A molecular biologist has used a modern molecular technique to try and determine how a number of fish in the Cichlasomatini tribe are interrelated.
Marescalchi looked at karyotype and mitochondrial 16S gene characterisations in seven South American Cichlasomatini species, including fish in the Aequidens, Cleithracara, Bujurquina, Cichlasoma and Laetacara genera.
Most previous studies of this group of cichlids has looked at morphological data, so new molecular studies, like this one, can shed new light on parts of the phylogeny which scientists haven\'t been able to completely unravel.
Marescalchi found that there is a close relationship between Cichlasoma amazonarum and the Aequidens sensu stricto group, with Aequidens tetramerus appearing very closely related.
However, the Aequidens group looks like it could be in line for some potential reshuffling in the future, as this study also found that it wasn\'t monophyletic. Instead, it includes groups of fish which have descended from separate but closely related fishes.
The genetic data gathered was used to produce evolutionary family trees, called phylogenies, which showed that \'Aequidens pulcher\' and \'Aequidens rivulatus\' are closely related to each other, and also to Bujurquina and Laetacara, rather than with the Aequidens sensu stricto group.
The Keyhole cichlid, Cleithracara maronii, which was moved to a genus of its own a few years ago, appears to be in the right place, as this data shows that it\'s more distantly related to other cichlasomatines.
Marescalchi says that a number of other data suggest a close relationship between Laetacara dorsigera and Bujurquina vittata but supports the move to keep each in a genus of its own.
For more details see the paper: Marescalchi, O (2005) - Karyotype and mitochondrial 16S gene characterizations in seven South American Cichlasomatini species (Perciformes, Cichlidae). Journal of Zoological Systematics & Evolutionary Research, 43: 22-28.