Metabolic and microbial changes in light-vented bulbul during recent northward range expansion

Endotherms recently expanding to cold environments generally exhibit strong physiological acclimation to sustain high body temperature.During this process,gut microbes likely play a considerable role in host physiological functions,including digestion and thermogenesis.The light-vented bulbul Pycnonotus sinensis represents one such species.It used to be restricted to the Oriental realm but expanded its distribution range north to the Palearctic areas during the past few decades.Here,we explored the seasonal dynamics of the resting metabolic rate(RMR)and microbiota for local and newly colonized populations of the species.Our results showed that the mass-adjusted RMR and body mass were pos-itively correlated with latitude variations in both seasons.Consistently,the gut microbiota showed a corresponding variation to the northern cold environments.In the two northern populations,the alpha diversity decreased compared with those of the two southern populations.Significant differences were detected in dominant phyla,such as Firmicutes,Bacteroidetes,Proteobacteria,and Desulfobacterota in both seasons.The core microbiota showed geographic differences in the winter,including the elevated relative abundance of 5 species in northern populations.Finally,to explore the link between microbial communities and host metabolic thermogenesis,we conducted a correlation analysis between microbiota and mass-adjusted RMR.We found that more genera were significantly correlated with mass-adjusted RMR in the wintering season compared to the breeding season(71 vs.23).These results suggest that microbiota of the lighted-vented bulbul linked with thermogenesis in diversity and abundance under northward expansion.

Avian lower beak is always overlooked:its coordinate role in shaping species-specific beak should not be underestimated

The beak is a key evolutionary innovation in the avian tree of life.Its diversity in morphology shows birds’successful colonization of various ecological niches on the Earth(Pigot et al.2020),and its morphological plasticity can also enable birds to rapidly respond to changes in environments(Grant&Grant 2006).These natures helped birds survive multiple extinction events(Larson et al.2016).Therefore,investigating the morphological evolution of avian beaks and the underlying developmental and molecular mechanisms will help to decipher the evolution of birds and boost the development of the theory of evolutionary biology.

Comparative transcriptomic and metabolomic analysis reveals pectoralis highland adaptation across altitudinal songbirds

Pectoralis phenotypic variation plays a fundamental role in locomotion and thermogenesis in highland birds.How-ever,its regulatory and metabolic mechanisms remain enigmatic to date.Here,we integrated phenomic,tran-scriptomic,and metabolomic approaches to determine muscle variation and its underpinning mechanisms across altitudinal songbirds.Phenomics confirmed that all highland birds had considerable increases in muscle oxidative capacity,capillarity,and mitochondrial abundance in our study.Correspondingly,transcriptomic analyses found that differentially expressed genes in phenotype-associated modules enriched for blood vessel,muscle structure development,and mitochondrial organization.Despite similar traits and functional enrichments across highland birds,different mechanisms drove their occurrence in high-altitude tree sparrow and 2 snowfinches.Importantly,a metabolic feature shared by all the 3 highland birds is the improvement in insulin sensitivity and glucose utilization through activating insulin signaling pathway,which is vital to increase muscle oxidative capacity and maintain metabolic homeostasis.Nevertheless,fatty acid biosynthesis and oxidation are enhanced in only 2 snowfinches which had a long evolutionary history on the high plateau,also differing from ketone body metabolism in recently introduced colonizer of the tree sparrow of the high plateau.Our study represents a vital contribution to reveal the regulatory and metabolic basis of pectoralis variation across altitudinal songbirds.