Diet drives the gut microbiome composition and assembly processes in winter migratory birds in the Poyang Lake wetland, China

Exploring Bird Gut Microbiota Through Opportunistic Fecal Sampling: Ecological and Evolutionary Perspectives

Wetland ecosystems are facing alarming rates of destruction and degradation, posing significant challenges for avian populations reliant on these habitats. Bird health is closely linked to the composition of their intestinal microbiota, which is primarily influenced by local conditions, primarily through diet. Building on our previous work identifying dietary variations among bird populations in marshes within a Ramsar site along the Somme and Avre rivers (France), this pilot study aimed to assess the relevance of using fecal samples collected from the ground to characterize avian intestinal microbiota via 16S rRNA metabarcoding. We hypothesized that this noninvasive sampling method would capture how bird traits and environmental factors shape fecal microbiota composition. Sampling was conducted during the breeding season at seven locations (six within the Ramsar site and one on its outskirts) spanning rural or peri-urban environments. A total of 52 fecal samples from nine bird species or families, predominantly waterbirds, were analyzed for bacterial composition. At the phylum level, Firmicutes and Proteobacteria were predominant, with the relative abundance of genera such as Clostridium, Rothia, Bacillus, Caldilinea and Pseudomonas varying among bird species. The potential enteropathogen Campylobacter was primarily detected in samples from peri-urban sites. Multivariate analyses revealed significant variations in bacterial composition associated with bird trophic guild, ecology, body length, pond surface and habitat location. Additionally, a weak correlation was observed between host phylogeny and microbiota composition. Although the limited sample size, particularly for some species, constrains the robustness of these findings, the observed trends align with ecological expectations. This study highlights the potential of opportunistically collected fecal samples as a low-impact tool for exploring the relationship between bird gut microbiota and their habitat.

Annual cycle variations in the gut microbiota of migratory black-necked cranes

Introduction

Migratory birds exhibit unique annual cycles that complicate their gut microbiota. However, the annual dynamics of gut microbiota in migratory birds remain unclear, hindering our understanding of their environmental adaptation.

Methods

Here, we collected fecal samples from black-necked cranes (Grus nigricollis) across four seasons at their breeding grounds and used wintering ground data from databases to characterize their gut microbial compositions throughout the year.

Results and discussion

The results showed that the gut microbiota was clustered by season (Bray-Curtis: R 2 = 0.348, p < 0.001; UniFrac: R 2 = 0.352, p < 0.001). And the summer samples exhibited higher alpha (Simpson and Shannon), beta diversity (Bray-Curtis and UniFrac) and more diverse functions in gut microbiota compared to other seasons. Furthermore, in summer, the gut microbiota exhibited several balanced relative abundances at the family level, whereas Lactobacillaceae family dominated during the other seasons. Thirty-six ASVs were identified by random forest analysis to distinguish samples from distinct seasons. Despite having greater diversity, the summer gut microbiota had a simpler network structure than the other seasons (fewer edges and nodes). The dispersal limitation during random processes also significantly influenced gut microbial community assembly. Overall, the gut microbiota of the black-necked crane undergoes dynamic adjustments to adapt to seasonal environmental changes, which may be associated with the variations in diet across seasons. These results enhance our understanding of the gut microbiota of wild migratory birds and support further research on black-necked cranes.

Comparative analysis of the gut bacteria and fungi in migratory demoiselle cranes (Grus virgo) and common cranes (Grus grus) in the Yellow River Wetland, China

Introduction

Gut microbiota are closely related to the nutrition, immunity, and metabolism of the host and play important roles in maintaining the normal physiological activities of animals. Cranes are important protected avian species in China, and they are sensitive to changes in the ecological environment and are thus good environmental indicators. There have been no reports examining gut fungi or the correlation between bacteria and fungi in wild Demoiselle cranes (Grus virgo) and Common cranes (Grus grus). Related research can provide a foundation for the protection of rare wild animals.

Methods

16S rRNA and ITS high-throughput sequencing techniques were used to analyze the gut bacterial and fungal diversity of Common and Demoiselle cranes migrating to the Yellow River wetland in Inner Mongolia.

Results

The results revealed that for gut bacteria α diversity, Chao1 index in Demoiselle cranes was remarkably higher than that in Common cranes (411.07 ± 79.54 vs. 294.92 ± 22.38), while other index had no remarkably differences. There was no remarkable difference in fungal diversity. There were marked differences in the gut microbial composition between the two crane species. At the phylum level, the highest abundance of bacteria in the Common crane and Demoiselle crane samples was Firmicutes, accounting for 87.84% and 74.29%, respectively. The highest abundance of fungi in the guts of the Common and Demoiselle cranes was Ascomycota, accounting for 69.42% and 57.63%, respectively. At the genus level, the most abundant bacterial genus in the Common crane sample was Turicibacter (38.60%), and the most abundant bacterial genus in the Demoiselle crane sample was Catelicoccus (39.18%). The most abundant fungi in the Common crane sample was Penicillium (6.97%), and the most abundant fungi in the Demoiselle crane sample was Saccharomyces (8.59%). Correlation analysis indicated that there was a significant correlation between gut bacteria and fungi.

Discussion

This study provided a research basis for the protection of cranes. Indeed, a better understanding of the gut microbiota is very important for the conservation and management of wild birds, as it not only helps us to understand their life history and related mechanisms, but also can hinder the spread of pathogenic microorganisms.

Are fecal samples an appropriate proxy for amphibian intestinal microbiota?

The intestinal microbiota, an invisible organ supporting a host's survival, has essential roles in metabolism, immunity, growth, and development. Since intestinal microbiota influences a host's biology, application of such data to wildlife conservation has gained interest. There are standard protocols for studying the human intestinal microbiota, but no equivalent for wildlife. A major challenge is sampling the intestinal microbiota in an effective, unbiased way. Fecal samples are a popular proxy for intestinal microbiota because collection is non-invasive and allows for longitudinal sampling. Yet it is unclear whether the fecal microbiota is representative of the intestinal microbiota. In wildlife studies, research on the sampling methodology is limited. In this study focusing on amphibians, we characterize and compare the microbiota (small intestine, large intestine, and feces) of two Hong Kong stream-dwelling frog species: Lesser Spiny Frog (Quasipaa exilispinosa) and Hong Kong Cascade Frog (Amolops hongkongensis). We found that the microbiota of both species are similar at the level of phylum and family, but diverge at the level of genus. When we assessed the performance of fecal microbiota in representing the intestinal microbiota in these two species, we found that (1) the microbiota of the small and large intestine differs significantly, (2) feces are not an appropriate proxy of either intestinal sections, and (3) a set of microbial taxa significantly differs between sample types. Our findings raise caution equating fecal and intestinal microbiota in stream-dwelling frogs. Sampling feces can avoid sacrifice of an animal, but researchers should avoid over-extrapolation and interpret results carefully.

Comparative analysis of the gut microbiota of wild wintering whooper swans (Cygnus Cygnus), captive black swans (Cygnus Atratus), and mute swans (Cygnus Olor) in Sanmenxia Swan National Wetland Park of China

The gastrointestinal microbiota, a complex ecosystem, is involved in the physiological activities of hosts and the development of diseases. Birds occupy a critical ecological niche in the ecosystem, performing a variety of ecological functions and possessing a complex gut microbiota composition. However, the gut microbiota of wild and captive birds has received less attention in the same region. We profiled the fecal gut microbiome of wild wintering whooper swans (Cygnus Cygnus; Cyg group, n = 25), captive black swans (Cygnus Atratus; Atr group, n = 20), and mute swans (Cygnus Olor; Olor group, n = 30) using 16S rRNA gene sequencing to reveal differences in the gut microbial ecology. The results revealed that the three species of swans differed significantly in terms of the alpha and beta diversity of their gut microbiota, as measured by ACE, Chao1, Simpson and Shannon indices, principal coordinates analysis (PCoA) and non-metricmulti-dimensional scaling (NMDS) respectively. Based on the results of the linear discriminant analysis effect size (LEfSe) and random forest analysis, we found that there were substantial differences in the relative abundance of Gottschalkia, Trichococcus, Enterococcus, and Kurthia among the three groups. Furthermore, an advantageous pattern of interactions between microorganisms was shown by the association network analysis. Among these, Gottschalkia had the higher area under curve (AUC), which was 0.939 (CI = 0.879-0.999), indicating that it might be used as a biomarker to distinguish between wild and captive black swans. Additionally, PICRUSt2 predictions indicated significant differences in gut microbiota functions between wild and captive trumpeter swans, with the gut microbiota functions of Cyg group focusing on carbohydrate metabolism, membrane transport, cofactor, and vitamin metabolism pathways, the Atr group on lipid metabolism, and the Olor group on cell motility, amino acid metabolism, and replication and repair pathways. These findings showed that the gut microbiota of wild and captive swans differed, which is beneficial to understand the gut microecology of swans and to improve regional wildlife conservation strategies.

The succession of gut microbiota in the concave-eared torrent frog (Odorrana tormota) throughout developmental history

The gut microbiota of amphibians plays a crucial role in maintaining health and adapting to various developmental stages. The composition of gut microbial community is influenced by the phylogeny, habitat, diet, and developmental stage of the host. The present study analyzed the microbiota in the intestine of O. tormota at 11 developmental stages (from the tadpole at Gosner stage 24 to the 3-year-old adult) using high-throughput 16S rRNA sequencing. Alpha diversity index analysis of the microbiota revealed that the index decreased from tadpole at Gosner stage 24 to adult frog stage, remained stable during the adult frog stages, but increased significantly at the early metamorphosis and hibernation preparation stages. The gut microbiota structure is similar in adult frogs but differs significantly in other developmental stages. Furthermore, the dominant phyla of gut microbiota in tadpoles were Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes, whereas those in adult frogs were Proteobacteria, Firmicutes, Bacteroidetes, and Verrucomicrobia. Host and environmental factors jointly affected the gut microbial diversity and community composition of O. tormota, but developmental stage, feeding habit, and habitat type had a more significant influence. The microbial community in the gut varies with the developmental stage of the host and constantly adapts to the survival requirements of the host. These findings advance our understanding of the evolutionary mechanism of amphibian gut microbiota in maintaining health homeostasis and adaptation.