Life history trait divergence among populations of a non-palatable species reveals strong non-trophic indirect effects of an abundant herbivore

When large herbivores exert selection on their prey plant species, co-occurring, non-prey species may experience selection through non-trophic indirect effects. Such selection is likely common where herbivores are overabundant. Yet, empirical studies of non-trophic indirect effects as drivers of non-prey trait evolution are lacking. Here we test for adaptive shifts in life history traits in an unpalatable species, Arisaema triphyllum, a common forest perennial that is unique because it exhibits size-dependent sex switching. We collected A. triphyllum from six sites that experience a gradient in abiotic stress caused by deer browse pressure on prey plant species that generate indirect effects. We grew A. triphyllum from these sites in a common garden for five years to evaluate life history predictions linking strong indirect effects and abiotic stress to changes in life history traits: flowering onset size threshold, female flowering size threshold, relative growth rate (RGR), biomass al...