History, challenges, and prospects of researches on fish functional diversity.

To complete the life cycle, species exhibit corresponding functional traits in morphology, physiology, ecology, etc. The eigenvalues, variation, and distribution of functional traits are the functional components of biodiversity, namely functional diversity, could maintain the service function and healthy operation of ecosystems. The application of functional diversity broadens our understanding of biodiversity and its temporal and spatial variations, and provides a breakthrough to the problem of how to combine morphological structure with ecological function. I reviewed the research process of functional diversity from the perspective of proposing, calculating, and applying the parameters of functional diversity, as well as the application of functional diversity from different purposes and perspectives. I put forward the challenges and countermeasures of related studies. In the future, researches should pay attention to establish a set of effective trait indicators, discover the internal and external mechanisms driving functional diversity variations, and map the redistribution of traits under environmental changes.