Aim Exploring the mechanism underlying community assembly processes is considered as one of the central topics for biogeography. As one of the biodiversity hotspots, Nepal Himalaya has attracted increasing attention during the past decade. However, the main processes shaping amphibian assemblages in this area are still unclear. Here, we examined the elevational patterns of amphibian functional and phylogenetic structures to understand the main mechanism driving amphibian assemblages along an elevational gradient in eastern Nepal Himalaya. Location Eastern Nepal Himalaya. Methods Amphibian taxonomic, functional and phylogenetic diversity were calculated, and their responses to the increasing elevations were investigated based on the linear regressions. The environmental determinants of amphibian diversity were revealed based on the incorporation of generalized linear models and hierarchical partitioning analyses. In addition, the mechanism driving amphibian assemblages from low to high elevations was tested by calculating the mean pairwise functional distance and the mean pairwise phylogenetic distance indices. Results Amphibian taxonomic, functional and phylogenetic diversity had contrast responses to the increasing elevations, which were strongly determined by variables such as air temperature, the number of trees, leaf litter cover and water pH. Interestingly, the trends of amphibian functional and phylogenetic diversity along an elevational gradient can be changed after controlling the effects of species richness. Moreover, determining process played a dominant role in shaping amphibian assemblages with the increasing elevations. Conclusions Our results revealed the elevational patterns of amphibian functional and phylogenetic structures in eastern Nepal Himalaya, associated with the change in environmental variables. We also highlighted the dominant role of determining process in shaping amphibian assemblages. Overall, our results can help ecologists and managers better understand and formulate amphibian diversity conservation. In addition, our results also enriched the fundamental knowledge to understand the general patterns of community assembly rules in montane ecosystems.

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The Chinese giant salamander (Andrias davidianus), one of the largest extant amphibian species, has dramatically declined in the wild. As an ectotherm, it may be further threatened by climate change. Therefore, understanding the thermal physiology of this species should be the priority to formulate related conservation strategies. In this study, the plasticity in metabolic rate and thermal tolerance limits of A. davidianus larvae were studied. Specifically, the larvae were acclimated to three temperature levels (7 °C, cold stress; 15 °C, optimum; and 25 °C, heat stress) and two diet items (red worm or fish fray) for 20 days. Our results indicated that cold-acclimated larvae showed increased metabolic capacity, while warm-acclimated larvae showed a decrease in metabolic capacity. These results suggested the existence of thermal compensation. Moreover, the thermal tolerance windows of cold-acclimated and warm-acclimated larvae shifted to cooler and hotter ranges, respectively. Metabolic capacity is not affected by diet but fish-fed larvae showed superiority in both cold and heat tolerance, potentially due to the input of greater nutrient loads. Overall, our results suggested a plastic thermal tolerance of A. davidianus in response to temperature and diet variations. These results are meaningful in guiding the conservation of this species.

The reintroduction of captive-bred individuals is a primary approach to rebuild the wild populations of the Chinese giant salamander (Andrias davidianus), the largest extant amphibian species. However, the complexity of the wild habitat (e.g., diverse microorganisms and potential pathogens) potentially threatens the survival of reintroduced individuals. In this study, fresh (i.e., containing environmental microbiota) or sterilized river sediments (120°C sterilized treatment) were added to the artificial habitats to treat the larvae of the Chinese giant salamander (control group—Cnt: 20 individuals, treatment group 1 with fresh river sediments—T1: 20 individuals, and treatment group 2 with sterilized river sediments—T2: 20 individuals). The main objective of this study was to test whether this procedure could provoke their wild adaptability from the perspective of commensal microbiotas (skin, oral cavity, stomach, and gut) and larvae transcriptomes (skin, spleen, liver, and brain). Our results indicated that the presence of habitat sediments (whether fresh or sterilized) reshaped the oral bacterial community composition. Specifically, Firmicutes decreased dramatically from ~70% to ~20–25% (mainly contributed by Lactobacillaceae), while Proteobacteria increased from ~6% to ~31–36% (mainly contributed by Gammaproteobacteria). Consequently, the proportion of antifungal operational taxonomic units (OTUs) increased, and the function of oral microbiota likely shifted from growth-promoting to pathogen defense. Interestingly, the skin microbiota, rather than the colonization of habitat microbiota, was the major source of the pre-treated oral microbiota. From the host perspective, the transcriptomes of all four organs were changed for treated individuals. Specifically, the proteolysis and apoptosis in the skin were promoted, and the transcription of immune genes was activated in the skin, spleen, and liver. Importantly, more robust immune activation was detected in individuals treated with sterilized sediments. These results suggested that the pathogen defense of captive-bred individuals was improved after being treated, which may benefit their survival in the wild. Taken together, our results suggested that the pre-exposure of captive-bred Chinese giant salamander individuals to habitat sediments could be considered and added into the reintroduction processes to help them better adapt to wild conditions.