Jiapeng Qu

Pika Population Density Is Associated with the Composition and Diversity of Gut Microbiota

Host population density is positively associated with the strength of social interactions or the frequency of physical contacts, and thus potentially influences microbial transmission among individuals. However, the relationship between host density and gut microbiota remains unknown. Here, we characterized the gut microbiota of plateau pikas (Ochotona curzoniae) in wild experimental fields with different host population densities. The abundance of some gut microbes significantly correlated with host density, such as Ruminococcaceae, Lachnospiraceae, and Staphylococcaceae. Intriguingly, host density was positively correlated with alpha diversity (Shannon diversity and observed species) of gut microbial communities. The inter-individual gut microbiota within high-density groups were more similar to each other than those of low-density groups. Host density significantly explained the variations in the gut microbiota, even after controlling sex, weight, diet and geographical locations. Based on the PICRUSt metagenome prediction, positive correlations were observed between host density and the relative abundances of 12 gene functions involved in cellular processes, environmental information processing and metabolism. These results indicate the importance of host density as a factor in shaping gut microbial composition and diversity in plateau pikas, and may further help us understand the social transmission of gut microbiota.

Effects of quinestrol and levonorgestrel on populations of plateau pikas, Ochotona curzoniae, in the Qinghai-Tibetan Plateau

BACKGROUND Plateau pikas (Ochotona curzoniae, Hodgson, 1858) are viewed as a pest in the Tibetan Plateau meadow ecosystem when their population densities are high. Traditional culling using rodenticides often poses a high risk to non-target species and even to humans. In this study, an investigation was made of the infertility effects of quinestrol (E), levonorgestrel (P) and a combination of the two (EP, ratio E:P = 1:2) on plateau pikas during 2007 and 2008. RESULTS Treatment with E or EP significantly decreased the pregnancy rate of female pikas in 2007. In 2008, there was a cross-year effect that still suppressed male reproduction in treated groups. Treatment with E obviously reduced the reproduction of pikas but not their population abundance in 2007; the reduction in population size was significant in 2008. CONCLUSIONS Single baiting of quinestrol in early breeding season reduced the reproduction and population size of pikas throughout 2007. The effect of infertility lasted into the next breeding season through a cross-year effect, which resulted in a significant reduction of population size in 2008. Quinestrol is a very promising non-lethal approach to managing pika populations; however, several factors need to be investigated further to improve the practicality of this method.

Effectiveness of 10 polymorphic microsatellite markers for parentage and pedigree analysis in plateau pika (Ochotona curzoniae)

BackgroundThe plateau pika (Ochotona curzoniae) is an underground-dwelling mammal, native to the Tibetan plateau of China. A set of 10 polymorphic microsatellite loci has been developed earlier. Its reliability for parentage assignment has been tested in a plateau pika population. Two family groups with a known pedigree were used to validate the power of this set of markers.ResultsThe error in parentage assignment using a combination of these 10 loci was very low as indicated by their power of discrimination (0.803 - 0.932), power of exclusion (0.351 - 0.887), and an effectiveness of the combined probability of exclusion in parentage assignment of 99.999%.ConclusionAll the offspring of a family could be assigned to their biological mother; and their father or relatives could also be identified. This set of markers therefore provides a powerful and efficient tool for parentage assignment and other population analyses in the plateau pika.

Gut microbiota may predict host divergence time during Glires evolution

The gut microbial communities of animals play key roles in host evolution. However, the possible relationship between gut microbiota and host divergence time remains unknown. Here, we investigated the gut microbiota of eight Glires species (four lagomorph species and four rodent species) distributed throughout the Qinghai-Tibet plateau and Inner Mongolia grassland. Lagomorphs and rodents had distinct gut microbial compositions. Three out of four lagomorph species were dominated by Firmicutes, while rodents were dominated by Bacteroidetes in general. The alpha diversity values (Shannon diversity and evenness) exhibited significant differences between any two species within the lagomorphs, whereas there were no significant differences among rodents. The structure of the gut microbiota showed significant differences between lagomorphs and rodents. In addition, we calculated host phylogeny and divergence times, and used a phylogenetic approach to reconstruct how the animal gut microbiota has diverged from their ancestral species. Some core bacterial genera (e.g. Prevotella and Clostridium) shared by more than nine-tenths of all the Glires individuals associated with plant polysaccharide degradation showed marked changes within lagomorphs. Differences in Glires gut microbiota (based on weighted UniFrac and Bray-Curtis dissimilarity metrics) were positively correlated with host divergence time. Our results thus suggest the gut microbial composition is associated with host phylogeny, and further suggest that dissimilarity of animal gut microbiota may predict host divergence time.

Behavioral mechanisms of male sterilization on plateau pika in the Qinghai-Tibet plateau.

Fertility control is an alternative non-lethal method in the management of rodents. Previous modeling suggests that the efficacy of male sterilization depends on mating systems of animals, but behavioral mechanisms of male sterilization have not been investigated. Here we investigated the behavioral mechanism of the sterilant quinestrol in reducing the fertility of plateau pika (Ochotona curzoniae) inhabiting the Qinghai-Tibet plateau. Male pikas treated with quinestrol showed reduced aggression compared to control males, but they showed significantly higher levels of territorial behavior such as long-calls and long-chases. Levels of long-call and long-chase were negatively correlated with the number of newborn pikas in the family. Single-baiting of quinestrol effectively sterilized male pikas and reduced the pregnancy rate of female pikas; this was likely achieved by increased territorial behavior of sterilized pikas which resulted in unsuccessful invasions by fertile adult male pikas. Our study reveals a novel behavioral mechanism, increased territoriality in sterilized males, in the fertility control of plateau pikas.

Five-year population dynamics of plateau pikas ( Ochotona curzoniae ) on the east of Tibetan Plateau

Small mammals mediate trajectories of vegetation change where both their density and the growing season are moderated by temperature and precipitation. On the Tibetan Plateau, the cold and arid climate particularly restricts the plant growing season, but the role of mammals’ density and climate in moderating small mammal populations remains unknown. We conducted a 5-year mark-recapture study of plateau pikas (Ochotona curzoniae) to test the relative importance of density-dependent and climatic factors on survival and reproduction. Plateau pikas had seasonal fluctuations in density and survival. During the warm summer season (May–August), monthly survival was density-independent, ranging from 74.7 to 90.4%, but varied with sex and age, increased with precipitation and NDVI, and decreased with temperature. During the cold season (September–April), monthly survival was around 98%. Density and precipitation had negative effects on reproductive success for the first and second litters of the year, and temperature showed consistently positive effects on reproductive success for both litters of the year. Pika density and climate regulated together the population dynamics of plateau pikas. These data on the relationships between density and climatic factors on survival and reproduction are critical for the management and conservation of plateau pikas on the Tibetan Plateau.

Genetic diversity and sex-bias dispersal of plateau pika in Tibetan plateau

Abstract Dispersal is an important aspect in organisms life history which could influence the rate and outcome of evolution of organism. Plateau pika is the keystone species in community of grasslands in Tibetan Plateau. In this study, we combine genetic and field data to character the population genetic pattern and dispersal dynamics in plateau pika (Ochotona curzoniae). Totally, 1,352 individual samples were collected, and 10 microsatellite loci were analyzed. Results revealed that plateau pika possessed high genetic diversity and inbreeding coefficient in a fine‐scale population. Dispersal distance is short and restricted in about 20 m. An effective sex‐biased dispersal strategy is employed by plateau pika: males disperse in breeding period for mating while females do it after reproduction for offspring and resource. Inbreeding avoiding was shown as the common driving force of dispersal, together with the other two factors, environment and resource. In addition, natal dispersal is female biased. More detailed genetic analyzes are needed to confirm the role of inbreeding avoidance and resource competition as ultimate cause of dispersal patterns in plateau pika.

The more the merrier? Multi-species grazing of small herbivores mediates plant community impacts

Small herbivores play keystone functional roles in grassland ecosystems. Recognising the combined effects where herbivores co-exist is important for guiding grassland restoration and biodiversity conservation. On the Tibetan Plateau, both plateau pikas and Himalayan marmots are regarded as pests by Tibetan people and local government, but little is known about their combined effects. We conducted a field study to determine the combined effects of pikas and marmots on plant biodiversity and vegetation structure. Plateau pikas alone consistently reduced the plant height and diversity and increased the vegetation cover of physically unpalatable plants. However, the co-existence of marmots with pikas decreased the vegetation cover of physically unpalatable plants, while increasing the cover of palatable plants and plant diversity, ultimately changing the impact of pikas alone and modulating aspects of the plant community. These results illustrate that increasing the abundance and richness of small herbivores in grassland ecosystems may promote plant diversity and benefit vegetation restoration rather than aggravate the degradation of grasslands.

Independence between coping style and stress reactivity in plateau pika

The concept of coping style represents the way individual animals react to a stressful situation, both behaviourally and neurophysiologically. Over the last decades coping style has been linked to the development of research on animal personality. Based on this concept, we should find a proactive-reactive continuum in animal populations, with proactive individuals being fast explorer, bold, aggressive, and show high sympathetic reactivity (higher heart rate), as well as low hypothalamus-pituitary-adrenocortical (PHA) axis reactivity to external stressor (higher plasma glucocorticoid level). At the other extreme, shy, lowly aggressive, reactive individuals should be slow in their exploration, and show a low sympathetic reactivity and a high HPA axis reactivity. However, a recent two-tier model proposed that coping style and stress reactivity should be independent of each other. In this study, we tested the two-tier model in a wild plateau pika (Ochotona curzoniae) population on the Tibetan Plateau, by quantifying the associations between several behavioural and physiological traits at the among- and within-individual levels. We repeatedly measured exploration, docility, boldness, heart rate and plasma cortisol concentration in individuals between April and September of 2013. All traits tested were repeatable. At the among-individual level, all behavioural traits were correlated with each other and with heart rate, but were independent of both basal level and variation of plasma cortisol concentration. Most correlations were negligible at the within-individual level. In support of the two-tier model, these results suggest that coping style (i.e. behaviour and heart rate associations) is independent of stress reactivity (i.e. glucocorticoid reactivity) in that species.

Gut Microbiota in Tibetan Herdsmen Reflects the Degree of Urbanization

Urbanization is associated with shifts in human lifestyles, thus possibly influencing the diversity, interaction and assembly of gut microbiota. However, the question regarding how human gut microbiota adapts to varying lifestyles remains elusive. To understand the relationship between gut microbiota and urbanization, we compared the diversity, interaction and assembly of gut microbial communities of herdsmen from three regions with different levels of urbanization, namely traditional herdsmen (TH), semi-urban herdsmen (SUH) and urban herdsmen (UH). The relative abundance of Prevotella decreased with the degree of urbanization (from TH to UH), whereas that of Bacteroides, Faecalibacterium, and Blautia showed an opposite trend. Although the alpha diversity measures (observed OTUs and phylogenetic diversity) of gut microbiota were unaffected by urbanization, the beta diversity (Jaccard or Bray–Curtis distances) was significantly influenced by urbanization. Metagenome prediction revealed that the gene functions associated with metabolism (i.e., carbohydrate and lipid metabolism) had significant differences between TH and UH. Network analysis showed that the modularity increased with the degree of urbanization, indicating a high extent of niche differentiation in UH. Meanwhile the trend of network density was opposite, indicating a more complex network in TH. Notably, the relative importance of environmental filtering that governed the community assembly increased with the degree of urbanization, which indicated that deterministic factors (e.g., low-fiber diet) play more important roles than stochastic factors (e.g., stochastic dispersal) in shaping the gut microbiota. A quantification of ecological processes showed a stronger signal of variable selection in UH than TH, implying that different selective pressures cause divergent gut community compositions due to urban lifestyles. Our results suggest that beta diversity, network interactions and ecological processes of gut microbiota may reflect the degree of urbanization, and highlight the adaptation of human gut microbiota to lifestyle changes.