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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. Microbiome stability and structure is governed by host phylogeny over diet and geography in woodrats ( Neotoma spp.)

   https://doi.org/10.1073/pnas.2108787118  

   Weinstein, Sara B. ; Martínez-Mota, Rodolfo ; Stapleton, Tess E. ; Klure, Dylan M. ; Greenhalgh, Robert ; Orr, Teri J. ; Dale, Colin ; Kohl, Kevin D. ; Dearing, M. Denise ( November 2021 , Proceedings of the National Academy of Sciences)

   The microbiome is critical for host survival and fitness, but gaps remain in our understanding of how this symbiotic community is structured. Despite evidence that related hosts often harbor similar bacterial communities, it is unclear whether this pattern is due to genetic similarities between hosts or to common ecological selection pressures. Here, using herbivorous rodents in the genusNeotoma, we quantify how geography, diet, and host genetics, alongside neutral processes, influence microbiome structure and stability under natural and captive conditions. Using bacterial and plant metabarcoding, we first characterized dietary and microbiome compositions for animals from 25 populations, representing seven species from 19 sites across the southwestern United States. We then brought wild animals into captivity, reducing the influence of environmental variation. In nature, geography, diet, and phylogeny collectively explained ∼50% of observed microbiome variation. Diet and microbiome diversity were correlated, with different toxin-enriched diets selecting for distinct microbial symbionts. Although diet and geography influenced natural microbiome structure, the effects of host phylogeny were stronger for both wild and captive animals. In captivity, gut microbiomes were altered; however, responses were species specific, indicating again that host genetic background is the most significant predictor of microbiome composition and stability. In captivity, diet effects declined and the effects of host genetic similarity increased. By bridging a critical divide between studies in wild and captive animals, this work underscores the extent to which genetics shape microbiome structure and stability in closely related hosts.

    

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4. 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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5. 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)