they are inexpensive, provide fuel for prescribed fires, can dominate reference sites, and suppress weeds that suppress sown forbs. However, C₄grasses can also suppress sown forbs, calling this practice into question. We evaluated how C₄grasses influence the abundance and diversity of sown forbs in 78 restored prairies across Illinois, Indiana, and Michigan. We found that the direct negative effects of C₄grasses on sown forbs outweighed indirect positive effects that occurred as C₄grasses suppressed nonsown species, which in turn suppressed sown forbs. This pattern was especially strong for the C₄grass big bluestem (Andropogon gerardii). Therefore, strategies to promote big bluestem and other C₄grasses would not promote sown forbs. Although C₄grass cover was not strongly related to two hypothesized drivers (time since fire or site age), seeding density of C₄grasses increased their cover. Sown forb cover also increased with forb seeding density, increased indirectly with fire (through its negative effect on nonsown species), and decreased indirectly with soil water‐holding capacity (through its positive effect on nonsown species). These results highlight the complex interplay of species groups during grassland restoration and show how managers can promote sown forbs in restored prairies: increasing forb seeding density and reducing time since fire and the abundance of C₄grasses and weeds.

 

There is strong evidence for a positive relationship between biodiversity and ecosystem functioning at local spatial scales. However, how different aspects of biodiversity relate to multiple ecosystem functions (multifunctionality) across heterogeneous landscapes, and how the magnitude of biodiversity, dominant species, and environmental effects on functioning compare, remain poorly understood. We compared relationships between plant phylogenetic, functional, and taxonomic diversity and ecosystem multifunctionality across 29 restored grasslands. Functional diversity was positively associated with multifunctionality, more strongly than other diversity measures; however, landscape composition explained nearly four times more variation in multifunctionality than did functional diversity, with plots within human‐modified landscapes supporting lower multifunctionality. Individual functions were typically more strongly correlated with environmental variables than with diversity. We also found that abundance of the dominant species,Andropogon gerardii, was positively correlated with multifunctionality. Plant diversity, dominant species, and underlying environmental conditions underpin ecosystem multifunctionality in grasslands, but how biodiversity is measured matters for the strength and direction of biodiversity–ecosystem function relationships. Finally, in natural systems environmental variation unrelated to local biodiversity is important for determining ecosystem functioning.