Sequence, secondary structure and phylogenetic analyses of the ribosomal internal transcribed spacer 2 (ITS2) in the Timarcha leaf beetles (Coleoptera : Chrysomelidae)

Internal transcribed spacer 2 (ITS2) sequences of the nuclear rDNA in forty -seven specimens (thirty-four species) of the leaf beetle genus Timarcha ha ve been studied. Timarcha ITS2 (523 bp on average) share some sequence feat ures with other Chrysomeloidea relatives (Chrysolina, Diabrotica and Bruchu s) but have no clear similarity with any other arthropod ITS2 sequences. In terspecific divergences are in the range 0.002-0.166, and 0.124-0.206 in th e comparisons between subgenera. No evidence of intragenomic divergent ITS2 sequences has been found. Secondary structures are concordant with the fou r-domain model proposed for vertebrates and yeast, but differs from those p roposed for dipterans. Phylogenetic analysis of the ITS2 data confirms the results of a previous study based on mitochondrial sequences, as the basali ty of the Metallotimarcha subgenus and the absence of phylogenetic support for the Timarchostoma subgenus.