Freshwater fish biodiversity is quickly decreasing and requires effective monitoring and conservation. Environmental DNA (eDNA)‐based methods have been shown to be highly sensitive and cost‐efficient for aquatic biodiversity surveys, but few studies have systematically investigated how spatial sampling design affects eDNA‐detected fish communities across lentic systems of different sizes. We compared the spatial patterns of fish diversity determined using eDNA in three lakes of small (SL; 3 ha), medium (ML; 122 ha) and large (LL; 4,343 ha) size using a spatially explicit grid sampling method. A total of 100 water samples (including nine, 17 and 18 shoreline samples and six, 14 and 36 interior samples from SL, ML and LL, respectively) were collected, and fish communities were analysed using eDNA metabarcoding of the mitochondrial 12S region. Together, 30, 35 and 41 fish taxa were detected in samples from SL, ML, and LL, respectively. We observed that eDNA from shoreline samples effectively captured the majority of the fish diversity of entire waterbodies, and pooled samples recovered fewer species than individually processed samples. Significant spatial autocorrelations between fish communities within 250 m and 2 km of each other were detected in ML and LL, respectively. Additionally, the relative sequence abundances of many fish species exhibited spatial distribution patterns that correlated with their typical habitat occupation. Overall, our results support the validity of a shoreline sampling strategy for eDNA‐based fish community surveys in lentic systems but also suggest that a spatially comprehensive sampling design can reveal finer distribution patterns of individual species.

Large mammalian carnivores have undergone catastrophic declines during the Anthropocene across the world. Despite their pivotal roles as apex predators in food webs and ecosystem dynamics, few detailed dietary datasets of large carnivores exist, prohibiting deep understanding of their coexistence and persistence in human-dominated landscapes. Here, we present fine-scaled, quantitative trophic interactions among sympatric carnivores from three assemblages in the Mountains of Southwest China, a global biodiversity hotspot harboring the world's richest large-carnivore diversity, derived from DNA metabarcoding of 1,097 fecal samples. These assemblages comprise a large-carnivore guild ranging from zero to five species along with two mesocarnivore species. We constructed predator-prey food webs for each assemblage and identified 95 vertebrate prey taxa and 260 feeding interactions in sum. Each carnivore species consumed 6-39 prey taxa, and dietary diversity decreased with increased carnivore body mass across guilds. Dietary partitioning was more evident between large-carnivore and mesocarnivore guilds, yet different large carnivores showed divergent proportional utilization of different-sized prey correlating with their own body masses. Large carnivores particularly selected livestock in Tibetan-dominated regions, where the indigenous people show high tolerance toward wild predators. Our results suggest that dietary niche partitioning and livestock subsidies facilitate large-carnivore sympatry and persistence and have key implications for sustainable conservation promoting human-carnivore coexistence.

Biodiversity conservation relies on effective practical methods for assessing species occurrences and distributions, particularly for elusive species. Generalist carnivores are widely distributed and relatively abundant predators with broad dietary ranges, and as such could potentially serve as “biodiversity samplers” of sympatric prey communities. To test this hypothesis, we analyzed leopard cat (Prionailurus bengalensis) and red fox (Vulpes vulpes) diets to survey local vertebrate communities in several mountainous areas in China. Fecal DNA metabarcoding analysis revealed that leopard cat prey from five mountain ranges across China included 99 vertebrate taxa representing 12 taxonomic orders and red fox prey from two of those mountain ranges displayed a similar degree of diversity, which was highly correlated with local species records accrued by traditional survey methods. Our results show that diet metabarcoding analysis of generalist carnivores can be an effective, noninvasive, and economically viable tool for biodiversity monitoring to inform management decisions. In addition, we explored selection criteria and potential candidate species for carnivore sampler‐based biodiversity studies in other parts of the world.

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As the apex predator of plateau ecosystems in Central Asia and the Qinghai-Tibet Plateau, the snow leopard (Panthera uncia) plays an essential role in maintaining food-web structure and ecosystem stability. Learning the diet composition and dynamics of the snow leopard is important for understanding its role in ecosystem functioning and interspecific interactions. Previous diet analyses of the snow leopard have been based mainly on morphological identification of food debris in the feces, though the accuracy of this practice has been broadly debated. The Qionglai Mountains are located at the southeast edge of the snow leopard range, harboring a small and relatively isolated population of snow leopards that are barely studied. Using non-invasive sampling, we collected 38 putative snow leopard fecal samples in the Wolong National Nature Reserve in the Qionglai Mountains. To identify the fecal origin, we extracted the fecal DNA and amplified the mitochondrial DNA 16S rRNA gene fragment. Twenty-two fecal samples were identified as originating from snow leopards. Subsequently, vertebrate universal primers and a snow leopard-specific blocking oligo were used to amplify the food components in the fecal DNA, and then high-throughput sequencing was performed to analyze the diet composition of snow leopards. The blue sheep