Does early season browsing influence the effect of self-pollination in scarlet gilia?

Herbivore damage can have indirect effects on plant fitness by influencing other important plant-animal interactions, such as pollination biology. For example, damage to floral and vegetative structures may influence the patt ern of pollen movement within and among individual plants. In obligately ou tcrossing species, enhanced movement of self pollen (geitonogamy) can negat ively impact fitness if self pollen clogs stigmas, interferes with stylar t ransmitting tracts, usurps ovules, or increases fruit abortion. We investig ated whether early season browsing affects the fitness cost of self-pollina tion in the obligately outcrossing species scarlet gilia, Ipomopsis aggrega ta, using clipping and emasculation treatments. We found that clipping significantly reduced the production of flowers, fru its, and seeds whereas emasculation significantly increased the production of these components of female fitness. In addition, we detected a significa nt interaction between the clipping and emasculation treatments when consid ering four components of fitness simultaneously; emasculation led to an inc rease in the fitness of unclipped plants but not clipped plants. We propose two nonexclusive mechanisms to explain this pattern. First, damaged plants may experience reduced self-pollination due to reductions in pollinator vi sitation or effectiveness. Alternatively, damaged plants may simply lack th e resources (or the ability to allocate resources) to benefit from emascula tion. Our results support the notion that herbivory can have indirect effec ts on plant fitness through effects on other plant-animal interactions.