Fecal microbiota and diet compositions of muskox female adults and calves

Gut microbiome is vertically transmitted by maternal lactation at birth in mammals. In this study, we investigated the gut microbiome and diet compositions of muskox, a large herbivore in the high Arctic. From muskox feces in Ella Island, East Greenland, we compared the microbiota composition using bacterial 16S rRNA gene sequencing and the dietary compositions of six female adults and four calves have been compared. Firmicutes was the most abundant bacterial phylum in both adults and calves, comprising 94.36% and 94.03%, respectively. There were significant differences in the relative abundance of two Firmicutes families: the adults were mainly dominated by Ruminococcaceae (73.90%), while the calves were dominated by both Ruminococcaceae (56.25%) and Lachnospiraceae (24.00%). Stable isotope analysis on the feces and eight referential plant samples in the study area showed that both adults and calves had similar ranges of 13C and 15N, possibly derived from the dominant diet plants of Empetrum nigrum and Salix glauca. Despite the similar diets, the different gut microbiome compositions in muskox adults and calves indicate that the gut microbiome of the calves may not be fully colonized yet as much as the one of the adults.

Batesian mimicry in plants: The significance of shared leaf shape between Alseuosmia pusilla and Pseudowintera colorata

<p>There is an immense amount of variation in leaf shape, size, and colouration, both across and within plant species. Leaf shape and colour, in some instances, can be attributed as a physiological response to particular abiotic stressors. However, leaf shape, size, and colour are used by herbivores to identify sources of palatable foliage for food. It is possible, therefore, that an undefended plant might gain protection from herbivores by matching leaf characteristics of a chemically defended species. The matching of defensive signals by an undefended species in order to dupe a predator is known as Batesian mimicry, and whilst believed to be a relatively common phenomenon amongst animals, it has yet to be proven in plants. The foliage of Alseuosmia pusilla (Colenso) A. Cunningham, is strikingly similar to the human eye to that of Pseudowintera colorata (Raoul) Dandy, an unrelated sympatric species found in New Zealand. Unlike the foliage of A. pusilla, that of P. colorata contains a number of secondary metabolites associated with herbivore defence, including a sesquiterpene dialdehyde known as polygodial, a known potent insect antifeedant that imparts a pungent peppery taste when eaten. It has been hypothesised that this similarity evolved under browsing pressure from nine species of large extinct herbivorous birds, collectively known as moa. Whilst moa became extinct soon after the arrival of humans, the large herbivore guild has been effectively replaced by a range of introduced mammalian herbivores including several species of deer, though to what degree remains controversial. In chapter two, I established a robust spatially explicit morphometric analysis method to test how similar the leaves of A. pusilla and P. colorata leaves were, and whether leaf shape was a distinctive trait within their shared habitat. Using the Cartesian coordinates of leaf margins as descriptors of leaf shape, I found that P. colorata leaves were morphologically distinct from all of the neighbouring species except for those of A. pusilla. A. pusilla individuals were more similar to neighbouring than to distant P. colorata, and 90% of leaf shape variation in the two species varied similarly across an elevational gradient. The data are consistent with Batesian mimicry, wherein the conspicuous characteristic of a defended model is replicated by an undefended mimic across its entire growing range. In chapter three, I tested how leaf shape variation within, and between, A. pusilla and P. colorata responded when exposed to high levels of mammalian herbivory. I demonstrated that in a forest population of P. colorata and A. pusilla exposed to high mammalian herbivory pressure, leaf shape variation is reduced in both focal species, but not in other sympatric species. This is consistent with Batesian mimicry, wherein increased herbivory pressure selects for a stronger signal in the distinctive characteristic of the defended plant, and through the selection for mimicry, variation in the mimic’s phenotype converges on the model’s phenotype. Additionally, when alternative palatable food is preferentially targeted, P. colorata increased in abundance along with a proportionate increase in A. pusilla’s abundance. Invertebrate herbivory was estimated to be similar on both species at both sites. In chapter four, I tested the hypothesis that A. pusilla is a Batesian mimic of P. colorata using farmed red deer (Cervus elaphus scoticus) in feeding trials. The deer found A. pusilla more palatable than P. colorata, and after eating a P. colorata individual, they became reluctant to eat another plant. Although the two plants differ significantly in volatile organic compound emissions, deer were equally likely to first eat an A. pusilla as they were a P. colorata, therefore were unable to use olfactory cues, or visually differentiate between the two species. As the relative abundance of P. colorata increased, herbivory damage was lower, both in the defended P. colorata and in the undefended A. pusilla. This study provides the first unequivocal proof of defensive Batesian mimicry in plants. In chapter five, using humans as surrogate herbivores, I tested how leaf shape and colour can be used as cues or signals by herbivores when foraging for food under different conditions. Subjects found leaf size a distracting characteristic, foraging more effectively when A. pusilla and P. colorata individuals were most similar in 94% of their shared shape variation. The trait of leaf colour, whilst unreliable by itself, acted to potentiate the trait of leaf shape, as a signal or cue. Fast feedback on species palatability improved accuracy in identifying A. pusilla, but neither fast nor slow feedback improved discriminability of P. colorata. A. pusilla leaves were harder to discriminate when presented on a “disruptive” backdrop. My results demonstrate that leaf shape can act as a signal or cue. These results indicate why further research into plant-herbivore communication is important and that it could provide powerful insights into the functional significance of leaf morphology. This thesis provides a significant contribution to our understanding of how leaves function as signals or cues to herbivores in three ways: (i) it provides the first detailed and powerful quantitative evidence of leaf shape matching between two species, and demonstrates the importance of using a spatially explicit morphometric method when investigating leaf shape; (ii) it is the first to unequivocally prove defensive Batesian mimicry in plants; and (iii) it demonstrates that leaf traits can act as signals or cues.</p>

Batesian mimicry in plants: The significance of shared leaf shape between Alseuosmia pusilla and Pseudowintera colorata

<p>There is an immense amount of variation in leaf shape, size, and colouration, both across and within plant species. Leaf shape and colour, in some instances, can be attributed as a physiological response to particular abiotic stressors. However, leaf shape, size, and colour are used by herbivores to identify sources of palatable foliage for food. It is possible, therefore, that an undefended plant might gain protection from herbivores by matching leaf characteristics of a chemically defended species. The matching of defensive signals by an undefended species in order to dupe a predator is known as Batesian mimicry, and whilst believed to be a relatively common phenomenon amongst animals, it has yet to be proven in plants. The foliage of Alseuosmia pusilla (Colenso) A. Cunningham, is strikingly similar to the human eye to that of Pseudowintera colorata (Raoul) Dandy, an unrelated sympatric species found in New Zealand. Unlike the foliage of A. pusilla, that of P. colorata contains a number of secondary metabolites associated with herbivore defence, including a sesquiterpene dialdehyde known as polygodial, a known potent insect antifeedant that imparts a pungent peppery taste when eaten. It has been hypothesised that this similarity evolved under browsing pressure from nine species of large extinct herbivorous birds, collectively known as moa. Whilst moa became extinct soon after the arrival of humans, the large herbivore guild has been effectively replaced by a range of introduced mammalian herbivores including several species of deer, though to what degree remains controversial. In chapter two, I established a robust spatially explicit morphometric analysis method to test how similar the leaves of A. pusilla and P. colorata leaves were, and whether leaf shape was a distinctive trait within their shared habitat. Using the Cartesian coordinates of leaf margins as descriptors of leaf shape, I found that P. colorata leaves were morphologically distinct from all of the neighbouring species except for those of A. pusilla. A. pusilla individuals were more similar to neighbouring than to distant P. colorata, and 90% of leaf shape variation in the two species varied similarly across an elevational gradient. The data are consistent with Batesian mimicry, wherein the conspicuous characteristic of a defended model is replicated by an undefended mimic across its entire growing range. In chapter three, I tested how leaf shape variation within, and between, A. pusilla and P. colorata responded when exposed to high levels of mammalian herbivory. I demonstrated that in a forest population of P. colorata and A. pusilla exposed to high mammalian herbivory pressure, leaf shape variation is reduced in both focal species, but not in other sympatric species. This is consistent with Batesian mimicry, wherein increased herbivory pressure selects for a stronger signal in the distinctive characteristic of the defended plant, and through the selection for mimicry, variation in the mimic’s phenotype converges on the model’s phenotype. Additionally, when alternative palatable food is preferentially targeted, P. colorata increased in abundance along with a proportionate increase in A. pusilla’s abundance. Invertebrate herbivory was estimated to be similar on both species at both sites. In chapter four, I tested the hypothesis that A. pusilla is a Batesian mimic of P. colorata using farmed red deer (Cervus elaphus scoticus) in feeding trials. The deer found A. pusilla more palatable than P. colorata, and after eating a P. colorata individual, they became reluctant to eat another plant. Although the two plants differ significantly in volatile organic compound emissions, deer were equally likely to first eat an A. pusilla as they were a P. colorata, therefore were unable to use olfactory cues, or visually differentiate between the two species. As the relative abundance of P. colorata increased, herbivory damage was lower, both in the defended P. colorata and in the undefended A. pusilla. This study provides the first unequivocal proof of defensive Batesian mimicry in plants. In chapter five, using humans as surrogate herbivores, I tested how leaf shape and colour can be used as cues or signals by herbivores when foraging for food under different conditions. Subjects found leaf size a distracting characteristic, foraging more effectively when A. pusilla and P. colorata individuals were most similar in 94% of their shared shape variation. The trait of leaf colour, whilst unreliable by itself, acted to potentiate the trait of leaf shape, as a signal or cue. Fast feedback on species palatability improved accuracy in identifying A. pusilla, but neither fast nor slow feedback improved discriminability of P. colorata. A. pusilla leaves were harder to discriminate when presented on a “disruptive” backdrop. My results demonstrate that leaf shape can act as a signal or cue. These results indicate why further research into plant-herbivore communication is important and that it could provide powerful insights into the functional significance of leaf morphology. This thesis provides a significant contribution to our understanding of how leaves function as signals or cues to herbivores in three ways: (i) it provides the first detailed and powerful quantitative evidence of leaf shape matching between two species, and demonstrates the importance of using a spatially explicit morphometric method when investigating leaf shape; (ii) it is the first to unequivocally prove defensive Batesian mimicry in plants; and (iii) it demonstrates that leaf traits can act as signals or cues.</p>

Global distribution of mammal herbivore biomass reveals megafauna extinction patterns

Terrestrial mammalian herbivores strongly shape ecosystems and influence Earth system processes. Herbivorous mammals can alter vegetation structure, accelerate nutrient distribution, and modify carbon cycling. The Late Pleistocene megafauna extinctions triggered significant changes in ecosystems and climate, and current extinctions are having similarly pervasive consequences. A lack of global dynamic models of mammal populations limits our understanding of the ecological role of wild mammals and the consequences of their past and future extinctions. Here we present a global model of herbivore mammal populations defined by their ecological role based on a classification of all extant herbivores (n = 2599) in 24 functional groups. The eco-physiological model predicts present-day mammal biomass in natural conditions. Biomass hotspots occur in areas today dominated by humans, which account for 30% of biomass loss and limit future rewilding potentials. Large herbivore (body mass > 5 kg) biomass is higher in hot and wet areas with high evapotranspiration. Conversely, small herbivore biomass is more evenly distributed, particularly in colder climates. Thus, energy-water dependency is higher in large herbivores than smaller ones. Negative deviations from the biomass and water-energy relationship unveil past extinction patterns. Late Pleistocene extinctions may have triggered a collapse of biomass in Australia and South America and heavy losses in North America and northern Asia. The herbivore biomass estimates provide a quantitative benchmark for conservation and management actions. The herbivore model and the functional classification create new opportunities to integrate mammals into Earth system science.

Does timing of birth affect juvenile and mare survival in wild plains zebra?

In large herbivores, the timing of births is mainly driven by the seasonal availability of their food resource. Population dynamics is strongly influenced by juvenile survival and recruitment, which highly depend on whether individuals are born during a favourable period or not. If births often occur during the most suitable season in northern cyclical environments for many large herbivore species, zebra give birth year-round at Hwange National Park, Zimbabwe, a tropical bushland characterized by the succession of a favourable wet season and a less favourable dry season. We used capture-recapture models for analysing long term observation data collected between 2008 and 2019 in this zebra population. We investigated the effect of the season (as a categorical variable) and the time spent in dry season on three categories of juveniles (younger foals of less than six months old, older foals between six and twelve months old, and yearlings between one and two years old) and mares survival, according to their reproductive state. The season had no effect on any survival. Younger foals annual survival was not affected by the time spent in dry season, whereas older foals and yearlings annual survival decreased with an increasing exposure to the dry season. Mares annual survival also decreased with an increasing time spent in dry season, whatever the reproductive status, but to a large extend when non-reproducing. The timing of birth, by determining the external conditions experienced by the offspring and their mothers during critical phases of their life cycle, plays a determinant role in their survival. As climate change is expected to lead to more frequent droughts, longer and harsher dry seasons in tropical ecosystems, we hypothesize a detrimental effect on zebra population dynamics in the future.

Large herbivores suppress liana infestation in an African savanna

African savannas are the last stronghold of diverse large-mammal communities, and a major focus of savanna ecology is to understand how these animals affect the relative abundance of trees and grasses. However, savannas support diverse plant life-forms, and human-induced changes in large-herbivore assemblages—declining wildlife populations and their displacement by livestock—may cause unexpected shifts in plant community composition. We investigated how herbivory affects the prevalence of lianas (woody vines) and their impact on trees in an East African savanna. Although scarce (<2% of tree canopy area) and defended by toxic latex, the dominant liana, Cynanchum viminale (Apocynaceae), was eaten by 15 wild large-herbivore species and was consumed in bulk by native browsers during experimental cafeteria trials. In contrast, domesticated ungulates rarely ate lianas. When we experimentally excluded all large herbivores for periods of 8 to 17 y (simulating extirpation), liana abundance increased dramatically, with up to 75% of trees infested. Piecewise exclusion of different-sized herbivores revealed functional complementarity among size classes in suppressing lianas. Liana infestation reduced tree growth and reproduction, but herbivores quickly cleared lianas from trees after the removal of 18-y-old exclosure fences (simulating rewilding). A simple model of liana contagion showed that, without herbivores, the long-term equilibrium could be either endemic (liana–tree coexistence) or an all-liana alternative stable state. We conclude that ongoing declines of wild large-herbivore populations will disrupt the structure and functioning of many African savannas in ways that have received little attention and that may not be mitigated by replacing wildlife with livestock.

Drone Surveys Revealed Bottom-Up, And Not Top-Down, Effects On The Marsh Deer Local Abundance

Context: Spatial variation in large herbivore populations can be highly affected by the availability of resources (bottom-up) but modulated by the presence of predators (top-down). Studying the relative influence of these forces has been a major topic of interest in ecological and conservation research, while it has also been challenging to sample large herbivores. Objective: i) Explore the use of spatiotemporally replicated drone-based counts analysed with N-mixture models to estimate abundance of large herbivores. ii) Evaluate the relative influence of bottom-up (forage and water) and top-down (jaguars) processes on the local abundance of the threatened marsh deer.Methods: We conducted spatiotemporally replicated drone flights in the dry season of Pantanal wetland (Brazil) and imagery was reviewed by either one or two observers. We fitted counts using N-mixture models (for single and double observer protocols) and modelled local abundance in relation to vegetation greenness, distance to water bodies, and jaguar density.Results: We found a positive relationship of marsh deer local abundance with vegetation greenness, a negative relationship with distance to water, but no relation with jaguar density. Individuals were concentrated in the lower and wetter region, even though it is the area expected to be more lethal from jaguar predation.Conclusions: Bottom-up processes are shaping the distribution of marsh deer in the dry season; the benefits of accessing high-quality areas outweigh predation risk from jaguars. Spatiotemporally replicated drone-based counts may serve as an accessible and cost-effective protocol for large herbivores abundance estimation and monitoring while accounting for imperfect detection.