CENTRAL GRASSLANDS ACCOUNT FOR $6 BILLION IN AGRICULTURAL PRODUCTION IN KS ANNUALLY AND ARE DOMINATED BY THE FORAGE GRASS BIG BLUESTEM, ANDROPOGON GERARDII. THE MIDWEST HAS RECENTLY EXPERIENCED DROUGHT AND FUTURE CHANGES IN PRECIPITATION WILL IMPACT PRODUCTIVITY AND SUSTAINABILITY OF RANGELANDS. OUR GOAL IS TO CHARACTERIZE PHENOTYPIC AND GENETIC VARIATION OF A. GERARDII IN DROUGHT TOLERANCE TRAITS AND BIOMASS YIELD ACROSS THE RANGE, THEN MODEL CHANGES IN GENOTYPE AND PHENOTYPE WITH INCREASED TEMPERATURE AND DROUGHT. OUR RESEARCH PLATFORM INCLUDES NEW RAINOUT SHELTERS COMPLEMENTED BY A CHARACTERIZATION OF PHENOTYPES, GENOTYPES, AND TRANSCRIPTOMES FROM GEOGRAPHICALLY DIVERSE POPULATIONS ACROSS THE GREAT PLAINS. SPECIES DISTRIBUTION MODELS WILL BE DEVELOPED TO PREDICT CHANGES IN GENOTYPE AND PHENOTYPE UNDER CURRENT AND FUTURE SCENARIOS. THIS RENEWED FOCUS ENHANCES OUR PREVIOUS RECIPROCAL GARDEN WORK BASED ON A NARROW CROSS-SECTION OF THE GREAT PLAINS (IL TO KS), PROVIDING RESULTS ACROSS BROADER CLIMATE GRADIENTS. OBJECTIVES ARE TO: 1) CHARACTERIZE PHENOTYPES AND GENOTYPES FROM 44 GEOGRAPHICALLY DIVERSE POPULATIONS ACROSS THE GREAT PLAINS CLIMATE GRADIENTS, 2) CHARACTERIZE GENE EXPRESSION DIFFERENCES FROM A) PHENOTYPICALLY DIVERGENT MESIC AND XERIC ECOTYPES IN RESPONSE TO EXPERIMENTAL RAINFALL DROUGHT IN LONG-TERM RECIPROCAL GARDEN AND B) IN GREENHOUSE DROUGHT MANIPULATIONS USING POPULATIONS FROM ACROSS THE GEOGRAPHIC RANGE, 3) LINK TRANSCRIPTOME EXPRESSION AND GENOTYPE DIFFERENCES TO BIOMASS, ECOPHYSIOLOGICAL RESPONSES OF DIVERGENT ECOTYPES TO ALTERED RAINFALL AND 4) MODEL CURRENT AND FUTURE GENOTYPES AND PHENOTYPES TO TEMPERATURE AND PRECIPITATION USING MODIFIED SPECIES DISTRIBUTION MODELS. THIS RESEARCH WILL PROVIDE INFORMATION ON RESPONSE TO DROUGHT IN ECOTYPES OF GEOGRAPHICALLY DIVERSE BIG BLUESTEM AND IDENTIFY CANDIDATE GENES ASSOCIATED WITH DROUGHT TOLERANT TRAITS. WE WILL USE THESE DATA AS INPUT TO MODELS TO PREDICT HOW THESE VITAL RANGELANDS MAY CHANGE WITH PREDICTED HIGHER TEMPERATURES AND DROUGHT. THESE STUDIES WILL ALLOW US TO RECOMMEND CLIMATE-MATCHED ECOTYPES FOR RESTORATION IN CHANGING CLIMATES. THE RESEARCH DIRECTLY ALIGNS WITH THE GOALS OF THE USDA NIFA FOUNDATIONAL PROGRAM-PHYSIOLOGY, AS IT WILL IDENTIFY GENETIC AND PHYSIOLOGICAL MECHANISMS THAT CONTRIBUTE TO DROUGHT RESPONSE IN THE GREAT PLAINS.