The Effect of Herbivory on the Mating System of Congeneric Native and Exotic Lespedeza Species

Abstract

For cleistogamous species, herbivory can affect a plant's mating system by altering the total amount of resources allocated to selfed (e.g., cleistogamous) and outcrossed (e.g., chasmogamous) seeds. Because exotic species are hypothesized to experience lower amounts of herbivory (enemy release), their mating system expression may differ from their native congeners. I examine the effect of herbivory on the mating systems of two co‐occurring congeneric species, Lespedeza cuneata and Lespedeza virginica, via a herbivory reduction experiment. The exotic species L. cuneata experienced 50% lower ambient levels of herbivory than its native congener L. virginica. Under natural herbivory levels, the proportion of chasmogamous seed produced was lower for the invasive L. cuneata than for the native L. virginica. Across an experimentally extended herbivory gradient, these two species had mating system responses that were directionally similar; as herbivory decreased, the proportion of chasmogamous seed produced for b...