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Intraspecific diversity of dominant species in native plant communities can modulate ecosystem function under both optimal and stressful conditions. Yet, few genotype by environment interaction studies quantify differences in the shape of plasticity functions or phenotypic breakpoints across genotypes in natural populations.

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During the 1930s Dust Bowl drought in the central United States, species with the C₃photosynthetic pathway expanded throughout C₄-dominated grasslands. This widespread increase in C₃grasses during a decade of low rainfall and high temperatures is inconsistent with well-known traits of C₃vs. C₄pathways. Indeed, water use efficiency is generally lower, and photosynthesis is more sensitive to high temperatures in C₃than C₄species, consistent with the predominant distribution of C₃grasslands in cooler environments and at higher latitudes globally. We experimentally imposed extreme drought for 4 y in mixed C₃/C₄grasslands in Kansas and Wyoming and, similar to Dust Bowl observations, also documented three- to fivefold increases in C₃/C₄biomass ratios. To explain these paradoxical responses, we first analyzed long-term climate records to show that under nominal conditions in the central United States, C₄grasses dominate where precipitation and air temperature are strongly related (warmest months are wettest months). In contrast, C₃grasses flourish where precipitation inputs are less strongly coupled to warm temperatures. We then show that during extreme drought years, precipitation–temperature relationships weaken, and the proportion of precipitation falling during cooler months increases. This shift in precipitation seasonality provides a mechanism for C₃grasses to respond positively to multiyear drought, resolving the Dust Bowl paradox. Grasslands are globally important biomes and increasingly vulnerable to direct effects of climate extremes. Our findings highlight how extreme drought can indirectly alter precipitation seasonality and shift ecosystem phenology, affecting function in ways not predictable from key traits of C₃and C₄species.

Grasslands of the central United States are expected to experience severe droughts and other climate extremes in the future, yet we know little about how these grasses will respond in terms of gene expression. We compared gene expression inAndropogon gerardiiandSorghastrum nutans, two closely related codominant C₄grasses responsible for the majority of ecosystem function, usingRNA‐seq. We compared Trinity assemblies within each species to determine annotated functions of transcripts responding to drought. Subsequently, we compared homologous annotated gene‐groups across the two species using cross‐species meta‐level analysis and functional clustering based on key terms. The majority of variation was found between species, as opposed to between drought and watered treatments. However, there is evidence for differential responses;Andropogonallocated gene expression differently compared toSorghastrum, suggestingAndropogonfocuses on stress alleviation (such as oxygen radical scavenging) rather than prevention. In contrast,Sorghastrummay employ a drought avoidance strategy by modulating osmotic response, especially with hormonal regulation. We foundSorghastrumtended to be more sensitive within 10 key gene‐groups related to stress, abscisic acid and trichomes, suggesting gene expression may mechanistically parallel sensitivity at the physiological level. Our findings corroborate phenotypic and physiological differences in the field and may help explain the phenotypic mechanisms of these two species in the tallgrass prairie community under future drought scenarios.

Global change forecasts in ecosystems require knowledge of within‐species diversity, particularly of dominant species within communities. We assessed site‐level diversity and capacity for adaptation inBouteloua gracilis, the dominant species in the Central US shortgrass steppe biome.

Climatic extremes, such as severe drought, are expected to increase in frequency and magnitude with climate change. Thus, identifying mechanisms of resilience is critical to predicting the vulnerability of ecosystems. An exceptional drought ( 

Random species loss has been shown experimentally to reduce ecosystem function, sometimes more than other anthropogenic environmental changes. Yet, controversy surrounds the importance of this finding for natural systems where species loss is non‐random.