Does Inbreeding Affect Tolerance to Inflorescence Damage in Mimulus guttatus?

Inbreeding in plants causes various declines in fitness estimates across many species and may also affect adaptive phenotypic plasticity, as observed in tolerance to herbivory. Although there are a growing number of studies looking at this effect, there are still not enough to make general conclusions about the relationship between homozygosity and tolerance or resistance. In this work, we examined whether drastic herbivory, destruction of the flowering apex, was affected by inbreeding in three populations of Mimulus guttatus. We found that inbreeding increased tolerance to simulated herbivory in one population, had no effect on tolerance in another, and decreased tolerance in a third. These results point to the importance of the underlying genetic histories of individual populations, which are the fodder for the action of inbreeding. It may be difficult to find consistent effects of inbreeding on plastic traits like tolerance because of the relatively unpredictable relationship between heterozygosity and plasticity in general.