Karyotypic evolution in cichlids (Cichlidae; Percomorpha): biogeographic context and role in reproductive isolation
Karyotypic evolution, chromosomal rearrangements, rDNA, allopatric speciation, sympatric speciation.
The Cichlidae family, extensively distributed in hydrographic regions of the Americas, Africa, Madagascar, India, Sri Lanka and the Middle East, exhibits one of the most notable examples of diversification among fish, whose more than 1700 species result from both long processes in allopatry and of rapid sympatric radiation explosions. Although cytogenetic aspects of the group have been evaluated, the understanding of how the processes of biogeographic and phyletic diversification are associated with the evolution of the karyotype is less known. In this context, comparative cytogenetic analyzes of 21 intercontinental species of the Cichlidae family were carried out here, using conventional and molecular cytogenetic techniques, with a view to identifying karyotypic aspects associated with the historical biogeography of the group and estimating the role of karyotypic diversification in post-reproductive isolation zygotic, through cytogenetic analysis of artificial hybrids. The cytogenetic patterns were different between species from the American and African continents, geographic scenarios of greater diversification of cichlids. The modal value 2n presented on the American continent was 48 chromosomes, and 2n=44, in African species. The data indicate that allopatric speciation processes, involving the Amazon and Central American rivers, account for greater structural diversification in karyotypes, while rapid sympatric processes of adaptive radiation, occurring in large lakes, retain significant karyotypic conservatism in African species