Search

Adaptations can endow species with complex traits that enable them to occupy new niches. To adapt to the arboreal lifestyle, treefrogs have evolved a suite of complex traits for climbing and gliding; to date, however, the molecular mechanisms underpinning these adaptations are unknown. Here, based on two de novo-assembled Asian treefrog genomes, genes related to limb development showed evidence of accelerated evolution. Furthermore, the PPL gene that regulates the keratin cytoskeleton showed conservative substitution within the genus Rhacophorus. These genetic changes contribute to limb and toe-pad morphogenesis, providing fundamental adaptations for climbing and grasping. Behavioral and morphological comparisons clarified the gliding function of interdigital webbing and the different developmental patterns between fully and weakly webbed feet. Time-ordered gene coexpression network analysis of gliding Rhacophorus kio and nongliding Rhacophorus dugritei tadpoles revealed specific coexpression patterns for fully webbed feet, which involved the Wnt signaling and vascular remodeling pathways. These findings highlight the molecular basis of phenotypes that facilitate expansion into new niches and provide insights into the importance of local adaptation in shaping phenotypes and locomotion patterns. [ABSTRACT FROM AUTHOR]

Several previous genomic studies have focused on adaptation to high elevations, but these investigations have been largely limited to endotherms. Snakes of the genus Thermophis are endemic to the Tibetan plateau and therefore present an opportunity to study high-elevation adaptations in ectotherms. Here, we report the de novo assembly of the genome of a Tibetan hot-spring snake (Thermophis baileyi) and then compare its genome to the genomes of the other two species of Thermophis, as well as to the genomes of two related species of snakes that occur at lower elevations. We identify 308 putative genes that appear to be under positive selection in Thermophis. We also identified genes with shared amino acid replacements in the high-elevation hot-spring snakes compared with snakes and lizards that live at low elevations, including the genes for proteins involved in DNA damage repair (FEN1) and response to hypoxia (EPAS1). Functional assays of the FEN1 alleles reveal that the Thermophis allele is more stable under UV radiation than is the ancestral allele found in low-elevation lizards and snakes. Functional assays of EPAS1 alleles suggest that the Thermophis protein has lower transactivation activity than the low-elevation forms. Our analysis identifies some convergent genetic mechanisms in high-elevation adaptation between endotherms (based on studies of mammals) and ectotherms (based on our studies of Thermophis). [ABSTRACT FROM AUTHOR]