A MINORITY OF STRAINS OF THE INSECT PATHOGENIC METARHIZIUM ROBERTSII (MR) ARE ROOT COLONIZING PLANT GROWTH PROMOTERS. IN THIS PROJECT WE WILL EXAMINE THE MECHANISMS BY WHICH A MICROBE'S INTERACTIONS WITH PLANTS CAN RAPIDLY EMERGE USING MOLECULAR AND EVOLUTIONARY APPROACHES. RAPID EVOLUTION IS A TRAIT SHARED WITH PATHOGENS, PESTS AND CANCERS; ALTHOUGH IN MOST CASES THE UNDERLYING MECHANISMS ARE POORLY UNDERSTOOD. ADDRESSING THESE MECHANISMS WITH MR, WHICH IS AN EXPERIMENTALLY VERY TRACTABLE MODEL SYSTEM, WILL INVOLVE ASKING MANY BASIC QUESTIONS ON POORLY UNDERSTOOD TOPICS THAT SPAN MUCH OF MOLECULAR EVOLUTION, SUCH AS THE RELATIVE IMPORTANCE OF AMINO-ACID VERSUS REGULATORY EVOLUTION. MOREOVER, UNDERSTANDING ECOLOGICAL DIVERSIFICATION IS PARTICULARLY CRUCIAL FOR PREDICTING THE OUTCOME OF FUNGAL RESPONSES TO CLIMATE CHANGE AND DISEASE OUTBREAKS. BY FOCUSING ON THE GENETIC BASIS OF RECENT ADAPTIVE CHANGES WE WILL ADDRESS THE UNCERTAINTY OF HOW INVASIVE STRAINS COULD INTERPLAY WITH THE BIOLOGICAL WORLD AND ADAPT TO A NEW NATURAL ENVIRONMENT. METARHIZIUM SPP ARE ALREADY DEPLOYED AS BIOLOGICAL INSECTICIDES, AND BY IDENTIFYING HOW THEY WORK AS PLANT SYMBIONTS, AND WHEN AND WHY THEY DO NOT, WE WILL FACILITATE THEIR USE IN AN EXPANDED ROLE AS COMPREHENSIVE PLANT GROWTH PROMOTERS. AS METARHIZIUM SPP ARE CLOSELY RELATED TO MANY IMPORTANT PLANT PATHOGENS AND BIOCONTROL FUNGI, WE EXPECT OUR RESULTS AND CONCLUSIONS TO HAVE MANY APPLICATIONS.