Karyotype and mitochondrial 16S gene characterizations in seven South American Cichlasomatini species (Perciformes, Cichlidae)

The family Cichlidae constitutes most of the freshwater fish fauna of South America; its taxonomy is at present mainly based on morphological characters. Here, relationships among seven Cichlasomatini species have been investigated by studying their karyotype structure and by sequencing a 520 bp fragment of the mitochondrial 16S gene. Molecular data sets point to a high affinity of Cichlasoma amazonarum with Aequidens sensu stricto group, in particular with Aequidens tetramerus. Aequidens never form a single monophyletic clade: molecular trees group together ‘Aequidens pulcher’ and ‘Aequidens rivulatus’ and suggest their close relationship with Bujurquina and Laetacara, rather than with the A. sensu stricto group. Both molecular and karyotypic data confirm that Cleithracara maronii belongs to a distinct clade, thus supporting its generic differentiation based on morphological characters. Chromosome number, karyotype structure and molecular data suggest that Laetacara dorsigera is related to Bujurquina vittata and confirm their generic level of differentiation. From a cytotaxonomic point of view, a karyotype of 2n = 48 with most acrocentric or subacrocentric chromosomes could be the ancestral one from which the others might have derived.