The evolution of chemical complexity has been a major driver of plant diversification,with novel compounds serving as key innovations.The species-rich mint family (Lamiaceae) produces an enormous variety of compounds that act as attractants and defense molecules in nature and are used widely by humans as flavor additives,fragrances,and anti-herbivory agents.To elucidate the mechanisms by which such diversity evolved,we combined leaf transcriptome data from 48 Lamiaceae species and four outgroups with a robust phylogeny and chemical analyses of three terpenoid classes (monoterpenes,sesquiterpenes,and iridoids) that share and compete for precursors.Our integrated chemical-genomic-phylogenetic approach revealed that:(1) gene family expansion rather than increased enzyme promiscuity of terpene synthases is correlated with mono-and sesquiterpene diversity;(2) differential expression of core genes within the iridoid biosynthetic pathway is associated with iridoid presence/absence;(3) generally,production of iridoids and canonical monoterpenes appears to be inversely correlated;and (4) iridoid biosynthesis is significantly associated with expression of geraniol synthase,which diverts metabolic flux away from canonical monoterpenes,suggesting that competition for common precursors can be a central control point in specialized metabolism.These results suggest that multiple mechanisms contributed to the evolution of chemodiversity in this economically important family.