Comparative genomics sheds light on the predatory lifestyle of accipitrids and owls

Raptors are carnivorous birds including accipitrids (Accipitridae, Accipitriformes) and owls (Strigiformes), which are diurnal and nocturnal, respectively. To examine the evolutionary basis of adaptations to different light cycles and hunting behavior between accipitrids and owls, we de novo assembled besra (Accipiter virgatus, Accipitridae, Accipitriformes) and oriental scops owl (Otus sunia, Strigidae, Strigiformes) draft genomes. Comparative genomics demonstrated four PSGs (positively selected genes) (XRCC5, PRIMPOL, MDM2, and SIRT1) related to the response to ultraviolet (UV) radiation in accipitrids, and one PSG (ALCAM) associated with retina development in owls, which was consistent with their respective diurnal/nocturnal predatory lifestyles. We identified five accipitrid-specific and two owl-specific missense mutations and most of which were predicted to affect the protein function by PolyPhen-2. Genome comparison showed the diversification of raptor olfactory receptor repertoires, which may reflect an important role of olfaction in their predatory lifestyle. Comparison of TAS2R gene (i.e. linked to tasting bitterness) number in birds with different dietary lifestyles suggested that dietary toxins were a major selective force shaping the diversity of TAS2R repertoires. Fewer TAS2R genes in raptors reflected their carnivorous diet, since animal tissues are less likely to contain toxins than plant material. Our data and findings provide valuable genomic resources for studying the genetic mechanisms of raptors' environmental adaptation, particularly olfaction, nocturnality and response to UV radiation.