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Abstract Despite multiple ecological and evolutionary hypotheses that predict patterns of phenotypic relationships between plant growth, reproduction and constitutive and/or induced resistance to herbivores, these hypotheses do not make any predictions about the underlying molecular genetic mechanisms that mediate these relationships.We investigated how divergent plant life‐history strategies in the yellow monkeyflower and a life‐history altering locus,DIV1, influence plasticity of phytochemical herbivory resistance traits in response to attack by two herbivore species with different diet breadth.Life‐history strategy (annual vs. perennial) and theDIV1locus significantly influenced levels of constitutive herbivory resistance, as well as resistance induction following both generalist and specialist herbivory. Perennial plants had higher total levels of univariate constitutive and induced defence than annuals, regardless of herbivore type. Annuals induced less in response to generalist herbivory than did perennials, while induction response was equivalent across the ecotypes for specialist herbivory.The effects of theDIV1locus on levels of constitutive and induced defence were dependent on genetic background, the annual versus perennial haplotype ofDIV1and herbivore identity. The patterns of univariate induction due toDIV1were non‐additive and did not always match expectations based on patterns of divergence for annual/perennial parents. For example, perennial plants had higher levels of constitutive and induced defence than did annuals, but when the annualDIV1was present in the perennial genetic background induction response to herbivory was higher than for the perennial parent lines.Patterns for multivariate defence arsenals generally echoed those of univariate, with annual and perennial monkeyflowers and those with alternative versions ofDIV1differing significantly in constitutive and induced resistance. Like univariate resistance, induced multivariate defence arsenals were affected by herbivore identity.Our results highlight the complexity of the genetic mechanisms underlying plastic response to herbivory. While a genetic locus underlying substantial phenotypic variation in life‐history strategy and constitutive defence also influences defence plasticity, the induction response also depends on genetic background. This result demonstrates the potential for some degree of evolutionary independence between constitutive and induced defence, or induced defence and life‐history strategy, in monkeyflowers. Read the freePlain Language Summaryfor this article on the Journal blog. 

Phytochemical defenses, plant-produced compounds that can deter or slow herbivores, are critical in influencing the interactions between herbivores and their host plants—some of the most diverse and abundant organisms on earth. We discuss the foundational findings and theories related to the direct defense of plants against herbivores by these compounds, as well as continuing research questions in this field. We highlight the costs associated with phytochemical defense production and variation within individual plants in the distribution of phytochemicals, both spatially and temporally. We then discuss coevolutionary theory and the adaptations of herbivores to cope with phytochemical defense compounds. Last, we delve into the incredible diversity of phytochemical compounds, the role of diversity in herbivory, and new ways of measuring and understanding phytochemical diversity. 

Colorado is home to an incredibly rich community of native pollinating insects that contribute to the state’s economy and enhance Coloradans’ quality of life through the irreplaceable role they play in ecosystems. The pollination services these essential insects provide are at the heart of a healthy environment, contributing to our agricultural production and food systems, and relied upon by flowering plants across the state. In turn, flowering plants support the state’s wildlife, add color to the beautiful landscapes that we all treasure, and provide the basis for healthy functioning ecosystems. Despite their central importance, however, to date, no comprehensive assessment of the health of the state’s native pollinating insects has been conducted. Recognizing this need for coordinated state-level efforts to better understand the status and health of our native pollinating insects, Senate Bill 22-199, the Native Pollinating Insects Protection Study, was passed by the State Legislature and signed into law by Governor Jared Polis in May 2022. The Colorado Department of Natural Resources subsequently commissioned this study, awarded to a collaborative team of pollinator researchers, managers, and conservationists. The study was coordinated by Colorado State University Extension, in collaboration with the Xerces Society for Invertebrate Conservation and the University of Colorado Museum of Natural History, and in cooperation with leading experts in native pollinating insect ecology, management, and conservation.