Abstract
Nucleotide sequences of the circadian rhythm genes, period and timeless, were studied for the first time in mosquitoes Culex pipiens Linnaeus, 1758. In this work we evaluated variations of the studied genome fragments for the two forms of Culex pipiens (forma “pipiens” – mosquitoes common for aboveground habitats, forma “molestus” – underground mosquitoes). We compared Culex pipiens from Russia with transatlantic Culex pipiens and subtropical Culex quinquefasciatus Say, 1823. Our results show that intraspecies variability is higher for the gene period than for the gene timeless. The revealed substitutions in nucleotide sequences and especially in amino acid sequences grouped the individuals of the two forms into distinct clusters with high significance. The detected fixed amino acid substitutions may appear essential for functioning of the circadian rhythm proteins in Culex pipiens, and may be correlated with adaptations of the taxa within the group Culex pipiens. Our results suggest that natural selection favors fixed mutations and the decrease in diversity of the genes period and timeless in mosquitoes of the Culex pipiens f. “molestus” compared with the Culex pipiens f. “pipiens”, is probably correlated with adaptive features of Culex pipiens f. “molestus”. The studied genome regions may be considered as promising molecular-genetic markers for identification, population and phylogenetic analysis of similar species and forms of the Culex pipiens complex.
Highlights
The Culex pipiens Linnaeus, 1758 complex considered by some authors as a ‘polytypic species’ includes up to seven morphologically identical or very similar forms (Harbach et al 1984, 1985, Vinogradova 2000)
Nucleotide sequences of the circadian rhythm genes were studied for the first time in mosquitoes C. pipiens f. “molestus” and compared with those for C. pipiens f. “pipiens” and C. quinquefasciatus
The results suggest that natural selection favored the fixed mutations and the decreased diversity of the genes per and tim in mosquitoes of the C. pipiens f. “molestus” compared with the C. pipiens f. “pipiens”
Summary
The Culex pipiens Linnaeus, 1758 complex considered by some authors as a ‘polytypic species’ includes up to seven morphologically identical or very similar forms (Harbach et al 1984, 1985, Vinogradova 2000). The specific features of reproduction and development of the two forms has resulted in their spatial isolation in moderate climate areas, suggesting genetic isolation This suggestion is confirmed by the isoenzyme analysis of autogenous and anautogenous populations of C. pipiens from England (Byrne and Nichols 1999), Russia (Lopatin 2000) and Germany (Weitzel et al 2009) as well as by study of populations from Europe with CQ11 assay (Bahnck and Fonseca 2006). The results of these investigations showed that in these regions the forms are genetically distinct, with no or poor gene flow between populations of different forms. The question of divergence of the two forms in moderate climates remains still unclear
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