Testando o sistema de downloads com um artigo sobre a taxa de evolução cariotípica em Characiformes (Teleostei).
Rates of chromosomal changes in Neotropical Characiformes (Teleostei)
Rubens Pazza & Karine Frehner Kavalco
Current Topics in Genetics, vol 4, 2010: 11-19.
Despite of evidence pointing to the major role of chromosomal rearrangements in reproductive isolation processes, the correlation between karyotype evolution and speciation still remains an open question. In the present work, we estimated the rate of chromosomal changes in Neotropical Characiformes by calculating the number of reported karyotypes divided by the time of divergence of each group. Only the data regarding the karyotypic formulae were taken into account since cytogenetic markers are not available to all analyzed species. Therefore, the rate of chromosomal changes was estimated for 1,135 living species from 12 families of Characiformes. Each family presented distinct rates of chromosomal changes, reflecting the evolutionary trends observed in the literature. The highest rate of chromosomal changes was found in the family Characidae (5.65), while the lowest rate was observed in the family Ctenolucidae (0.02). The second family with the highest rate of karyotypic evolution is Erythrinidae, with just 0.45 different karyotypes per million years, very lower than that estimated for Characidae. However, Erythrinidae was the only family with a number of distinct karyotypes higher than the number of living species. Because of this feature, it was necessary to estimate a relative rate of chromosomal changes, thereby revealing that Erythrinidae is actually the Characiformes group with the highest rate of karyotypic changes. Divergent tendencies for the fixation of specific rearrangements might indicate the occurrence of distinct evolutionary mechanisms, associated with the life history of each fish group.