Factors Influencing Emerald Ash Borer Ecological Interactions

Abstract Emerald ash borer beetles ( Agrilus planipennis ) in North America are a destructive invasive species that increase tree mortality continent-wide, resulting in major ecological and economic impacts. Trees that are infested experience mortality rates which can exceed 99%, disrupting ecological communities and threatening the $218 billion forestry industry in North America. Given the ecological and economic impact of these pests, we seek to identify biological interactions and gain a better understanding of what ecological factors might influence these relationships. We use DNA metabarcoding from multiple markers to analyze the fungal, parasitic, plant, and microbial interactions of these beetles, and assess the relative importance of life stage (e.g., larvae, pupae, and adults), collection location, habitat, and date on the detection of ecological interactions. We detected 30 different taxonomic orders including 29 order-level interactions in larva1-stage individuals (3 animal, 17 bacteria, and 9 fungi), 64 in larva2-stage individuals (8 animal, 24 bacteria, and 32 fungi), 10 in larva3-stage individuals (2 animal, 3 bacteria, and 5 fungi), 74 in the pupae (5 animal, 31 bacteria, and 38 fungi), and 82 in the adult beetles (4 animal, 48 bacteria, 29 fungi, and 1 parasitic alveolate). These detections include several likely agents of biocontrol including the known commercially available Beauveria fungus, and several potential parasites including Wolbachia and ichneumonid wasps. A random forest model suggests the detection of interactions is best predicted by collection date and life stage, with interactions more likely to be detected in pupal samples which may be the ideal target for future analysis, where cost and time constraints prevent the more thorough analysis of all life stages.