Adaptive Transgenerational Plasticity through Priming in Response to Neighbor Density in Mimulus platycalyx

Transgenerational plasticity (TGP) allows organisms to epigenetically alter offspring phenotypes based on their own environmental experience. TGP is adaptive if offspring perform better when their conditions match those experienced by parents. TGP is now a well-established phenomenon in plants, with current research focusing on the range of environmental causes and the mechanisms that epigenetically translate environmental experiences into phenotypic responses. This study tests neighbor density as an environmental driver of TPG, either through induction (response determined only by parental experience) or priming (response determined by the combination of parental and offspring experience). Replicate individuals of a single genotype of Mimulus platycalyx were grown to maturity under three conditions: No neighbors, Medium neighbor density, or High neighbor density. Offspring produced by selfing plants within each parental treatment were grown under both crowded and uncrowded conditions and measured for height, plant size traits, and flower number. Offspring growing under crowded conditions were relatively taller, had bigger leaves, and produced more flowers if their parents experienced neighbor competition than if their parents did not. In contrast, offspring grown alone performed relatively better when their parents also grew alone and did not experience competition. This pattern of performance variation, where plants did best when their environmental conditions matched those of their parents, suggests adaptive transgenerational priming in this species.