Abstract
Strong selective gradients such as those that exist at ecological boundaries often present animals with a sharp transition in various resources, including the availability of food. Yet little is known concerning how animals respond to abrupt shifts in resources, especially when gene flow may limit local adaptation. Here, we used DNA metabarcoding and untargeted metabolomics of fecal samples to begin characterizing the foraging ecology of two closely related rodents (Neotoma bryanti and N. lepida) across a sharp ecological boundary. We find abrupt transitions in diet and metabolomic signatures that coincide with the rapid habitat transition. Further, we show that individuals have habitat-specific diets that are dominated by distinctly toxic plants that likely require different metabolic processing. Our approach allows detailed characterization of diet and metabolic processing of food plants, which can provide evolutionary ecologists and wildlife biologists much needed insight into the nutritional and physiological ecology of the systems they study and manage.
Highlights
Strong selection across sharp ecological boundaries can produce or maintain patterns of adaptive divergence over small spatial scales, even in the presence of gene flow (Antonovics, 2006; Grahame et al, 2006; Rosenblum, 2006, reviewed in Richardson et al, 2014)
We confirmed that 12 of 15 hill samples were left by N. bryanti, and 10 of 13 flats samples were left by N. lepida
Using genetic analysis of fecal samples we show that woodrats occupying each side of this sharp ecotone largely consumed distinct sets of plants during our sampling period
Summary
Strong selection across sharp ecological boundaries can produce or maintain patterns of adaptive divergence over small spatial scales, even in the presence of gene flow (Antonovics, 2006; Grahame et al, 2006; Rosenblum, 2006, reviewed in Richardson et al, 2014). One of the main environmental factors to which they must respond at sharp habitat boundaries or in heterogeneous environments is food availability. Some of the primary diet-related adaptations in these herbivores, are likely associated with how these animals protect themselves metabolically from overexposure to plant toxins (Skopec et al, 2008; Forbey et al, 2018). Identifying how animals respond to changes in exposure to plant secondary compounds, spatially and temporally, will be critical in predicting how animals will respond to climate change, and the associated shifts in community composition and food availability (Estrada et al, 2016; Beale et al, 2018; Forbey et al, 2018)
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