Intron insertion as a phylogenetic character: the engrailed homeobox of Strepsiptera does not indicate affinity with Diptera

The phylogenetic relationships of the order Strepsiptera are unclear. Affil iation to Coleoptera has been proposed, however this implies that dipteran halteres and strepsipteran haltere-like organs evolved convergently. An alt ernative is a sister group relationship with Diptera, In this case, haltere s could be homologous but a radical homeotic mutation may have switched the ir position to the Strepsipteran mesothorax. Ribosomal DNA sequence analysi s has been used to support Dipteran affiliation, although this is controver sial. Here we investigate the potential of an intron insertion site as a ph ylogenetic character. We! find that the en homeobox gene of the strepsipter an Stichotrema dallatorreanum lacks a derived intron insertion shared by re presentatives of Diptera and Lepidoptera, We argue against a close affiliat ion between Strepsiptera and Diptera.