Molecular phylogeny of the apterygotan insects based on nuclear and mitochondrial genes

Basal hexapodan orders (Apterygota) are traditionally divided in two well d efined taxonomic groups, Entognatha and Ectognatha. Entognathy (the enclose d mouthparts condition) is considered the most distinctive character joinin g the Ellipura (Protura+Collembola) with the order Diplura, whereas the pre sence of exposed mouthparts (ectognathy) is the feature shared by Microcory phia and Zygentoma with the pterygote insects. In spite of the growing inte rest for the evolutionary history of the Apterygota, there is no complete a greement among the general phylogenetic hypotheses based on the study of mo rphological characters. In this study we analyzed the DNA sequence of segme nts of the nuclear Elongation Factor-1 alpha (EF-1 alpha) and of the mitoch ondrial 12S rRNA genes, and used different methods of phylogenetic reconstr uction. The 12S gene seems to be more suited than the EF-1 alpha to resolve some of the most outstanding systematic disputes, whereas the lack of reso lution at the deeper nodes does not allow to assess the phylogenetic relati onships within Microcoryphia and between ectognathan orders. We have obtain ed a fairly high support for the monophyly of the orders Diplura and Zygent oma. In the 12S analysis, the Ellipura and the Entognatha form monophyletic assemblages. In addition, the study of the distribution of introns in the EF-1 alpha suggests a relationship between Collembola and Diplura.