Study unravels Cichlasomatini relationships

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Scientists from the Czech Republic have conducted the first comprehensive molecular phylogeny of the South American cichlid tribe Cichlasomatini, publishing their results in the latest issue of the journal Molecular Phylogenetics and Evolution.

Zuzana Musilov, Old ich ~an, Karel Janko and Jind ich Novk analyzed sequences for 41 species of cichlasomatine cichlids (consisting of members of the genera Acaronia, Aequidens, Bujurquina, Cichlasoma, Cleithracara, Ivanacara, Krobia, Laetacara, Nannacara and Tahuantinsuyoa).

They used a total of 2236 base-pairs of sequences from two mitochondrial (16S rRNA and cytochrome b) and one nuclear (first intron of S7 ribosomal gene) markers.

The authors confirm that Aequidens is paraphyletic (not a natural group), with some of its members (the Guyanan river species A. potaroensis and A. paloemuensis) more closely related to Krobia than to other Aequidens.

As a result of this study, three suprageneric natural groups (clades) were identified: the Aequidens (Cichlasoma) clade, the Bujurquina"Tahuantinsuyoa"~Aequidens clade and the Cleithracara"Nannacara"Ivanacara clade.

The results differ considerably from earlier published morphology-based phylogenies of the group, being similar in only one point (the close relationship of Nannacara+Ivanacara and Cleithracara).

The authors also studied the historical biogeography of the group, and concluded that he dating of age and initial divergence within Cichlasomatini is placed around 44 , which is in good agreement with the independently estimated age of heroines, the cichlasomatine sister group

Although the colonization of Mesoamerica by the only cichlasomatine species (~Aequidens coeruleopunctatus) likely followed the same route from trans-andean South America, it happened much more recently, after the separation from the remaining species at around 10 MyaAll six ~Aequidens species are primarily trans-andean, including the putative sister group of ~A. pulcher (A. latifrons), which was not available for analyses.

~Aequidens pulcher is thus the only species of the group that is secondarily found also in cis-andean South America (Orinoco river Basin in Venezuelan llanos and on Trinidad). Based on our analyses this secondary dispersal into cis-andean South America and vicariance from trans-andean relatives is dated at ca. 10

For more information, see the paper: Musilov, Z, O ~an, Kl Janko & J Novk (2008) Molecular phylogeny and biogeography of the Neotropical cichlid fish tribe Cichlasomatini (Teleostei: Cichlidae: Cichlasomatinae). Molecular Phylogenetics and Evolution 46, pp. 659"672.