DNA sequence analysis of the ribosomal DNA ITS2 region for the Anopheles punctulatus group of mosquitoes.

The internal transcribed spacer 2 (ITS2) from the ribosomal DNA was sequenced and characterized for ten cryptic species in the Anopheles punctulatus group, the members of which are major vectors of malaria and filariasis in the south-west Pacific. The length of the ITS2 ranged from 549 bp to 565 bp and displayed levels of sequence variation ranging from 2.3% to 24.3% due mainly to indels of simple sequences. The GC content varied from 61.3% to 70.9%. These values were higher than those found in other cryptic species of mosquitoes and comparable only to members of the An. dirus complex suggesting a possible link between this group of Asian mosquitoes and the An. punctulatus group. Optimal and suboptimal secondary structures were investigated and revealed structures where the 5' region folded independently of the 3' region. Due to the large level of sequence variation between species, the ITS2 region proved unsuitable for phylogenetic analysis.