Phylogenetic relationships between the families of the infraorder Culicomorpha were investigated by using partial 28S ribosomal RNA gene sequences. All families traditionally placed in this infraorder were investigated and confirmed as clades. On the other hand, some of the morphological relationships between these families were found to be in disagreement with phylogenies based on molecular characters. Our results did not support the generally accepted division of the Culicomorpha into two superfamilies, the Culicoidea (Culicidae ϩ Corethrellidae ϩ Chaoboridae ϩ Dixidae) and the Chironomoidea (Chironomidae ϩ Ceratopogonidae ϩ Simuliidae ϩ Thaumaleidae). Precisely, if the sister-group relationship between Culicidae, Chaoboridae and Corethrellidae was clearly confirmed, the Dixidae, traditionally considered as closely related to these two families, were not placed close to them on our trees. On the other hand, strong evidence was found for grouping together the Simuliidae and the Thaumaleidae, in spite of the cytological and morphological differences between these two families. The position of the Ceratopogonidae was uncertain, and the Chironomidae appeared as a possible sister group to the rest of Culicomorpha. The phylogenetic positions of the groups characterized by feeding on vertebrate blood or insect haemolymph (the Culicidae, Chaoboridae, Ceratopogonidae and Simuliidae) suggest that haematophagy has appeared at least twice in the evolution of Culicomorpha.

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The complete set of available ribosomal proteins was utilized, at both the peptidic and the nucleotidic level, to establish that plants and metazoans form two sister clades relative to fungi. Different phylogenetic inference methods are applied to the sequence data, using archeans as the outgroup. The evolutionary length of the internal branch within the eukaryotic crown trichotomy is demonstrated to be, at most, one-tenth of the evolutionary length of the branch leading to the cenancester of these three kingdoms.