Millions of migratory birds occupy seasonally favourable breeding grounds in the Arctic 1 , but we know little about the formation, maintenance and future of Arctic bird migration routes and genetic determinants of migratory distance. Here, we established a continental-scale migration system, satellite tracking 56 peregrine falcons (Falco peregrinus) from six Eurasian Arctic breeding populations and resequencing 35 genomes from four of these. Different breeding populations used five migration routes across Eurasia, likely formed by longitude and latitude breeding ground shifts during the LGM-Holocene transition. Contemporary inter-route environmental divergence appears to maintain distinct migration routes. We found that the novel gene ADCY8 was associated with population-level migratory distance differences. We elucidated its regulatory mechanism and found the most likely selective agent for this divergence was long-term memory. Global warming is predicted to influence migration strategies and diminish breeding ranges of Eurasian Arctic peregrines. Harnessing ecological interactions and evolutionary processes to study climate-driven changes in migration can facilitate the conservation of migratory birds.
The Southern catfish (Silurus meridionalis) is a nocturnal and benthic freshwater fish endemic to the Yangtze River and its tributaries. In this study, we constructed a chromosome-level draft genome of S. meridionalis using 69.7-Gb Nanopore long reads and 49.5-Gb Illumina short reads. The genome assembly was 741.2 Mb in size with a contig N50 of 13.19 Mb. An additional 116.4 Gb of Bionano and 77.4 Gb of Hi-C data were applied to assemble contigs into scaffolds and further into 29 chromosomes, resulting in a 738.9-Mb genome with a scaffold N50 of 28.04 Mb. A total of 22,965 protein-coding genes were predicted from the genome with 22,519 (98.06%) genes functionally annotated. Comparative genomic and transcriptomic analyses revealed a rod-dominated visual system which was responsible for scotopic vision. The absence of cone opsins SWS1 and SWS2 resulted in the lack of ultraviolet and blue violet sensitivity. Mutations at key amino acid sites of RH1.1, RH1.2 and RH2 resulted in spectral tuning good for dim light vision and narrow colour vision. A higher expression level of rod phototransduction genes than that of cone genes and higher rod-to-cone ratio led to higher optical sensitivity under dim light conditions. In addition, analysis of the genes involved in eye morphogenesis and development revealed the loss of some conserved noncoding elements, which might be associated with the small eyes in catfish. Together, our study provides important clues for the adaptation of the catfish visual system to the nocturnal and benthic lifestyles. The draft genome of S. meridionalis represents a valuable resource for studies of the molecular mechanisms of ecological adaptation.
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