Plant-herbivore interactions: Insect induced changes in host plant sex expression and fecundity.

We investigated changes in the reproduction of Pastinaea sativa which result in compensatory reproduction when herbivore feeding destroys the first infloresence produced. Late developing infloresences of damaged plants produce more flowers and a greater proportion of hermaphroditic flowers than late developing infloresences of control plants. In damaged plants the proportion of hermaphroditic flowers producing seeds in late developing infloresences also increases. These effects are due to the mechanical damage resulting from larval feeding. The herbivore acts as a mediator in a number of important plant processes affecting fecundity, including expression of sex.