FORESTS PROVIDE SUBSTANTIAL BENEFITS TO SOCIETY. THESE INCLUDE BENEFITS THAT ARE DIRECTLY QUANTIFIABLE -- FOR EXAMPLE, ECONOMIC BENEFITS SUCH AS TIMBER AND BIOMASS PRODUCTION AS WELL AS AESTHETIC BENEFITS SUCH AS AS NATIONAL PARK VISITS. THEY ALSO INCLUDE BENEFITS THAT ARE HARDER TO QUANTIFY -- ECOSYSTEM SERVICES SUCH AS ATMOSPHERIC CO2FIXATION AND PROVISION OF WILDLIFE HABITAT. HOWEVER, OUR FORESTS ARE UNDER THREAT. CLIMATE CHANGE HAS CAUSED WIDESPREAD MORTALITY IN FOREST TREES DUE IN LARGE PART TO SHIFTING DISTRIBUTIONS OF FUNGAL PATHOGENS. DISEASE EXPRESSION AND SEVERITY ARE ALSO LIKELY TO RESPOND DRAMATICALLY TO CHANGES IN CLIMATE. PLANT PATHOGENS --IN FORESTS AS WELL AS AGRICULTURAL SYSTEMS --ARE STRONGLY INFLUENCED BY ENVIRONMENTAL CONDITIONS, MAKING PATHOGEN CLIMATE-RESPONSE AN INTEGRAL COMPONENT OF FOREST MANAGEMENT.A CLEARER UNDERSTANDING OF ADAPTIVE RESPONSES AMONG FOREST PATHOGENS IS KEY TO IMPROVING PREDICTIVE MODELING AND TO INFORMING POTENTIAL MITIGATION STRATEGIES. FOR EXAMPLE, CURRENT MODELS OF FUTURE SPECIES DISTRIBUTIONS DO NOT GENERALLY ACCOUNT FOR POTENTIAL ADAPTATION TO CLIMATE. MITIGATION STRATEGIES WOULD ALSO BENEFIT FROM AN EVOLUTIONARY PERSPECTIVE -- FOR EXAMPLE, SILVICULTURAL TREATMENTS TO MITIGATE TREE STRESS AND TO ALTER FOREST MICROCLIMATE TO DISCOURAGE INFECTION AND SPREAD. THIS PROJECT WILL PROVIDE NEW INFORMATION ON RATES OF GENE FLOW, PATTERNS OF ADAPTIVE GENETIC DIVERSITY, AND THE TARGETS OF NATURAL SELECTION ACROSS THE GEOGRAPHIC RANGE OF TWO IMPORTANT FOREST PATHOGENS. THE PRIMARY OBJECTIVE OF THIS RESEARCH ARE TO 1) IDENTIFY CANDIDATE LOCI FOR CLIMATE ADAPTATION IN THE FUNGAL PATHOGENS INVOLVED IN BEECH BARK DISEASE (BBD), 2) ASSESS GENOTYPE EFFECTS ON FITNESS USING CULTURE GROWTH ASSAYS, AND 3) IDENTIFY CLIMATE ADAPTATION POTENTIAL IN DIVERSE FUNGI USING META-ANALYSIS.THUS, THEPROPOSED RESEARCH WILL INFORM FOREST DISEASE MANAGEMENT BY INCORPORATING EVOLUTIONARY KNOWLEDGE TO BETTER PREDICT PATHOGEN DISTRIBUTIONS UNDER DIFFERENT CLIMATE CHANGE SCENARIOS.FURTHER, THE TWO PATHOGENS STUDIED HERE HAVE CONTRASTING CLIMATE ASSOCIATIONS (WARMERVERSUSCOOLER TEMPERATURES), AND CO-INFECTION OF TREES BY THESE PATHOGENS IS ASSOCIATED WITH ELEVATED DISEASE SEVERITY AND TREE CANOPY DIEBACK. CO-INFECTION BY PATHOGENS THAT ARE ADAPTED TO A BROAD RANGE OF CLIMATIC CONDITIONS MAY CONTRIBUTE TO DISEASE AGGRESSIVENESS.QUANTIFYING LOCAL TEMPERATURE ADAPTATION WILL CONTRIBUTE TO A GROWING BODY OF KNOWLEDGE ON HOW TEMPERATURE ADAPTATION IN PATHOGEN ASSEMBLAGES INFLUENCES DISEASE EXPRESSION, THUS INFORMING POTENTIAL MITIGATION STRATEGIES.