Distribution pattern and driving factors of genetic diversity of passerine birds in the Mountains of Southwest China

Genetic diversity is one of the three dimensions of biodiversity and fundamental to various life forms on the Earth.Understanding the distribution pattern of genetic diversity and its driving forces has been an important topic in ecology,biogeography and conservation biology since the last decade.We investigated the genetic diversity pattern of passerine birds in the Mountains of Southwest China,a global biodiversity hotspot with the highest species richness of birds in the entire Eurasia,and explored the influencing forces of environmental variables on genetic diversity.We compiled 1189 Cytochrome b sequences of 27 passerine species from 152 geographic sites,covering the range of Mountains of Southwest China and its adjoining areas.We generated genetic diversity distribution maps using a grid-cell method based on nucleotide diversity and haplotype diversity indices.We further analyzed the variation pattern of the two indices along latitudinal,longitudinal,and elevational gradients.The correlations between the two indices and environmental variables were also evaluated.The nucleotide diversity hotspots were mostly located in the southern Hengduan Mountains,while for haplotype diversity,three hotspots were detected:the southeast edge of the Qinghai-Tibetan Plateau,the southern Hengduan Mountains and the Qinling Mountains.There was no monotonic increasing or decreasing pattern in nucleotide diversity or haplotype diversity along latitudinal,longitudinal or elevational gradients except for altitudinal range.Correlation and model selection analyses detected multiple environmental variables in driving genetic diversity patterns,including temperature,precipitation,vegetation,human influence,longitude and altitude range.Similar to the pattern of species richness,the nucleotide diversity pattern of passerine birds in the Mountains of Southwest China presents a decreasing trend from southwest to northeast,while the haplotype diversity pattern is more likely decreased from west to east.Our results indicate that the distribution pattern of genetic diversity may be derived from the complex topography and diverse microclimates in the Mountains of Southwest China.

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.