Ochotona Curzoniae Research Articles

Influence of the Plateau Pika Mound Numbers on Soil Water Erosion Properties in Alpine Meadows of the Yellow River Source Zone, Western China

The plateau pika (Ochotona curzoniae) actively contributes to soil erosion and meadow degradation in western China’s Yellow River source zone. This study aimed to elucidate the effects of the pika mound numbers on the hydrodynamic characteristics and soil water erosion through simulated rainfall experiments. The inhibition effects of restored vegetation growth on meadow degradation and soil erosion were explored using a revegetated pika mound as a control. The results showed that at a rainfall intensity of 30 mm/h, the soil loss per unit time increased and then decreased with rainfall time and that 15–20 min of rainfall duration was the sensitive period for soil loss in different pika mound patch lands. The degradation of meadows due to the activities of plateau pika is an essential factor influencing soil erosion, and the soil erosion rate is positively correlated with both the pika mound numbers and slope. The mean flow velocity can better describe the process of the soil erosion, and its value increased with the number of pika mounds and slope. The Reynolds number ranged from 57.85 to 153.63 (Re <500), and it was preliminarily determined that all slope runoff was laminar flow. The Froude number increased linear function with pika mound numbers (p < 0.01), and both the pika mound numbers and slope were significant factors affecting it (p < 0.05). The Darcy–Weisbach resistance coefficient instead decreased with the pika mound numbers and slope, and the inhibitory effect of vegetation on soil erosion was probably limited when the mound numbers reached a certain level. According to the results of the grey correlation and Pearson correlation analysis, changes in the number of pika mounds led to variability in the soil water erosion properties by altering the landscape scale effect. The number of pika mound patches (NP), edge length index (TE), area index (AREA), and volume index (V) were the key influencing factors on the soil erosion rate and hydrodynamic parameters. We conclude that plateau pika activities intensify meadow degradation, and the continuous increase in pika mounds decreases the vegetation cover and flow resistance and increases soil erodibility. Controlling the intensity of plateau pika activities will effectively prevent soil erosion in degraded areas.

Protein availability on Qinghai–Tibetan Plateau meadows determines density and life-history characteristics of plateau pikas (Ochotona curzoniae)

Abstract Plateau pikas (Ochotona curzoniae) play a keystone role in the alpine meadow ecosystem on the Qinghai–Tibetan Plateau (QTP). For decades, alpine meadows on the QTP have suffered from severe degradation, predominantly due to livestock grazing and frequent dramatic increases in plateau pikas. The cause has long been thought to be that livestock grazing provides open habitats for pikas. However, open habitats with low food nutrient quality are insufficient to maintain high-density populations. Feeding facilitation is a process or action undertaken by one species whose activity benefits another species. However, the facilitative effects on population consequences remain unclear. Here, we examined the impact of feeding facilitation on the population dynamics of plateau pikas. We hypothesize that the high protein amount provided by meadows that have been overgrazed would be an important factor leading to dramatic increases in plateau pikas. We found that plateau pikas preferred high-protein foods, and relatively abundant high-protein food resources were found in meadows following high levels of livestock grazing. Body mass and amount of protein in stomach digesta of pikas were higher in moderately and heavily grazed meadows than in lightly grazed meadow. Thus, pika population density was associated with high-protein food resources. A supplemental protein experiment confirmed that high-protein foods led to higher pika population density by increasing reproductive performance. Livestock grazing increased the abundance of plateau pikas by shifting plant nutrient contents toward higher protein conditions favorable to them. Feeding facilitation is an important factor that causes a dramatic increase in plateau pikas.

Establishment of a secondary infection laboratory model of Echinococcus shiquicus metacestode using BALB/c mice and Mongolian jirds (Meriones unguiculatus).

Echinococcus shiquicus is peculiar to the Qinghai–Tibet plateau of China. Research on this parasite has mainly focused on epidemiological surveys and life cycle studies. So far, limited laboratory studies have been reported. Here, experimental infection of E. shiquicus metacestode in BALB/c mice and Mongolian jirds (Meriones unguiculatus) was carried out to establish alternative laboratory animal models. Intraperitoneal inoculation of metacestode material containing protoscoleces (PSCs) obtained from infected plateau pikas were conducted on BALB/c mice. Furthermore, metacestode material without PSCs deriving from infected BALB/c mice was intraperitoneally inoculated to Mongolian jirds. Experimental animals were dissected for macroscopic and histopathological examination. The growth of cysts in BALB/c mice was infiltrative, and they invaded the murine entire body. Most of the metacestode cysts were multicystic, but a few were unilocular. The cysts contained sterile vesicles, which had no PSCs. The metacestode materials were able to successfully infect new mice. In the jirds model, E. shiquicus cysts were typically formed freely in the peritoneal cavity; the majority of these cysts were free while a small portion adhered loosely to nearby organs. The proportion of fertile cysts was high, and contained many PSCs. The PSCs produced in Mongolian jirds also successfully infected new ones, which confirms that jirds can serve as an alternative experimental intermediate host. In conclusion, a laboratory animal infection was successfully established for E. shiquicus using BALB/c mice and Mongolian jirds. These results provide new models for the in-depth study of Echinococcus metacestode survival strategy, host interactions and immune escape mechanism.

Analyzing the recovery mechanisms of patchy degradation and its response to mowing and plateau pika disturbances in alpine meadow

The alpine meadow is susceptible to degradation triggered by overgrazing and rodent outbreaks, leading to uneven patches of degradation. In this regard, we conducted a study that involved the implementation of nine combined treatments utilizing a two-factor randomized block design. The treatments were established based on three levels of plateau pika densities and three levels of simulated grazing intensity (mowing), and were replicated three times, resulting in 27 test plots. Hyperspectral images were used to map healthy meadow (HM), long-term vegetated patch (LVP), and short-term vegetated patch (SVP) and characterize their spectral properties. Four vegetation indices, including modified red edge simple ratio (MRESR), photochemical reflectance index (PRI), anthocyanin reflectance index (ARI), and plant senescence reflectance index (PSRI), were used to measure the recovery rate of various patches. In order to measure the resilience of various patches, the ratio of the LVP to degraded patch coverage (RLDC) and ratio of the SVP to degraded patch coverage (RSDC) were calculated from nadir-viewing drone images of the test plots. The research findings indicate that moderate mowing negatively affects the vegetative recovery rate of grass in healthy meadow. A moderate density of plateau pika facilitates plant growth in various types of patches. The joint action of plateau pika and mowing amplifies the negative effects of both factors while neutralizing their positive effects. SVP plants improve community resilience by shortening their life cycle and sprouting in cracks of soil crust. SVPs exhibit high resilience and can withstand local severe interference by plateau pika and grazing activities. LVPs require a stable environment for healthy meadow and cannot adapt to the disturbance of plateau pika at any density. Under the joint interferences of plateau pika and mowing, the SVPs could not be replaced by the LVPs. Therefore, the restoration and management of patchily degraded meadow must consider enhancing the resilience of plant patches and maintaining the long-term and stable survival of the restored grassland.

Species-Level Taxonomic Characterization of Uncultured Core Gut Microbiota of Plateau Pika.

Rarely has the vast diversity of bacteria on Earth been profiled, particularly on inaccessible plateaus. These uncultured microbes, which are also known as "microbial dark matter," may play crucial roles in maintaining the ecosystem and are linked to human health, regarding pathogenicity and prebioticity. The plateau pika (Ochotona curzoniae) is a small burrowing steppe lagomorph that is endemic to the Qinghai-Tibetan Plateau and is a keystone species in the maintenance of ecological balance. We used a combination of full-length 16S rRNA amplicon sequencing, shotgun metagenomics, and metabolomics to elucidate the species-level community structure and the metabolic potential of the gut microbiota of the plateau pika. Using a full-length 16S rRNA metataxonomic approach, we clustered 618 (166 ± 35 per sample) operational phylogenetic units (OPUs) from 105 plateau pika samples and assigned them to 215 known species, 226 potentially new species, and 177 higher hierarchical taxa. Notably, 39 abundant OPUs (over 60% total relative abundance) are found in over 90% of the samples, thereby representing a "core microbiota." They are all classified as novel microbial lineages, from the class to the species level. Using metagenomic reads, we independently assembled and binned 109 high-quality, species-level genome bins (SGBs). Then, a precise taxonomic assignment was performed to clarify the phylogenetic consistency of the SGBs and the 16S rRNA amplicons. Thus, the majority of the core microbes possess their genomes. SGBs belonging to the genus Treponema, the families Muribaculaceae, Lachnospiraceae, and Oscillospiraceae, and the order Eubacteriales are abundant in the metagenomic samples. In addition, multiple CAZymes are detected in these SGBs, indicating their efficient utilization of plant biomass. As the most widely connected metabolite with the core microbiota, tryptophan may relate to host environmental adaptation. Our investigation allows for a greater comprehension of the composition and functional capacity of the gut microbiota of the plateau pika. IMPORTANCE The great majority of microbial species remain uncultured, severely limiting their taxonomic characterization and biological understanding. The plateau pika (Ochotona curzoniae) is a small burrowing steppe lagomorph that is endemic to the Qinghai-Tibetan Plateau and is considered to be the keystone species in the maintenance of ecological stability. We comprehensively investigated the gut microbiota of the plateau pika via a multiomics endeavor. Combining full-length 16S rRNA metataxonomics, shotgun metagenomics, and metabolomics, we elucidated the species-level taxonomic assignment of the core uncultured intestinal microbiota of the plateau pika and revealed their correlation to host nutritional metabolism and adaptation. Our findings provide insights into the microbial diversity and biological significance of alpine animals.

Alpine grassland degradation intensifies the burrowing behavior of small mammals: evidence for a negative feedback loop.

Globally, grassland degradation is an acute ecological problem. In alpine grassland on the Tibetan Plateau, increased densities of various small mammals in degraded grassland are assumed to intensify the degradation process and these mammals are subject to lethal control. However, whether the negative impact of small mammals is solely a result of population size or also a result of activity and behavior has not been tested. In this study, we use plateau pika as a model to compare population size, core area of colony, and the number of burrow entrances and latrines between lightly and severely degraded grassland. We test whether the alleged contribution of pika to grassland degradation is a result of increased population size or increased burrowing activities of individuals in response to lower food abundance. We found that grassland degradation resulted in lower plant species richness, plant height, and biomass. Furthermore, the overall population size of pika was not significantly affected by location in lightly and severely degraded grassland. However, pika core areas in severely grassland degradation were significantly larger and had significantly higher densities of burrows and latrines. Our study provides convincing evidence that habitat-induced changes in the behavior of small, burrowing mammals, such as pika, can exacerbate grassland degradation. This finding has significant implications for managing small mammals and restoring degraded grassland ecosystems.

Daily and Seasonal Activity Patterns of Plateau Pikas (Ochotona curzoniae) on the Qinghai-Tibet Plateau, China, and Their Relationship with Weather Condition.

Exploring the activity patterns of small mammals is important for understanding the survival strategies of these animals, such as foraging and mating. The purpose of the present study was to determine the activity of free-living plateau pikas (Ochotona curzoniae) in different months and seasons (cold and warm seasons), with a particular emphasis on the effects of weather condition. Based on a camera-trapping survey conducted from October 2017 to September 2018, we evaluated the activity patterns and activity levels of plateau pikas inhabiting the eastern Qinghai-Tibet Plateau in China. The effects of environmental factors on the activity of plateau pikas were examined using the generalized additive mixed model (GAMM). The results showed that: (1) The plateau pikas exhibited unimodal patterns of activity during the cold season (October-April). During the warm season (May-September), the activity patterns of the plateau pikas were bimodal. Their activity levels were highest in June. (2) During the cold season, their activity levels rose gradually over the course of the day to a peak near noon, and they were not significantly higher after sunrise than they were before sunset. During the warm season, their activity peaks were in the morning and afternoon, and their activity levels were substantially lower after sunrise than they were before sunset. (3) The plateau pikas were more active under conditions with lower ambient temperatures and precipitation during the cold and warm seasons. While relative air humidity was positively correlated with the activity of the plateau pikas during the warm season, wind speed was negatively correlated with the pikas' activity during the cold season. Overall, these results collectively indicate that plateau pikas occupy habitats with cool and less windy microclimates during the cold season, and with cool and moist microclimates during the warm season. Information on the time allocation of pikas' activity levels during different seasons should provide a baseline for understanding their potential for adaptation to climate change.

Featured Front Cover

The cover image is based on the Research Article Vegetation restoration measures: Increasing plant height suppresses population densities of plateau pikas by Wanrong Wei et al., https://doi.org/10.1002/ldr.4600.

Altitude-dependent metabolite biomarkers reveal the mechanism of plateau pika adaptation to high altitudes.

The harsh environment in the Tibetan plateau, the highest place in the world, poses thermoregulatory challenges and hypoxic stress to animals. The impacts of plateau environment on animal physiology and reproduction include external factors such as strong ultraviolet radiation and low temperature, and internal factors such as animal metabolites and gut microbiota. However, it remains unclear how plateau pika adapt to high altitudes through the combination of serum metabolites and gut microbiota. To this end, we captured 24 wild plateau pikas at the altitudes of 3400, 3600, or 3800 m a.s.l. in a Tibetan alpine grassland. Using the machine learning algorithms (random forest), we identified five biomarkers of serum metabolites indicative of the altitudes, that is, dihydrotestosterone, homo-l-arginine, alpha-ketoglutaric-acid, serotonin, and threonine, which were related to body weight, reproduction, and energy metabolism of pika. Those metabolic biomarkers were positively correlated with Lachnospiraceae_ Agathobacter, Ruminococcaceae, or Prevotellaceae_Prevotella, suggesting the close relationship between metabolites and gut microbiota. By identifying the metabolic biomarkers and gut microbiota analysis, we reveal the mechanisms of adaptation to high altitudes in plateau pika.

Alarm Calling in Plateau Pika (Ochotona curzoniae): Evidence from Field Observations and Simulated Predator and Playback Experiments

Acoustic communication plays a vital role in passing or sharing information between individuals. Identifying the biological meaning of vocal signals is crucial in understanding the survival strategies of animals. However, there are many challenges in identifying the true meaning of such signals. The plateau pika (Ochotona curzoniae) is a call-producing mammal endemic to the Qinghai-Tibet plateau (QTP) and considered a keystone species owing to its multiple benefits in alpine rangeland ecosystems. Previous studies have shown that plateau pikas emit alarm calls as part of their daily activities. However, only field observations have been used to identify these alarm calls of the plateau pika, with no attempts at using playback experiments. Here, we report the alarm calling of plateau pikas through field observations as well as simulated predator and playback experiments in the Eastern QTP from 2021 to 2022. We found that both female and male adults emitted alarm calls, the signals of which comprised only one syllable, with a duration of 0.1-0.3 s. There were no differences in the characteristics between the observed alarm calls and those made in response to the simulated predator. The duration of the alarm call response varied with altitude, with plateau pikas living at higher altitudes responding at shorter durations than those at lower altitudes.

Emergence of an ancient and pathogenic mammarenavirus

ABSTRACT Emerging zoonoses of wildlife origin caused by previously unknown agents are one of the most important challenges for human health. The Qinghai-Tibet Plateau represents a unique ecological niche with diverse wildlife that harbours several human pathogens and numerous previously uncharacterized pathogens. In this study, we identified and characterized a novel arenavirus (namely, plateau pika virus, PPV) from plateau pikas (Ochotona curzoniae) on the Qinghai-Tibet Plateau by virome analysis. Isolated PPV strains could replicate in several mammalian cells. We further investigated PPV pathogenesis using animal models. PPV administered via an intraventricular route caused trembling and sudden death in IFNαβR-/- mice, and pathological inflammatory lesions in brain tissue were observed. According to a retrospective serological survey in the geographical region where PPV was isolated, PPV-specific IgG antibodies were detected in 8 (2.4%) of 335 outpatients with available sera. Phylogenetic analyses revealed that this virus was clearly separated from previously reported New and Old World mammarenaviruses. Under the co-speciation framework, the estimated divergence time of PPV was 77–88 million years ago (MYA), earlier than that of OW and NW mammarenaviruses (26-34 MYA).

Mammalian carcass decay increases carbon storage and temporal turnover of carbon-fixing microbes in alpine meadow soil

Corpse decomposition is of great significance to the carbon cycle of natural ecosystem. Carbon fixation is a carbon conversion process that converts carbon dioxide into organic carbon, which greatly contributes to carbon emission reduction. However, the effects of wild animal carcass decay on carbon-fixing microbes in grassland soil environment are still unknown. In this research, thirty wild mammal (Ochotona curzoniae) corpses were placed on alpine meadow soil to study the carbon storage and carbon-fixing microbiota succession for a 94-day decomposition using next-generation sequencing. Our results revealed that 1) the concentration of total carbon increased approximately 2.24–11.22% in the corpse group. 2) Several carbon-fixing bacterial species (Calothrix parietina, Ancylobacter rudongensis, Rhodopseudomonas palustris) may predict the concentration of total carbon. 3) Animal cadaver degradation caused the differentiation of carbon-fixing microbiota structures during succession and made the medium-stage networks of carbon-fixing microbes more complicated. 4) The temporal turnover rate in the experimental groups was higher than that in the control groups, indicating a quick change of gravesoil carbon-fixing microbiota. 5) The deterministic process dominates the assembly mechanism of experimental groups (ranging from 53.42% to 94.94%), which reflects that the carbon-fixing microbial community in gravesoil can be regulated. Under global climate change, this study provides a new perspective for understanding the effects of wild animal carcass decay on soil carbon storage and carbon-fixing microbes.

Group-living decrease predation risk of individual: Evidence from behavior, hormones and reproduction of plateau pika

Extensive research confirms that abiotic stressors like predation risk can profoundly affect animal condition. However, there is a lack of experimental research assessing the suite of physiological responses to risk. We increased predation risk in free-living plateau pikas (Ochotona curzoniae) by simulating natural chases using a model predator (UAV: unmanned aerial vehicle) and monitored behavior, physiology, and reproduction of pikas. We found that: Predation risk affects the body weight of plateau pika under different population density stress, but the effect is not significant. Compared with the non-predation risk treatment (control), the plateau pika under high population density stress mainly responded to the risk of predation by reducing the foraging time and increasing the vigilance time, while plateau pikas under low population density pressure not only reduce foraging time and appropriately increase vigilance time, but also focus on increasing the concealing time in the burrows. The corticosterone (CORT), cortisol and thyroid (T4) level of plateau pika with low population density under the predation risk was significantly higher than those in the control, and the testosterone (T), progesterone (PROG), leptin (LEP) and testicular weight of plateau pika with low population density in the predation risk was significantly lower than those in the control. There was no difference in the litter size of female pika between predation risk treatments and control. Broadly, our result show that predation risk had significant effects on the behavior, physiology and reproduction of plateau pikas with low population density, but had no significant effect with high population density, and the response of male plateau pika to predation risk was greater than that of female. Therefore, the prevention of plateau pika should focus on the control of population density and the protection of predators, so as to avoid the failure of ecological prevention methods such as natural enemies due to the increase of population density.

Phylogeography of the Plateau Pika (Ochotona curzoniae) in Response to the Uplift of the Qinghai-Tibet Plateau

The evolution and current distribution of species on the Qinghai-Tibet Plateau have been significantly impacted by historical occurrences, including the uplift of the plateau and the Quaternary climate upheaval. As a remnant species, the plateau pika (Ochotona curzoniae) is a great model for researching historical events. In this study, 302 samples from 42 sample sites were utilized to analyze the impact of historical events on the evolution and distribution pattern of plateau pikas. The genetic diversity, patterns of differentiation, and historical dynamics of the plateau pika were investigated using molecular markers that included four mitochondrial genes (COI, D-loop, Cytb, and 12S rRNA) and three nuclear genes (GHR, IRBP, and RAG1). The results showed that: (1) The genetic diversity of the plateau pika was high in the Tibetan Plateau (Hd = 0.9997, π = 0.01205), and the plateau pika evolved into five lineages that occupied different geographical areas, with lineage 1 (Group 1) in the south of the Yarlung Zangbo River, lineage 2 (Group 2) in the hinterland of the plateau, lineage 3 (Group 3) in the northeastern part of the plateau, lineage 4 (Group 4) in the Hengduan Mountains, and lineage 5 (Group 5) in the eastern part of the plateau. (2) The gene flow among the five lineages was low, and the differentiation level was high (Nm < 0.25; Fst > 0.25), indicating that the geographical barriers between the five lineages, such as the Yarlung Zangbo River, the Qaidam-Ghuong-Guide Basin, and the Lancang River, effectively promoted the population differentiation of the plateau pika. (3) The plateau pika first spread from the Hengduan Mountains to the entire Qinghai-Tibet Plateau and then conducted small-scale migration and dispersal in several refuges across the plateau in response to climate changes during the glacial and interglacial periods. (4) Except for Group 1 and Group 4, all the other populations exhibited a rapid expansion between 0.06 and 0.01 Mya, but the expansion was considerably delayed or halted by the effects of climate change during the last glacial maximum (0.02 Mya). Overall, the plateau pika on the Qinghai-Tibet Plateau exhibits high genetic diversity, and topographic obstacles, including mountains, valleys, and basins, created by the uplift of the plateau and climatic changes since the Quaternary period have played an important role in the differentiation and historical dynamics of the plateau pika population.

A Comparative Study on the Distribution Pattern of Endocrine Cells in the Gastrointestinal Tract of Two Small Alpine Mammals, Plateau Zokor (Eospalax baileyi) and Plateau Pika (Ochotona curzoniae)

Endocrine cells can secrete a variety of gastrointestinal hormones that regulate gastrointestinal digestion and absorption, which, in turn, play an important role in animal growth, metabolism, and acclimation. The small alpine mammals, plateau zokor (Eospalax baileyi) and plateau pika (Ochotona curzoniae), live in a unique ecotope with cold, hypoxic environments and short plant-growing seasons, resulting in differential adaptive digestive strategies for foods. Studying the distribution pattern of endocrine cells in the gastrointestinal tract (GIT) of these two animals can lead to a better understanding of the survival strategies of animals in an alpine environment. In this study, we used histochemical and immunohistochemical methods to compare the distribution pattern of argyrophilic cells and the expression of 5-HT cells, Gas cells, and Glu cells in the GIT of the plateau zokor with those of the plateau pika. The results showed that these endocrine cells we studied were widely distributed in the gastrointestinal organs of both these small mammals, and their morphology and distribution location in the GIT were almost the same. However, there were significant differences in the distribution density of argyrophilic cells between different organs in the GIT. The distribution density of argyrophilic cells in the duodenum, jejunum, ileum, and rectum of plateau zokor was significantly lower than that of plateau pika (p < 0.05) and, in the cecum of plateau zokor, was significantly higher than that of plateau pika (p < 0.001). The positive expression of 5-HT cells in the corpus I, corpus II, and pylorus of the stomach, duodenum, ileum, and rectum of plateau zokor was significantly higher than that of plateau pika (p < 0.01). In addition, the positive expression of Glu cells in the cecum was significantly higher (p < 0.01) and in the duodenum and colon was significantly lower (p < 0.05) in the plateau zokor than in the plateau pika. We conclude that the distribution pattern of endocrine cells in the GIT is consistent with the respective animals' diets, with the plateau zokor feeding on high-fiber roots and plateau pika preferring to intake the aboveground parts of plants with lower fibers.

Vegetation restoration measures: Increasing plant height suppresses population densities of plateau pikas

AbstractPlateau pikas (Ochotona curzoniae) are often regarded as pests when their population densities exceed a certain threshold. Vegetation restoration measures are commonly used for the ecological control of pikas. Nevertheless, it is not known how effective these measures are, and if effective, which factors are responsible for the decline in pika densities. Four commonly used grassland restoration measures: exclosure [E], exclosure/fertilized [EF], exclosure/overseeding [EO], exclosure/fertilization/over‐seeding [EOF], were implemented in grasslands degraded by high densities of pikas, and the pika density (PD) and vegetation traits in each treatment plot were monitored for 4 consecutive years. Neither the PD nor the vegetation composition was affected by any of the vegetation restoration measures within the first year. From the second year onwards, all the vegetation restoration measures had a significant effect on the vegetation composition and structure, such as an increase in the height, cover, and biomass. All the vegetation restoration measures, except E, had a significant suppressive effect on pika densities as time progressed, with the combination EOF measure having the largest effect. The stepwise regression analysis indicated that the vegetation height is the main factor that determines the PD. Similarly, structural equation modelling showed that vegetation restoration measures reduce PD primarily by increasing vegetation height. This may be because the height of the vegetation is closely correlated to the predation risk of pikas. Our results highlight the importance of vegetation height in pika management, suggesting that the key to successful pika management is to find a sustainable grazing system, which is beneficial to the growth of the dominant graminoids and maintains a high plant diversity for the sustainability of grassland ecosystems.

Maxent Modeling for Predicting Habitat Suitability and Potential Distribution of Plateau Pika (Ochotona curzoniae) on the Qinghai-Tibet Plateau, China

The plateau pika (Ochotona curzoniae) is a keystone species in the alpine rangeland ecosystem on the Qinghai–Tibet Plateau (QTP). However, it has been considered a pest because these mammals dig holes and make bare patches, which reduces grassland productivity. Accordingly, there is a trade-off required between biodiversity conservation and pest management. Habitat assessment is one of the critical approaches in small mammal management and protection. Although a few papers have reported the distribution of plateau pika and predicted its potential distribution under climate change at local scales in some areas, little is known about the synergistic effect of climate change and human disturbance on the wider distribution of this mammal on the QTP. In this study, we recorded 219 points of plateau pika presence on the QTP via Global Positioning System and used the Maxent model to predict potential suitable habitats. The results indicated that, under the current climate, the potential distribution of plateau pika is mainly located in southern Gansu Province, eastern Qinghai Province, and northwestern Sichuan Province, accounting for 4.44% of the total area of the QTP. The most important factors in defining habitat suitability and limiting the distribution of plateau pika include normalized difference vegetation index (29.1%), human footprint (21.6%), seasonal precipitation (11.2%), and elevation (7.8%). In the future, in the 2030s and 2050s, the total area of suitable habitat on the QTP is projected to decrease, while the habitable region in northwest Sichuan and eastern Qinghai will likely increase.

Prevalence of Echinococcus infection in small mammals captured from Shiqu County, Sichuan Province from 2015 to 2020

To investigate the prevalence of Echinococcus infection in small mammals in Shiqu County, Sichuan Province from 2015 to 2020, so as to provide insights into echinococcosis control in Shiqu County. One setting with frequent activity of small mammals was sampled as the survey site from each of 9 townships where human alveolar echinococcosis was hyperendemic, in Shiqu County, Sichuan Province from 2015 to 2020. Two quadrats measuring 50 m × 50 m were assigned in each survey site during the period between July and August from 2015 to 2020 to capture all small mammals in quadrats, and the species of small mammals were identified by morphological characteristics. All captured small mammals were dissected in the field and Echinococcus infection was identified by visual examinations. The affected organs of Echinococcus - infected small mammals were collected, and Echinococcus infection was detected using PCR assay, with Echinococcus species characterized. The prevalence of Echinococcus infection was calculated in small mammals, and the trends in the prevalence of Echinococcus infection were analyzed during the period from 2015 to 2020. In addition, the prevalence of Echinococcus infection was compared in small mammals using visual examinations and PCR assay. A total of 2 692 small mammals were captured in the survey sites of Shiqu County from 2015 to 2020, and morphology characterized 1 360 Microtus fuscus (50.52%) and 1 332 Plateau pika (49.48%). The prevalence rates of Echinococcus infection were 35.63%, 19.16%, 21.41%, 8.40%, 7.68% and 4.44% by visual examinations and 18.96%, 5.36%, 5.61%, 4.58%, 3.30% and 0.37% by PCR assay in small mammals in Shiqu County from 2015 to 2020, both showing a tendency towards a decline year by year (χ2 = 215.024 and 117.045, both P values < 0.001). The prevalence of Echinococcus infection was significantly higher in small mammals by visual examinations than by PCR assay during the period from 2015 to 2020 except in 2018 (χ2= 33.597, 21.815, 51.373, 17.268 and 9.537, all P values < 0.01). PCR assay detected a reduction in the prevalence of E. multilocularis infection from 10.21% to 0.37% and a reduction in the prevalence of E. shiquicus infection from 8.75% to 0 in small mammals in Shiqu County from 2015 to 2020, both appearing a tendency towards a decline year by year (χ2 = 117.045 and 43.436, both P values < 0.001). In addition, the prevalence of E. multilocularis and E. shiquicus infections reduced from 15.19% to 0.45% and from 8.23% to 0 in M. fuscus, and the prevalence of E. multilocularis and E. shiquicus infections reduced from 7.76% to 0 and from 9.01% to 0 in P. pika in Shiqu County from 2015 to 2020. M. fuscus and P. pika were dominant species of small mammals in Shiqu County, Sichuan Province from 2015 to 2020, and E. multilocularis infection was mainly found in M. fuscus and E. shiquicus infection mainly found in P. pika. The prevalence of Echinococcus infection appeared a tendency towards a decline in both M. fuscus and P. pika year by year during the period from 2015 to 2020.

高原鼠兔和高原鼢鼠种群暴发区干扰斑块空间分布格局与演替规律

PDF HTML阅读 XML下载 导出引用 引用提醒 高原鼠兔和高原鼢鼠种群暴发区干扰斑块空间分布格局与演替规律 DOI: 10.5846/stxb202204161021 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31872999，U21A20191）；青海省科学技术厅项目（2020-ZJ-904）；高等学校学科创新引智计划（D18013） Spatial distribution pattern and succession of disturbance patches formed by plateau pika and plateau zokor in their population outbreak areas in alpine meadow Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:高原鼠兔（Ochotona curzoniae）和高原鼢鼠（Myospalax baileyi）是两种在高寒草甸广泛分布的小型哺乳动物，其暴发活动可能造成高寒草甸的严重退化。使用无人机分别拍摄典型的高原鼠兔和高原鼢鼠种群暴发区图像，解译高原鼠兔洞口、高原鼢鼠土丘和它们的干扰斑块，获得干扰斑块的周长和面积信息，计算干扰斑块形状指标，确定高原鼠兔与高原鼢鼠暴发活动对高寒草甸的影响。研究表明：（1）高原鼠兔与高原鼢鼠暴发活动形成的干扰斑块周长与面积比（PARA）、形状指数（SHAPE）和分形维数（FRAC）差异显著（P<0.05），其中高原鼢鼠斑块的FRAC是1.0124±0.0091，属于普通的规则几何圆形分布格局，高原鼠兔斑块的FRAC是1.1203±0.0546，属于分形几何不规则的分布格局。（2）高原鼠兔洞口数量与其斑块面积没有线性相关关系（P=0.9677），高原鼢鼠土丘数量与其斑块面积呈显著正相关（P<0.05）。（3）高原鼢鼠斑块面积统计学上呈长尾分布，不符合正态分布（P<0.01）。根据高原鼠兔斑块面积分布格局可将斑块演替分为三个阶段：土丘形成阶段、斑块连通阶段和斑块扩散阶段。高原鼠兔土丘形成阶段斑块的形状和分布，与高原鼢鼠干扰斑块相似；在演替初期阶段融合连通阶段斑块的面积分布呈指数分布，形状趋于分形几何（FRAC=1.1161）；在跨尺度扩散阶段斑块面积较大且形状复杂（SHAPE=4.4202），呈现不规则分布格局。三个阶段斑块的周长与面积比、形状指数和分形维数差异显著（P<0.05）。高原鼠兔在退化高寒草甸的觅食活动促进了融合连通阶段斑块的形成，呈现分形几何斑块演替规律。由此得出结论，引起高寒草甸退化的主要原因是过度放牧下高原鼠兔暴发活动，造成跨尺度扩散斑块演替阶段出现的结果，并非高原鼢鼠的暴发活动形成的。因此，控制高原鼠兔数量并恢复高原鼠兔干扰斑块植被相比高原鼢鼠更重要。 Abstract:Plateau pika (Ochotona curzoniae) and plateau zokor (Myospalax baileyi) are two species of small mammal widely distributed in alpine meadow. The main difference between the two animals is that plateau zokor mainly lives underground and plateau pika mainly lives on the surface of grassland. Their outbreak activities may cause serious degradation of alpine meadow. The disturbance patches formed by the two animals have different effects on the alpine meadow. Which kind of animal outbreak can lead to the cross-scale succession of disturbance patches is a scientific problem that needs to be solved. The patch shape and pattern metric in the field of landscape ecology can be used to compare the patch distribution patterns, thereby understanding the differences in the formation process of various patches. In this study, Unmanned aerial vehicle (UAVs) were used to capture typical images of plateau pika and plateau zokor population outbreak areas. Plateau pika holes, plateau zokor mounds and their disturbance patches were interpreted. The perimeter and area information of the disturbance patch was obtained. The shape and pattern metrics of disturbance patch were calculated and analyzed. The effects of outbreak activities of plateau pika and plateau zokor on the degradation of alpine meadow were determined. The results indicated that (1) there were significant differences in perimeter-area ratio (PARA), shape index (SHAPE) and fractal dimension index (FRAC) between plateau pika and plateau zokor disturbance patches formed by their outbreak activities (P<0.05). The FRAC of plateau zokor patches was 1.0132±0.0103, which belongs to ordinary regular geometry (circle), and the FRAC of plateau pika patches was 1.1007±0.0576, which belongs to fractal geometry. (2) There was no correlation between the number of plateau pika holes and the patch area of plateau pika (P=0.9677). There was a significantly positive correlation between the number of mounds and the patch area of plateau zokor (P<0.05). (3) The area of plateau zokor patch showed a long tail distribution at statistics, which did not accord with the normal distribution (P<0.01). According to the patch distribution pattern of plateau pika, the succession of patches could be divided into three stages:mound stage, fusion stage and broad-scale stage. The shape and distribution pattern of patches at the mound stage were similar to those of plateau zokor patches. At the fusion stage, the patch distribution was exponential, and the shape and pattern belonged to fractal geometry (FRAC=1.1161). At the broad-scale stage, the patch pattern was large and the shape was complex (SHAPE=4.4202). The patches at the broad-scale stage were formed by the connection between the surrounding fusion stage patches and the core area of black soil degraded patches, which destroyed the dynamic balance between disturbance and restoration of alpine meadow. There were significant differences among PARA, SHAPE and FRAC at the three stages (P<0.05). The foraging activities of plateau pika in the degradation of alpine meadow promoted the formation of patches and formed fractal geometric patches at the fusion stage. The main cross-scale interaction resulting in the degradation of alpine meadow was caused by the outbreak of plateau pika, not plateau zokor. Therefore, it is more important to control the number of plateau pika and restore the disturbance patches of plateau pika than those of plateau zokor. 参考文献 相似文献 引证文献

PRNP Sequences of Tibetan Antelope, Blue Sheep, and Plateau Pika from the Qinghai-Tibet Plateau and Reactivity of PrP Proteins to Rodent-Adapted Scrapie Strains in RT-QuIC and PMCA

Background: Tibetan antelope (Rhinopithecus), blue sheep (Pseudois nayauris), and plateau pika (Ochotona curzoniae) are wild animals living on the Qinghai-Tibet Plateau. There have been no reports of naturally-occurring transmissible spongioform encephalopathies (TSEs) involving these animals. Furthermore, the PRNP genes have not been described in the literature. Methods: The PRNP genes from 21 Tibetan antelopes, 4 blue sheep, and 3 plateau pikas were obtained and sequenced. The recombinant proteins were then prepared. Using scrapie strains (263K, 139A, ME7, and S15) as the seeds, the reactivity of the PrP proteins from sheep (rSheepPrP25-234) and pika (rPikaPrP23-230) were tested using real-time quaking-induced conversion (RT-QuIC). Protein misfolding cyclic amplification (PMCA) tests of the brain homogenates from domestic sheep and rabbits were performed with the seeds of strains 263K and ME7. Results: The PRNP genes of bovids were 771 bp long and encoded 256 amino acids (aa), showing 100% homology with the wild-type sheep prion protein (PrP) aa sequence. The PRNP gene of pika was 759 bp long and encoded 252 amino acids, showing 92.1% homology with the aa sequence of domestic rabbits. The sheep and pika proteins revealed positive reactions in 10-5 diluted seeds. Only rPikaPrP23-230 produced positive curves in 10-7 diluted seeds. The PMCA tests failed to produce proteinase K (PK)-resistant PrP (PrPres). Conclusion: This is the first description of PRNP genes and PrP aa sequences of Tibetan antelope, blue sheep, and plateau pike from the Qinghai-Tibet Plateau. In the presence of rodent prions, the PrPs of sheep and pika efficiently induce fibrillation in RT-QuIC, but do not generate PrPres in PMCA. Our results indicate that pika, as one of the important links in the Qinghai-Tibet Plateau biological chain, may play an important role in the prion circulation. Pika PrP deserves further analysis for its potential application value in assays for human prion disease.