Evolução do reconhecimento de espécies por pistas sociais e fenotípicas em um complexo de espécies de peixes amazônicos

Abstract

Fish are notorious organisms for the ability to form cohesive groups of individuals of the same species (shoals). Schooling often involves the use of morphological similarities, i.e. individuals may cluster by identifying others of similar morphology to swim toward them. The evolution of this remarkable gregarious behavior in fish has a strong importance in relation to the risk of death by predation: shoals are safer for individuals to avoid predator attacks. In fact, the grouping process can be influenced by the presence of a potential predator. Therefore, the individual benefit in the formation of schools is increased by the capacity of recognition of co-specific individuals. Species recognition can evolve rapidly from social aggregation mechanisms in which individuals only approach other individuals with similar morphology, which typically occurs through predation pressure. The ability of individuals to discriminate individuals of the species itself and of different species, that is, the evolution of species recognition can occur in two ways: reinforcement or pleiotropy. In this work we studied the fish species Crenuchus spilurus (Characiformes: Crenuchidae) and we suggest that the ability of individuals of different strains to segregate when inserted in the same environment would be indicative of the existence of coespecific recognition from an early stage of the speciation. Additionally, we have seen that females of both strains recognize and aggregate after a certain time, since they are not adept at recognizing themselves readily. Recognition and aggregation among individuals of the same lineage are mediated by the use of visual or behavioral clues rather than by the time of coexistence, but they are still not very evident to the researchers.