Secondary structure and sequence variation of the 28S rRNA gene in the Neanuridae, and its utility as a phylogenetic marker

A fragment of the 28SrRNA encompassing the divergent domains D1-D5 was sequenced in 14 species of Collembola Neanuridae, 12 of which belong to the subfamily Neanurinae. A slight length variation across taxa was found in the D2, D3 and D5 divergent domains, the core regions being very conserved in length and sequence. Nucleotide composition was slightly biased towards As and Ts (55.6%), with the bias being more evident in the nucleotides not involved in pairing with complementary sequences. A+T bias was higher in the divergent domains than in the core regions. The number of variable sites was high in the divergent domains, and positively correlated to their length, with the D2 domain being the longest and the most variable one. Phylogenetic analysis strongly suggested monophyly of the Neanurinae and less strongly of the Neanurini. It also suggested polyphyly of the genera Neanura and Deutonura. Some relationships are in contrast with morphological evidences, but are in agreement with molecular data from the mitochondrial COII gene.