“…Field studies of soil nutrient effects on resins of Copaifera, in comparative studies with Hymenaea, likewise showed no statistically significant effects on composition, but that increased availability of nitrogen decreased the yield (82-83)-as had been discovered in studies of monoterpenes (e.g., 84). Therefore, tree-to-tree intrapopulational as well as interpopulational compositional variation apparently could be significant in defense against foliovores and pathogens and hence may be due, in part, to biotic selection pressures (4,(85)(86), i.e., the trees with resin composition that successfully defends the tree survive whereas those with other composition do not. This represents a part of the co-evolution of the tree and its herbivores and pathogens.…”