Comments on relationships between native seed preferences of shrub-steppe granivores and seed nutritional characteristics.

Kelrick et al. (1986) argued that seed preferences of desert granivores are strongly influenced by soluble carbohydrate contents of native seed species. They assumed that bitterbrush (Purshia tridentata) seeds are eaten in their entirety by rodents, but in fact these granivores eat only embryos of bitterbrush seeds. Embryos have a much lower percentage of soluble carbohydrate than whole bitterbrush seeds, and the correlation between preference and soluble carbohydrate content of seeds for six native species becomes non-significant when embryo values are substituted for whole-seed values.