Comparative analysis of sequences and secondary structures of the rRNA internal transcribed spacer 2 (ITS2) in pollen beetles of the subfamily Meligethinae (Coleoptera, Nitidulidae): potential use of slippage-derived sequences in molecular systematics.

ABSTRACT

A comparative analysis of ITS2 sequences and secondary structures in 89 species of pollen beetles of the subfamily Meligethinae (Coleoptera, Nitidulidae) was performed. The ITS2 folding pattern was highly conserved and comparable with the general model proposed for eukaryotes. Simple sequence repeats (SSRs) were responsible for most of the observed nucleotide variability (approximately 1-3%) and length variation (359-459bp). When plotted on secondary structures, SSRs mapped in expansion segments positioned at the apices of three ITS2 helices ('A', 'B' and 'D1') and appeared to have evolved under mechanisms of compensatory slippage. Homologies among SSRs nucleotides could not be unambiguously assigned, and thus were not useful to resolve phylogeny. However, slippage-derived motifs provided some preliminary genetic support for newly proposed taxonomic arrangements of several genera and subgenera of Meligethinae, corroborating existing morphological and ecological datasets.