COMPENSATORY RESPONSE OF 2 DUNE ANNUALS TO SIMULATED BROWSING AND FRUIT PREDATION

Greenhouse and field studies were conducted to determine the effects of artificial fruit removal and clipping (simulated deer browsing) on components of reproduction of two indeterminate dune annuals: Cakile edentula var. lacustris (Bigel.) Hook and Corispermum hyssopifolium L. The results showed that both species were able to partially or completely compensate or even overcompensate for low to moderate levels of clipping or fruit removal only if the damage occurred in the early stages of fruit development. The indeterminate habit of growth of both species facilitated their compensatory ability. The removal of fruits and clipping of plants which mimick browsing by white tailed deer along Lake Huron resulted in a significant increase in their period of flowering and fruiting, especially in the early stages of fruit development. The plants compensated for fruit loss by increasing the number of fruits per plant. A delay in fruit removal or clipping to later stages of fruit maturation of both species drastically reduced reproduction. Similar experiments in the field revealed that, although the critical periods during which the plants were most susceptible were the same, the plants had lower compensatory ability. Fruit damage and clipping generally did not affect the seed mass of both species.