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

   https://doi.org/10.1111/mec.15431  

   Orr, Teri J. ; Kitanovic, Smiljka ; Schramm, Katharina M. ; Skopec, Michele M. ; Wilderman, P. Ross ; Halpert, James R. ; Dearing, M. Denise ( April 2020 , Molecular Ecology)

   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 plant secondary metabolites (PSMs), which may exceed the animal's detoxification capacities. Theory predicts that specialists will have unique detoxification mechanisms to process high levels of dietary toxins. To evaluate this hypothesis, we compared liver microsomal metabolism of a juniper specialist,Neotoma stephensi(diet >85% juniper), to a generalist,N. albigula(diet ≤30% juniper). Specifically, we quantified the concentration of a key detoxification enzyme, cytochrome P450 2B (CYP2B) in liver microsomes, and the metabolism of α‐pinene, the most abundant terpene in the juniper species consumed by the specialist woodrat. In both species, a 30% juniper diet increased the total CYP2B concentration (2–3×) in microsomes and microsomal α‐pinene metabolism rates (4‐fold). InN. stephensi, higher levels of dietary juniper (60% and 100%) further induced CYP2B and increased metabolism rates of α‐pinene. Although no species‐specific differences in metabolism rates were observed at 30% dietary juniper, total microsomal CYP2B concentration was 1.7× higher inN. stephensithan inN. albigula(p < .01), suggestingN. stephensiproduces one or more variant of CYP2B that is less efficient at processing α‐pinene. InN. stephensi, the rates of α‐pinene metabolism increased with dietary juniper and were positively correlated with CYP2B concentration. The ability ofN. stephensito elevate CYP2B concentration and rate of α‐pinene metabolism with increasing levels of juniper in the diet may facilitate juniper specialization in this species.

    

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2. CHROMOSOME EVOLUTION IN WOODRATS, GENUS NEOTOMA (RODENTIA: CRICETIDAE)

   https://doi.org/10.1111/j.1558-5646.1976.tb00892.x  

   Mascarello, J. T. ; Hsu, T. C. ( March 1976 , Evolution)
3. Hybridization in the absence of an ecotone favors hybrid success in woodrats ( Neotoma spp.)

   https://doi.org/10.1093/evolut/qpad012  

   Klure, Dylan M. ; Greenhalgh, Robert ; Parchman, Thomas L. ; Matocq, Marjorie D. ; Galland, Lanie M. ; Shapiro, Michael D. ; Dearing, M. Denise ( January 2023 , Evolution)

   Hybridization is a common process that has broadly impacted the evolution of multicellular eukaryotes; however, how ecological factors influence this process remains poorly understood. Here, we report the findings of a 3-year recapture study of the Bryant’s woodrat (Neotoma bryanti) and desert woodrat (Neotoma lepida), two species that hybridize within a creosote bush (Larrea tridentata) shrubland in Whitewater, CA, USA. We used a genotype-by-sequencing approach to characterize the ancestry distribution of individuals across this hybrid zone coupled with Cormack–Jolly–Seber modeling to describe demography. We identified a high frequency of hybridization at this site with ~40% of individuals possessing admixed ancestry, which is the result of multigenerational backcrossing and advanced hybrid-hybrid crossing. F1, F2, and advanced generation hybrids had apparent survival rates similar to parental N. bryanti, while parental and backcross N. lepida had lower apparent survival rates and were far less abundant. Compared to bimodal hybrid zones where hybrids are often rare and selected against, we find that hybrids at Whitewater are common and have comparable survival to the dominant parental species, N. bryanti. The frequency of hybridization at Whitewater is therefore likely limited by the abundance of the less common parental species, N. lepida, rather than selection against hybrids.

    

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4. Ambient temperature-mediated changes in hepatic gene expression of a mammalian herbivore ( Neotoma lepida )

   https://doi.org/10.1111/mec.14192  

   Connors, Patrice Kurnath ; Malenke, Jael R. ; Dearing, M. Denise ( June 2017 , Molecular Ecology)
5. Metabolomic evidence of independent biotransformation pathways for terpenes in two specialist mammalian herbivores (genus Neotoma )

   https://doi.org/10.1111/1749-4877.12734  

   SCHRAMM, Katharina ; SKOPEC, Michele ; DEARING, Denise ( June 2023 , Integrative Zoology)

   Herbivory is common in mammals, yet our understanding of detoxification processes used by mammals to biotransform plant secondary compounds (PSCs) is limited. Specialist herbivores are thought to have evolved detoxification mechanisms that rely more heavily on energetically cheap Phase I biotransformation reactions to process high levels of PSCs in their diets. We explored this hypothesis by comparing the urinary metabolite patterns of two specialist herbivores (genusNeotoma).Neotoma stephensiis an obligate specialist on one‐seeded juniper (Juniperus monosperma).Neotoma lepidais a generalist forager across its range, yet populations in the Great Basin specialize on Utah juniper (J. osteosperma). While both juniper species have high levels of terpenes, the terpene profiles and quantities differ between the two. Individuals from both woodrat species were fed diets of each juniper in a cross‐over design. Urine, collected over a 24‐h period, was extracted and analyzed in an untargeted metabolomics approach using both GC‐MS and HPLC‐MS/MS. The obligate specialistN. stephensiexcreted a unique pattern of Phase I metabolites when fed its native juniper, whileN. lepidaexcreted a unique pattern of Phase II metabolites when fed its native juniper. Both woodrat species utilized the Phase II metabolic pathway of glucuronidation more heavily when consuming the more chemically diverseJ. osteosperma, andN. stephensiutilized less glucuronidation thanN. lepidawhen consumingJ. monosperma. These results are consistent with the hypothesis that obligate specialists may have evolved unique and efficient biotransformation mechanisms for dealing with PSCs in their diet.

    

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