摘要: Spatiotemporal interactions between predators and prey are central to maintaining sustainable functioning ecosystems and community stability. For wild ungulates and their predators, livestock grazing is an important anthropogenic disturbance causing population declines and modifying their interactions over time and space. However, it is poorly understood how fine-scale grazing affects the spatiotemporal responses of predators, prey, and their interactions. Two opposing hypotheses describe a dichotomy of possible effects. The human shield hypothesis states that people can protect prey because predators avoid areas with high human-induced mortality risk, whereas in the human competitor hypothesis, humans compete for prey and negatively impact predators through reduced prey availability. We used camera-trapping data from the Gansu Qilianshan National Nature Reserve in Northwest China to measure occupancy, daily activity patterns, and spatiotemporal interactions between snow leopards (Panthera uncia), the dominant predator, and their ungulate prey in areas with contrasting grazing intensities. The results of grazing were consistent with both the human-shield and human-competitor hypotheses, affecting spatiotemporal patterns and interactions of predators and prey. For the primary prey species, blue sheep (Pseudois nayaur), their spatial and temporal patterns were affected by grazing, which led to a reduction in interaction frequencies with snow leopards. For secondary prey, grazing led to reduced interaction frequencies with snow leopards for white-lipped deer (Przewalskium albirostris) and red deer (Cervus yarkandensis), but increased frequencies for alpine musk deer (Moschus chrysogaster). Our results indicate how both competition among livestock and prey and predator or prey avoidance of grazed areas can impact populations and predator-prey interactions. Our findings are relevant to grazing management and snow leopard conservation.

摘要: Desmans belong to the subfamily Desmaninae, which are members of the family Talpidae. Desmans and moles show limited sexual dimorphism, making unclear sex discrimination by phenotypic assessment. The Iberian desman (Galemys pyrenaicus) is an endangered species with a severe population decline. Knowledge of sex and sex ratio is essential for conservation and management. Based on these arguments and although previous conventional PCR studies amplifying DBX/DBY genes were relatively successful in sexing the desman, high-resolution sex-specific PCR has been requested. All these reasons encouraged us to develop new species-specific RT-qPCR assays by TaqMan probes to determine the sex in desman, especially with genetic material from non-invasive samples. Accordingly, efficiency, limit of detection (LOD), specificity, and DNA analysis from faeces were verified. The target genes DBX and DBY were amplified with gDNA from both sexes, with Y-chromosome consistently absent in the female. Despite the modest efficiency, regression analysis (R-2 > 0.999) indicated a linear range of the DBX and DBY assays extending from 20 to 0.2 ng/mu L DNA. LOD analyses estimated that twice as much gDNA was needed in males as in females for DBX detection. Paradoxically, the Y-chromosome required three times as much gDNA as the X-chromosome using a male sample. Therefore, an unexpected dosage imbalance in the genome in favour of the X chromosome was discussed in light of an apparent multicopy nature of the DBX gene and with a sexing success rate of 49.9% of the non-invasive samples, supporting Fisher's principle for the mammalian XX/XY sex system, as expected.

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摘要: A species' vulnerability to extinction is influenced by both extrinsic threats (e.g., habitat loss and invasive species) and intrinsic biological traits (such as life-history traits, reproductive mode, and reproductive output). In this study, we investigated the roles of intrinsic biological traits in determining the risk of extinction across 960 oviparous species of non-avian reptiles. Our findings revealed that vulnerability to extinction is negatively correlated with clutch size, but positively correlated with egg size when controlling for body size. Surprisingly, we found that body size alone is not a predictor of extinction risk. Additionally, we observed a nonsignificant relationship between the activity phase and vulnerability to extinction across oviparous species. These results suggest that the increased risk of endangerment in oviparous reptiles may stem from declining population density due to decreasing clutch size and increasing egg mass.

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摘要: The largemouth bronze gudgeon (Coreius guichenoti), an endemic fish species, is distributed in the upper Yangtze River drainage. Due to anthropogenetic factors such as water pollution, overfishing, and dam construction, the wild populations of C. guichenoti have dramatically declined in recent decades. In this study, we generated a reference chromosomal-level genome assembly of C. guichenoti on the basis of PacBio HiFi sequencing and Hi-C scaffolding technologies. The final genome assembly was 1.10 Gb in length (contig N50: 28.64 Mb; scaffold N50: 42.39 Mb) with 25 chromosomes. The completeness score of the C. guichenoti genome was 96.4%, and high synteny was detected compared with Danio rerio and Ictalurus punctatus genomes. A total of 24 325 PCGs were annotated for the C. guichenoti genome. Comparative genomics analysis identified 986 expanded gene families in C. guichenoti, which were significantly enriched in GO items associated with the development and interaction of sperm and egg as well as immunity. Furthermore, positively selected genes (PSGs) detected in C. guichenoti were mainly associated with DNA repair, ATP binding, mitochondrion, and lipid homeostasis. Based on the reference genome and resequencing data, the polymorphic microsatellite (SSR) loci were comprehensively analyzed for C. guichenoti, and the top 15 tetra-nucleotide SSR loci were selected for the construction of the genetic maker system after validation through PCR and genotyping. All of these 15 tetra-nucleotide SSR loci without Hardy-Weinberg equilibrium (HWE) deviation showed high polymorphism, good amplification stability, and selective neutrality. The PID (sibs) curves revealed that the subset of four tetra-nucleotide SSR loci (cgui1, cgui5, cgui3, cgui13) was sufficient for accurate identification of C. guichenoti individuals (PIDsib < 0.01). These 15 tetra-nucleotide SSR loci could also serve as genetic markers in subsequent parentage identification and genetic diversity analysis. The chromosome-level genome assembly and findings laid solid foundations for molecular breeding, genomic research, and biological conservation of C. guichenoti.

摘要: Understanding the density-dependent immune response is an important theme in ecological and evolutionary studies. Animals may elevate their immune response with an increase in population density. There is substantial evidence supporting the density-dependent immune response in some insects, reptiles, and birds, but evidence is still lacking in wild rodents. Here, we tested the density-dependent immune response on Brandt's voles by manipulating their population change under both laboratory (with none or little parasite infection) and field conditions (with strong parasite infection). In the field experiment, we found that the parasite prevalence and infection intensity as well as the IgG levels increased with population density, suggesting evidence of density-dependent immune response. In the lab experiment, Brandt's voles in the high-density group experienced high crowding stress exhibited by a high frequency of locomotion and aggression, and they had a higher IgG level than those in the low-density group, but with no significant difference in parasite infection. Brandt's voles in the field had significantly higher parasite intensity and higher IgG levels than Brandt's voles in the lab. Sheep grazing and rainfall supplmentation increased IgG level but food supplementation had no significant effect on IgG level. Our study confirms density-dependent immune response in Brandt's voles, likely driven by increasing agressive behavior of voles and parasite transmission, and provides novel insight into density-dependent population regulation in small rodents oscillations.

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