Strategies in herbivory by mammals revisited: The role of liver metabolism in a juniper specialist ( Neotoma stephensi ) and a generalist ( Neotoma albigula )

Although herbivory is widespread among mammals, few species have adopted a strategy of dietary specialization. Feeding on a single plant species often exposes herbivores to high doses of similar plant secondary metabolites (PSMs), which may exceed the animal’s detoxification capacities. Therefore, theory predicts that specialists will have unique detoxification mechanisms to process high levels of dietary toxins. To evaluate this hypothesis, we compared liver metabolism of a juniper specialist, Neotoma stephensi (diet >85% juniper), to that of a sympatric generalist, N. albigula (diet ≤30% juniper). Specifically, we quantified the content of a key detoxification enzyme, cytochrome P450 2B (CYP2B) in liver microsomes, as well as the microsomal turnover of α-pinene, the most abundant terpene in the juniper species consumed by the specialist woodrat. In both Neotoma species, a 30% juniper diet increased CYP2B content (2-3x) and α-pinene turnover rates (4-fold). In N. stephensi, higher l...