EVOLUÇÃO DA ICTIOFAUNA DE RIACHOS SUL-AMERICANOS (CASTRO, 1999) REVISITADO APÓS MAIS DE DUAS DÉCADAS

Abstract

A little more than 20 years after the first publication of Castro (1999), the knowledge of the South American freshwater ichthyofauna, especially that of Brazil, has increased dramatically. This increase occurred both in terms of knowledge of its taxonomic diversity - in 1999, based on various sources in the scientific literature, a total of 2,800 species of South American freshwater fish was estimated, and a total of near 3,500 species it is currently known from Brazil alone - as to the knowledge of its evolution and also ecology. Consequently, all the hypotheses originally proposed in that paper are reexamined and critically discussed here considering this new knowledge accumulated in the past nearly two decades. Although the original 1999 hypothesis that the small adult size of their respective species is a general evolutionary pattern shared by the South American stream ichthyofauna has been firmly corroborated by several studies carried out in many regions of Brazil, the different patterns associated with most of the species of stream fish originally proposed are discussed in this chapter in the light of the new accumulated knowledge about their biology and ecology. Likewise, the possible role of heterochrony in their respective evolution is critically analyzed in the context of the great advance that has occurred in understanding the phylogenetic relationships of component taxa of freshwater neotropical ichthyofauna, using mainly the family Characidae as a possible model. Finally, a recent intriguing idea of the role of respiratory physiology in determining both the maximum size of teleost fish and their patterns of environmental occupation is examined in relation to its possible effect in the evolution of South American stream ichthyofauna.