Several cichlids in South America should be considered part of the Mesoamerican heroine clade, according to a molecular study due to be published next month.
The heroine cichlids of the Mexican neovolcanic plateau are one of the few groups of vertebrates that are found either side of this geographical boundary, both in South America and in North America. However, little is known about how the plateau has been important in their evolution.
A group of scientists from the Center for Population Biology at the University of California - Davis, is due to publish a paper next month in the journal Molecular Phylogenetics and Evolution, based on a study of 52 of the 80 heroine cichlids in this region.
The paper claims: "Our analysis suggests several cichlids in South America should be considered as part of the Mesoamerican Heroine clade because they and the cichlids north of the Isthmus of Panama are clearly supported as monophyletic with respect to all other Neotropical cichlids.
We also recovered a group containing species in Paratheraps, Paraneetroplus and Vieja as the sister clade to Herichthys. Herichthys is the only cichlid clade north of the Mexican Plateau and it is monophyletic."
The workers say that it has taken approximately 6 million years for the divergence of Herichthys, which is comparable to the time it's taken for the toad genus Bufo, one of the few groups which shares this unusual geographic distribution.
More information: Darrin Hulsey C, Garcia De Leon FJ, Sanchez Johnson Y, Hendrickson DA, Near TJ. (2004) - Temporal diversification of Mesoamerican cichlid fishes across a major biogeographic boundary. Mol Phylogenet Evol. 2004 May;31(2):754-64.