Padrões da evolução cariotípica da família cichlidae sob contexto global: regularidades biogeográficas e especificidades citogenômicas

Abstract

The family Cichlidae is one of the most diverse groups of fish, comprising nearly two thousand species globally distributed across the river basins of the Americas, Africa, Madagascar, India, Sri Lanka, and the Middle East. The diversification of this group is attributed both to extensive processes of allopatric speciation and rapid radiative bursts of sympatric speciation. Although many cytogenetic aspects of this family have been studied, the relationship between biogeographic and phylogenetic diversification processes and karyotype evolution remains less understood. In this context, comparative cytogenomic analyses were conducted on a significant set of multicontinental species from the Cichlidae family to contribute to understanding the evolutionary trends associated with biogeography and its diversification processes. Chromosomal patterns were conspicuously differentiated between Neotropical species groups (Central and South America) and Afrotropical species groups (Africa), regions that host the highest species diversity. The modal diploid value for Neotropical species reflects a basal condition with 48 chromosomes, accompanied by notable structural variation in karyotypes. In contrast, Afrotropical species exhibited reduced karyotypes with 2n=44 and greater structural similarity among their karyotypes, as well as unique features in the organization of repetitive DNA sequences. Multiple and sometimes syntenic rDNA sites, alongside other repetitive sequences, suggest intense internal chromosomal reorganizations. The biogeographic context of cytogenetic diversification indicates that extensive allopatric partitioning, involving rivers in Central America and the Amazon basin in South America, drives significant structural changes in karyotypes, influencing the evolution of these species. Conversely, rapid sympatric adaptive radiation processes, driven by ecological partitioning in the large African lakes, have promoted the retention of significant karyotypic conservatism among Afrotropical species.