The North American boreal forest is a massive ecosystem, and its keystone herbivore is the snowshoe hare (Lepus americanus). Hares are exposed to considerable environmental extremes in diet and weather, food availability, and predation risk. Gut microbiomes have been suggested to facilitate adaptive animal responses to environmental change, but severe environmental challenges to homeostasis can also disrupt host-microbiome relationships. To better understand gut microbiome contributions to animal acclimation, we studied the fecal bacterial microbiome of wild hares across two types of extreme environmental change that are integral to their natural history: (1) seasonal transitions between summer and winter, and (2) changes over the ~10 year “boom-bust” population cycles that are characterized by shifting food resource availability and predation pressure. When compared to summer, hares in winter had lower bacterial richness and were depleted in twenty families (including Oxalobacteraceae and Christensenellaceae) but enriched for Ruminococcaceae (a family which contains plant fibre degrading microbiota) alongside nine other bacterial groups. Marked bacterial microbiome differences also occurred across phases of the population cycle. Bacterial microbiomes were lower in richness and compositionally distinct in the peak compared to the increase or decline phases of the population cycle. Direct measures of host physiology and diet quality (fecal fibre contents) most strongly supported food resource availability as a mechanism underlying phase-based differences in bacterial communities, but fecal fibre contents could not fully account for bacterial microbiome variation across phases.

Plant secondary metabolites (PSMs) are produced by plants to overcome environmental challenges, both biotic and abiotic. We were interested in characterizing how autumn seasonality in temperate and subtropical climates affects typical PSM production in comparison to herbivory. Herbivory is commonly measured from spring to summer when plants have high resource availability and are prioritizing growth and reproduction. However, autumn seasonality also challenges plants as they cope with limited resources and prepare survival for winter. This suggests a potential gap in knowledge on how autumn seasonality affects PSM production differently from herbivory. Using meta-analysis, we recorded production of 22 different PSM subgroups from 58 published papers to detect a typical response across all PSMs. We also compared production of five phenolic subgroups – hydroxybenzoic acids, flavan-3-ols, flavonols, hydrolysable tannins, and condensed tannins. We calculated effect sizes from herbivory studies (absence to presence) and temperate to subtropical seasonal studies (summer to autumn), while considering other variables (e.g., plant type, increase in time since herbivory, temperature, and precipitation). We did not detect a shared effect of herbivory or season on PSM production across all subgroups. However, we discovered herbivory having a positive effect on flavonol production and autumn seasonality having a positive effect on flavan-3-ol and condensed tannin production. We discuss how these responses might stem from three factors: 1. some PSMs are constitutively produced by plants in autumn whereas others are induced only following herbivory, 2. plants produce metabolites with higher costs only during seasons when other resources for growth and reproduction are less available, and 3. some PSM subgroups serve more than one function for plants and such functions can be season dependent. The outcome of our meta-analysis is that autumn seasonality changes PSM production differently from herbivory, and we see value in further investigating seasonality-herbivory interactions with plant chemical defense.

Plant secondary metabolites (PSMs) are produced by plants to overcome environmental challenges, both biotic and abiotic. We were interested in characterizing how autumn seasonality in temperate and subtropical climates affects typical PSM production in comparison to herbivory. Herbivory is commonly measured from spring to summer when plants have high resource availability and are prioritizing growth and reproduction. However, autumn seasonality also challenges plants as they cope with limited resources and prepare survival for winter. This suggests a potential gap in knowledge on how autumn seasonality affects PSM production differently from herbivory. Using meta-analysis, we recorded production of 22 different PSM subgroups from 58 published papers to detect a typical response across all PSMs. We also compared production of five phenolic subgroups – hydroxybenzoic acids, flavan-3-ols, flavonols, hydrolysable tannins, and condensed tannins. We calculated effect sizes from herbivory studies (absence to presence) and temperate to subtropical seasonal studies (summer to autumn), while considering other variables (e.g., plant type, increase in time since herbivory, temperature, and precipitation). We did not detect a shared effect of herbivory or season on PSM production across all subgroups. However, we discovered herbivory having a positive effect on flavonol production and autumn seasonality having a positive effect on flavan-3-ol and condensed tannin production. We discuss how these responses might stem from three factors: 1. some PSMs are constitutively produced by plants in autumn whereas others are induced only following herbivory, 2. plants produce metabolites with higher costs only during seasons when other resources for growth and reproduction are less available, and 3. some PSM subgroups serve more than one function for plants and such functions can be season dependent. The outcome of our meta-analysis is that autumn seasonality changes PSM production differently from herbivory, and we see value in further investigating seasonality-herbivory interactions with plant chemical defense.

Habitat disturbance, a common consequence of anthropogenic land use practices, creates human-animal interfaces where humans, wildlife, and domestic species can interact. These altered habitats can influence host-microbe dynamics, leading to potential downstream effects on host physiology and health. Here, we explored the effect of ecological overlap with humans and domestic species and infection with the protozoan parasite Giardia duodenalis on the bacteria of black and gold howler monkeys (Alouatta caraya), a key sentinel species, in northeastern Argentina. Fecal samples were screened for Giardia duodenalis infection using a nested PCR reaction, and the gut bacterial community was characterized using 16S rRNA gene amplicon sequencing. Habitat type was correlated with variation in A. caraya gut bacterial community composition but did not affect gut bacterial diversity. Giardia presence did not have a universal effect on A. caraya gut bacteria across habitats, perhaps due to the high infection prevalence across all habitats. However, some bacterial taxa, such as Actinobacteria, Bacteroidetes, Firmicutes, and Lachnospiraceae, were found to vary with Giardia infection. While A. caraya’s behavioral plasticity and dietary flexibility allow them to exploit a range of habitat conditions, habitats are generally becoming more anthropogenically disturbed, and thus, less hospitable. Alterations in gut bacterial community dynamics are one possible indicator that A. caraya may be reaching its physiological limits for plasticity since changes in host-microbe relationships due to stressors from habitat disturbance may lead to negative repercussions for host health. These dynamics are likely relevant for understanding organism responses to environmental change in other mammals.