Differences in dietary composition and preference maintained despite gene flow across a woodrat hybrid zone.

Ecotones, characterized by adjacent yet distinct biotic communities, provide natural laboratories in which to investigate how environmental selection influences the ecology and evolution of organisms. For wild herbivores, differential plant availability across sharp ecotones may be an important source of dietary-based selection.We studied small herbivore diet composition across a sharp ecotone where two species of woodrat, and . , come into secondary contact with one another and hybridize. We quantified woodrat dietary preference through trn metabarcoding of field-collected fecal pellets and experimental choice trials. Despite gene flow, parental and maintain distinct diets across this fine spatial scale, and across temporal scales that span both wet and dry conditions. maintained a more diverse diet, with (California coffeeberry) making up a large portion of its diet. maintains a less diverse diet, with (desert almond) comprising more than half of its diet. Both and are known to produce potentially toxic plant secondary compounds (PSCs), which should deter herbivory, yet these plants have relatively high nutritional value as measured by crude protein content. and consumed and , respectively, in greater abundance than these plants are available on the landscape-indicating dietary selection. Finally, experimental preference trials revealed that exhibited a preference for , while exhibited a relatively stronger preference for . We find that exhibit a generalist herbivore strategy relative to , which exhibit a more specialized feeding strategy in this study system.Our results suggest that woodrats respond to fine-scale environmental differences in plant availability that may require different metabolic strategies in order to balance nutrient acquisition while minimizing exposure to potentially toxic PSCs.