chromosomal rearrangements

Reference genomes and fossils revise bat family phylogeny and biogeography
Bats are extraordinary among mammals, having uniquely evolved powered flight and laryngeal echolocation, along with disease resistance, extended healthspans and the ability to hibernate1. However, the evolutionary history of bats and the understanding of these adaptations remain unresolved. We analysed chromosome-level, long-read genome assemblies from 103 bat species, including 42 new assemblies, representing all 21 bat families. This dataset, expanded in scope and assembly quality, yielded a new bat phylogeny. We placed Myzopodidae as the earliest branch within Vespertilionoidea, and resolved yangochiropteran relationships, identifying Emballonuroidea and Vespertilionoidea as sister groups. Our analysis revealed a mosaic evolutionary history across bats and explained why previous phylogenetic studies were misled. Chromosomal ancestral-state reconstructions supported 26 ancestral bat chromosomes. We integrated a morphological dataset of 699 characters for 65 species, including 44 pre-Quaternary fossils and representatives of most living bat families, with neutrally evolving genomic sites. Fossilized birth–death and dispersal–extinction cladogenesis analyses showed that bats, and thus powered flight, probably originated in Europe in the late Palaeocene, refuting African and North American origins. Placement of the fossil †Vielasia in the oldest ‘Eochiroptera’ clade indicates that laryngeal echolocation predates crown-bat diversification. Total evidence dating, including the fossil taxa, significantly reduced unrepresented basal branch lengths compared with molecular-only divergence estimates. By integrating comprehensive genomic and morphological datasets, analysed using innovative methods, we resolve long-standing controversies in bat biology and provide new insights into the evolutionary history and trait diversification of bats.
Genomic comparisons and the adaptive basis of brain size plasticity and chromosomal instability in the Eurasian common shrew
Sorex araneus, the Eurasian common shrew, has seasonal brain size plasticity (Dehnel’s phenomenon) and abundant intraspecific chromosomal rearrangements, but genomic contributions to these traits remain unknown. We couple a chromosome-scale genome assembly with seasonal brain transcriptomes to discover relationships between molecular changes and both traits. Positively selected genes enriched the Fanconi anemia DNA repair pathway, which prevents the accumulation of chromosomal aberrations, and is likely involved in chromosomal rearrangements (FANCI, FAAP100). Genes involved in neurogenesis show either signatures of positive selection (PCDHA6), seasonal differential expression in the cortex and hippocampus (Notch signaling), or both (SOX9), suggesting a role for cellular proliferation in seasonal brain shrinkage and regrowth. Both positive selection and evolutionary upregulation in the shrew hypothalamus of VEGFA and SPHK2 indicate adaptations in hypothalamic metabolic homeostasis have evolved together with Dehnel’s phenomenon. These findings reveal genomic changes central to the evolution of both chromosomal instability and cyclical patterns in brain gene expression that characterizes mammalian brain size plasticity.