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For agriculturally important plants, pollination and herbivory are two ecological factors that play into the success of crop yields. Each is also important in natural environments where invasive plants and their effect on species interactions may alter the native ecology. The California Wild Radish (Raphanus sativus x raphanistrum), a hybrid derived from an agriculturally important crop and a nonnative cultivar, is common in California. Remarkably, it has recently replaced wild populations of both progenitor species. Experiments on phenotypic variation for petal color and anti-herbivore defenses suggest both pairs of polymorphisms are maintained as a result of pollinator- and herbivore-mediated natural selection. This species provides an opportunity to understand how natural selection shapes the evolution of ecologically important traits when traits are constrained by two opposing forces. Here we provide the genome assembly of the California Wild Radish displaying improvement to currently existing genomes for agronomically important crucifers. This genome sequence provides the tools to dissect the genomic architecture of traits related to herbivory and pollination using natural variation in the wild as well as the ability to infer demographic and selective history in the context of hybridization. Study systems like these will improve our understanding and predictions of evolutionary change for correlated traits.

Plant distributions can be limited by habitat-biased herbivory, but the proximate causes of such biases are rarely known. Distinguishing plant-centric from herbivore-centric mechanisms driving differential herbivory between habitats is difficult without experimental manipulation of both plants and herbivores. Here we tested alternative hypotheses driving habitat-biased herbivory in bittercress (Cardamine cordifolia), which is more abundant under shade of shrubs and trees (shade) than in nearby meadows (sun) where herbivory is intense from the specialist fly Scaptomyza nigrita. This system has served as a textbook example of habitat-biased herbivory driving a plant's distribution across an ecotone, but the proximate mechanisms underlying differential herbivory are still unclear. First, we found that higher S. nigrita herbivory in sun habitats contrasts sharply with their preference to attack plants from shade habitats in laboratory choice experiments. Second, S. nigrita strongly preferred leaves in simulated sun over simulated shade habitats, regardless of plant source habitat. Thus, herbivore preference for brighter, warmer habitats overrides their preference for more palatable shade plants. This promotes the sun-biased herbivore pressure that drives the distribution of bittercress into shade habitats.

For agriculturally important plants, pollination and herbivory are 2 ecological factors that play into the success of crop yields. Each is also important in natural environments where invasive plants and their effect on species interactions may alter the native ecology. The California Wild Radish (Raphanus sativus × raphanistrum), a hybrid derived from an agriculturally important crop and a nonnative cultivar, is common in California. Remarkably, it has recently replaced wild populations of both progenitor species. Experiments on phenotypic variation for petal color and antiherbivore defenses suggest both pairs of polymorphisms are maintained as a result of pollinator- and herbivore-mediated natural selection. This species provides an opportunity to understand how natural selection shapes the evolution of ecologically important traits when traits are constrained by 2 opposing forces. Here we provide the genome assembly of the California Wild Radish displaying improvement to currently existing genomes for agronomically important crucifers. This genome sequence provides the tools to dissect the genomic architecture of traits related to herbivory and pollination using natural variation in the wild as well as the ability to infer demographic and selective history in the context of hybridization. Study systems like these will improve our understanding and predictions of evolutionary change for correlated traits. [ABSTRACT FROM AUTHOR]