Reporters learned from the Kunming Institute of Zoology, Chinese Academy of Sciences, on the 20th that Lai Ren's research team has made important achievements in understanding the key mechanism of bird taste adaptation, which not only reveals the mechanism of subtle adaptation of animal senses to the environment, but also provides important scientific clues for in-depth understanding of the co evolutionary relationship between birds and plants, and the adaptation strategies of organisms to the environment, and has a far-reaching impact on deepening understanding of the formation mechanism of biodiversity. The relevant research results were published on June 20th in the international journal Science. Sour taste is often seen by mammals as a warning signal of potential harmful substances, however, many birds are able to frequently consume acidic fruits rich in high concentrations of organic acids, and their tolerance mechanisms have long been unresolved. In response to this scientific challenge, Lai Ren's team conducted in-depth research. Research has shown that the core of birds' unique adaptive ability lies in the functional evolution of their acid taste receptor OTOP1. The research team analyzed the adaptive evolution process of the OTOP1 receptor in birds and found that the receptor underwent a critical functional transformation, significantly enhancing birds' acid tolerance. This enabled birds to effectively feed on acidic fruits, thereby expanding their food sources and occupying a broader ecological niche. Further research has found that the OTOP1 receptor of the songbird group in birds has undergone a single amino acid residue mutation. This ingenious evolutionary strategy effectively enhances the songbird group's acid tolerance. In addition, the research team also revealed a potential co evolutionary mechanism between the sourness tolerance and sweetness perception abilities of birds. This synergistic effect enables birds to not only effectively tolerate high organic acids in fruits, but also keenly perceive the sugar content, i.e. sweetness, in them, thus more efficiently developing and utilizing fruit resources. This study systematically reveals for the first time the molecular mechanisms of bird perception and tolerance of sourness, as well as their key roles in the evolutionary process. It clarifies that the functional evolution of OTOP1 receptors is another key molecular basis driving bird dietary expansion, niche occupation, and rapid species radiation evolution. The hypothesis of "co evolution of sourness tolerance and sweet taste perception in songbirds" provides a new perspective for understanding how complex sensory systems co evolve to adapt to the environment. (New Society)