The Asian elephant (Elephas maximus) population in Nangunhe National Nature Reserve in China represents a unique evolutionary branch that has been isolated for more than twenty years from neighboring populations in Myanmar. The scarcity of information on population structure, sex ratio, and body condition makes it difficult to develop effective conservation measures for this elephant population. Twelve individuals were identified from 3,860 valid elephant images obtained from February to June 2018 (5,942 sampling effort nights) at 52 camera sites. Three adult females, three adult males, one subadult male, two juvenile females, two juvenile males and one male calf were identified. The ratio of adult females to adult males was 1:1, and the ratio of reproductive ability was 1:0.67, indicating the scarcity of reproductive females as an important limiting factor to population growth. A population density of 5.32 ± 1.56 elephants/100 km² was estimated using Spatially Explicit Capture Recapture (SECR) models. The health condition of this elephant population was assessed using an 11-point scale of Body Condition Scoring (BCS). The average BCS was 5.75 (n = 12, range 2–9), with adult females scoring lower than adult males. This isolated population is extremely small and has an inverted pyramid age structure and therefore is at a high risk of extinction. We propose three plans to improve the survival of this population: improving the quality and quantity of food resources, removing fencing and establishing corridors between the east and wet parts of Nangunhe reserve.

The genomic consequences of prolonged population decline and isolation are increasingly recognized, but quantitative assessments of mutation loads have been limited by low population-level replication in individual studies. Moreover, how inbreeding and purifying selection shape the genomic landscape of deleterious variation remains poorly understood. We evaluated the abundance and frequency of putative deleterious mutations, characterized the landscape of deleterious variation, and measured the efficacy of purifying selection in 17 wild nine-spined stickleback (Pungitius pungitius) populations covering varying levels of inbreeding (FROH = 0.015 to 0.912) and histories of isolation. We found significantly more deleterious homozygous mutations and a greater frequency of mildly deleterious variants in long-term small, isolated, and inbred populations than in larger outbred populations. Deleterious homozygotes were enriched in runs of homozygosity regions across all study populations, but the extent of enrichment was more pronounced in larger outbred populations than in small inbred populations. Historical effective population sizes serve as an indicator of the strength of purifying selection for mildly deleterious alleles but not for strongly deleterious alleles. The results demonstrate that the accumulation and purging of deleterious variants can occur simultaneously and that a large fraction of segregating strongly deleterious variants are recessive lethals. These findings, which are based on analyses of highly replicated samples of populations, suggest that the level of inbreeding is a good predictor of realized loads of deleterious mutations and that the genomic consequences of prolonged isolation in small populations are predictable.

Many endangered species live in fragmented and isolated populations with low genetic variability, signs of inbreeding, and small effective population sizes - all features elevating their extinction risk. The flat-headed loach (Oreonectes platycephalus), a small noemacheilid fish, is widely across southern China, but only in the headwaters of hillstreams; as a result, they are spatially isolated from conspecific populations. We surveyed single nucleotide polymorphisms in 16 Hong Kong populations of O. platycephalus to determine whether loach populations from different streams were genetically isolated from each other, showed low levels of genetic diversity, signs of inbreeding, and had small contemporary effective population sizes. Estimates of average observed heterozygosity (H_O = 0.0473), average weighted nucleotide diversity (π_w = 0.0546) and contemporary effective population sizes (N_e = 10.2 ~ 129.8) were very low, and several populations showed clear signs of inbreeding as judged from relatedness estimates. The degree of genetic differentiation among populations was very high (average F_ST = 0.668), even over short geographic distances (<1.5 km), with clear patterns of isolation by distance. These results suggest that Hong Kong populations of O. platycephalus have experienced strong genetic drift and loss of genetic variability because sea-level rise after the last glaciation reduced connectedness among paleodrainages, isolating populations in headwaters. All this, together with the fact that the levels of genetic diversity and contemporary effective population sizes within O. platycephalus populations are lower than most other freshwater fishes, suggests that they face high local extinction risk and have limited capacity for future adaptation.

Understanding the diet composition and preferences of large herbivores not only provides insights into their ecological role, but also helps to assess the viability of elephant populations and their habitats. This study was performed to determine the diet preferences of a small population of Asian elephants in Nangunhe National Nature Reserve in Yunnan, China, during the annual dry season. The next-generation sequencing of the rbcL gene from non-invasively collected fecal samples was conducted in addition to transect surveys and camera-trapping along known elephant trails. With the transect survey, we identified 31 plant species foraged by elephants. The next-generation sequencing analysis identified a total of 90 plant species from the elephant dung samples. Only nine species were detected at rates greater than 1% in all the samples. Poaceae (47.69%), Moraceae (21.25%), and Musaceae (11.24%) were detected to have the highest rates at the family level. We also examined whether differences existed between sexes, age groups, and individuals; however, significant differences were found only between individuals. This study provides useful insights into the foraging preferences of Asian elephants, which could help in further understanding the interactions between elephants and their habitat in the reserve and inform future management decisions in related areas. The detected core plant species with relatively high abundance could provide guidance for habitat restoration and cultivation of food bases. The local plantations where the elephants prefer to feed could be moved farther away, making them inaccessible to the elephants.