Response to artificial selection on a heritable, environmentally induced defense in Mimulus guttatus (Yellow Monkeyflower)

Environmental stress can affect transcription of genes through reversible modifications to the structure of DNA. These epigenetic modifications do not affect the nucleotide sequence, but they can be inherited in the offspring or grand-offspring in specific species. Genes in Mimulus guttatus may be epigenetically altered in response to damage from insects, affecting production of trichomes (sticky defensive hairs on the leaves) in the next generation. Higher trichome production protects against insects, possibly allowing for higher reproductive success in the presence of herbivorous insects. To determine the precise mechanisms through which this phenomenon occurs, we conducted an artificial selection experiment. One population of Mimulus guttatus was selected for a high increase in trichome density in response to damage. Another population was selected for high baseline trichome density. Both selective regimes were replicated. Selection experiments have produced plant populations with dense trichomes and separate populations with high responsiveness in the number of trichomes, indicating the possibility for evolution in these traits. One future study will quantify the ability to transmit this response to future generations. Plant lines with extreme adaptations will be grown in field to determine if their trichome production patterns are adaptive. These results could enhance our understanding of the mechanisms and evolutionary consequences of inheritance of an induced defense