A molecular test of alternative hypotheses of tetraodontiform (Acanthomorpha: Tetraodontiformes) sister group relationships using data from the RAG1 gene.

Two primary competing hypotheses regarding the identity of the sister group of the order Tetraodontiformes exist. The first hypothesis holds that some or all acanthuroid fishes represent the sister of Tetraodontiformes. The second, proposed in 1984 by Rosen, holds that the order Zeiformes is sister to Tetraodontiformes and that the family Caproidae is sister to this Zeiformes + Tetraodontiformes clade. These two hypotheses were tested using data from the single-copy nuclear gene RAG1. Representatives of most major orders of acanthomorph fishes were included to provide an appropriate context in which to place Tetraodontiformes and its hypothesized sister groups. The results of an unweighted parsimony analysis indicate that Zeiformes is not the sister group of Tetraodontiformes. In addition, Caproidae appears unrelated to Zeiformes. A monophyletic Tetraodontiformes was recovered as the sister group of the clade Ephippidae + Drepanidae and was more distantly related to the included zeiform and caproid representatives.