FLOWERING IN MALES AND FEMALES OF A UTAH WILLOW, SALIX-RIGIDA AND EFFECTS ON GROWTH, TANNINS, PHENOLIC GLYCOSIDES AND SUGARS

We manipulated resource allocation to reproduction in male and female Salix rigida by removing reproductive buds before expansion, and female flowers before fruit initiation. We documented a significant difference between fruiting and flowering females. Fruiting females produced smaller shoots, fewer reproductive buds and had lower concentrations of salicortin and tannins than females in the flower-removal treatment. No effect of treatment on growth and secondary metabolites was detected among males. Female controls produced less shoot biomass and fewer reproductive buds than male controls. This suggests that total reproductive effort is greater and reproduction more resource-limited in females than in males. Female willows had higher concentrations of tannin (reproductive and basal shoots) and salicortin (reproductive buds and shoots and basal shoots). Differences of this type could be the proximate mechanism behind the common pattern of male willows suffering more from vertebrate herbivory than females. This study supports the assumption that allocation to reproduction during one season may reduce growth and future reproductive potential. In addition, fruiting reduces concentrations of secondary metabolites, some of which may be effective as defense against vertebrate herbivores.