Intraspecific trait variation has important ecological and evolutionary consequences that cause individuals within populations to differ in traits and interactions with associated communities. Here we characterize two axes of plant genetic variation – genotypic vs. sexual dimorphic – in plant traits and trait plasticity, and the consequences of such trait variation for associated herbivore communities. To do so, we performed a two-year field experiment with male and female genotypes of the dioecious shrub Baccharis salicifoliaunder ambient and increased precipitation. Twenty male and twenty female cuttings were collected from a wild-grown population and planted within a nearby common garden under and ambient and increased precipitation. We assessed plant growth, terpene concentration, specific leaf area (SLA), percent water, percent nitrogen leaf toughness, water use efficiency, flower number, and resistance to herbivores.
Results/Conclusions
We found that plant traits showed significant genotypic variation in all traits with the exception of terpenes. Plant sex did not influence terpenes, SLA, and percent water plasticity. Precipitation increased plant growth by 10-15%. In addition, precipitation and genotype interacted to influence growth and terpene concentration, suggesting that there is genetic variation and plasticity in growth and terpene concentrations in response to precipitation. Herbivore resistance and plasticity was not influenced by plant genotype, sex, or precipitation. Water use efficiency had a marginal effect on overall resistance to herbivores. These results suggest that genetic variation and gender influence plant trait variation and plasticity for some traits of ecological importance for higher trophic levels under altered environmental conditions.