The article explores the diversity and evolution of chemoreceptor gene families in vertebrates, revealing significant variations in the number and composition of these genes across different species. Six families of G protein-coupled receptors (GPCRs) are central to chemoreception: olfactory receptors (OR), trace amine-associated receptors (TAAR), vomeronasal receptors (V1R and V2R), and taste receptors (T1R and T2R). By analyzing 1,527 vertebrate genomes, the study finds that amphibians have the largest chemoreceptor repertoires, followed by mammals and turtles. The number of OR genes correlates with habitat in mammals and birds, and with migratory behavior in birds. Taste receptor repertoires correlate with diet in mammals and with aquatic environments in fish. The study highlights that chemoreceptor gene families are co-evolving, dynamic, and exhibit lineage-specific expansions and losses. For example, OR genes are expanded in tetrapods, TAAR and T1R in teleosts, V1R in mammals, and V2R and T2R in amphibians. Amphibians have the most extensive taste receptor gene repertoire, while marine tetrapods show a convergent reduction in chemoreceptor numbers. The evolution of these genes is influenced by ecological and morphological factors, with amphibians, due to their semi-aquatic lifestyle, having a larger repertoire of chemoreceptor genes. The study also reveals that the number of OR genes is positively correlated with the size of the olfactory bulb in birds and mammals, and with the number of lamellae in the olfactory epithelium in ray-finned fishes. The number of TAAR genes is also positively correlated with the relative size of the olfactory bulb in mammals. The evolution of taste receptors (T1R and T2R) is influenced by diet, with omnivores having the highest number of T2R genes. However, this association is not true for ray-finned fishes or birds and crocodiles. The transition to a marine lifestyle has a significant impact on the number of chemoreceptor genes in tetrapods, with marine species generally having a reduced repertoire. For example, cetaceans and pinnipeds lack T1R genes, while sirenians, which are herbivorous and marine, still have T1R genes. The study suggests that T1R losses in marine mammals may be associated with dietary adaptations rather than high sodium concentrations in oceans. Overall, the study provides insights into the ecological and morphological factors driving the evolution of chemoreceptor gene repertoires in vertebrates, emphasizing the importance of considering both olfactory and taste receptors together. The dataset and gene mining procedure presented will be valuable for future research on chemoreception in vertebrates.The article explores the diversity and evolution of chemoreceptor gene families in vertebrates, revealing significant variations in the number and composition of these genes across different species. Six families of G protein-coupled receptors (GPCRs) are central to chemoreception: olfactory receptors (OR), trace amine-associated receptors (TAAR), vomeronasal receptors (V1R and V2R), and taste receptors (T1R and T2R). By analyzing 1,527 vertebrate genomes, the study finds that amphibians have the largest chemoreceptor repertoires, followed by mammals and turtles. The number of OR genes correlates with habitat in mammals and birds, and with migratory behavior in birds. Taste receptor repertoires correlate with diet in mammals and with aquatic environments in fish. The study highlights that chemoreceptor gene families are co-evolving, dynamic, and exhibit lineage-specific expansions and losses. For example, OR genes are expanded in tetrapods, TAAR and T1R in teleosts, V1R in mammals, and V2R and T2R in amphibians. Amphibians have the most extensive taste receptor gene repertoire, while marine tetrapods show a convergent reduction in chemoreceptor numbers. The evolution of these genes is influenced by ecological and morphological factors, with amphibians, due to their semi-aquatic lifestyle, having a larger repertoire of chemoreceptor genes. The study also reveals that the number of OR genes is positively correlated with the size of the olfactory bulb in birds and mammals, and with the number of lamellae in the olfactory epithelium in ray-finned fishes. The number of TAAR genes is also positively correlated with the relative size of the olfactory bulb in mammals. The evolution of taste receptors (T1R and T2R) is influenced by diet, with omnivores having the highest number of T2R genes. However, this association is not true for ray-finned fishes or birds and crocodiles. The transition to a marine lifestyle has a significant impact on the number of chemoreceptor genes in tetrapods, with marine species generally having a reduced repertoire. For example, cetaceans and pinnipeds lack T1R genes, while sirenians, which are herbivorous and marine, still have T1R genes. The study suggests that T1R losses in marine mammals may be associated with dietary adaptations rather than high sodium concentrations in oceans. Overall, the study provides insights into the ecological and morphological factors driving the evolution of chemoreceptor gene repertoires in vertebrates, emphasizing the importance of considering both olfactory and taste receptors together. The dataset and gene mining procedure presented will be valuable for future research on chemoreception in vertebrates.